Article: Information on the treatment of alcoholic wastewater

This post was last edited by hesonchang214 on 2009-8-30 03:29. Topic: Engineering for the treatment of alcohol distillate waste using solid-liquid separation – UASB-SBR technology. Source: China Thesis Download Center. Authors: Tian Ningning, Wang Kaijun. Editor: studa9ngns. Abstract: This paper discusses the treatment technologies for alcohol distillate waste from potato-based distilleries, and proposes a treatment process that utilizes belt filter press for solid-liquid separation followed by UASB-SBR technology. An application example from a winery is used to illustrate the engineering design scheme, the debugging process, and the treatment results. Keywords: potato chip distillation, alcohol leachate, solid-liquid separation – UASB-SBR, belt filter press. The alcohol industry is an important basic raw material industry for the national economy. Alcohol is widely used in fields such as chemistry, food, daily chemicals, and medicine and health. China’s annual alcohol production is around 3 million tons, with grains (such as corn and dried potatoes) serving as the main raw materials. Approximately 80% of grain-based alcohol is produced from dried potatoes. The alcohol waste liquor discharged during the distillation step in the alcohol production process is an organic waste liquid with high levels of suspended solids and a high concentration. According to statistics, over 500 kg of organic matter is emitted for every 1 ton of alcohol produced. The annual discharge of wastewater from the alcohol industry nationwide');"> amounts to about 12 million cubic meters. If large amounts of high-concentration organic wastewater are discharged directly without proper treatment, it will cause severe pollution. Resource waste and environmental pollution have become important factors restricting the development of the domestic alcohol industry. 　　Anhui Sizhou Winery is a liquor factory that produces alcohol using dried potatoes as raw material, with an annual output of 5,000 tons of alcohol. During normal production, 250 m3/d of alcohol lees are discharged, with a temperature of 90°C for the lees. The wastewater mainly contains sugars, organic acids, proteins, and cellulose, etc. The concentration of organic substances is very high, with CODCr ranging from 30,000 to 45,000 mg/L and BOD5 ranging from 15,000 to 25,000 mg/L. The sludge liquor is very turbid, with an SS of approximately 40,000 mg/L. The waste liquid is acidic, with a pH of 3–4. Although alcoholic distillers’ grains have high concentrations of pollutants, they are non-toxic and exhibit good biodegradability. This factory is part of the projects for targeted remediation in the Huai River basin. To completely eliminate the severe pollution it causes to the surrounding environment and groundwater resources, the plant has carried out comprehensive utilization of distiller’s grain waste liquid, constructing a treatment facility for high-concentration organic wastewater (distiller’s grain liquid) with a processing capacity of 250 m3/day. Feed in the spent liquor is recovered simultaneously, along with biogas production. 　　The design wastewater quality parameters are: CODCr: 40,000 mg/L ； BOD5: 25000mg/L ； SS: 20,000 mg/L ； pH: 3.5～4. The quality of the water discharged after treatment should meet the Class 1 standards specified in the \"Integrated Wastewater Discharge Standards\" (GB8978-88): CODCr: ＜350mg/L ； BOD5: ＜200mg/L ； SS: ＜200mg/L ； pH: 6–9. 1 Selection of treatment process One of the keys to the comprehensive utilization and advanced treatment of alcohol distillers’ waste liquid is the effective separation of solids from liquids in this waste liquid. Dehydrating potato chip alcohol waste liquid is a very challenging task. In the past, centrifugal dehydrators and box filter presses were used for such dehydration attempts. Due to the high viscosity and small particle size of this waste liquid, it easily clogs the filters of centrifugal dehydrators and the filter cloths of box filter presses, resulting in unsatisfactory outcomes. Therefore, it cannot be applied to the dehydration of potato chip distillers’ grains liquor. 　　The Environmental Protection Institute of the former Ministry of Machinery conducted in-depth research on the dehydration process for alcohol waste liquid, and developed a new type of belt filter press (see Figure 1). The features of the new belt filter press are as follows: ① Ultra-long gravity dewatering zone ； ②Ultra-long inclined wedge area ； ③Compact press area with increasing pressure ； ④Original filter band offset detection method and dual-end correction mechanism ； ⑤A backwashing method with good performance and high efficiency. Figure 1 Working principle of the new type belt filter press: 1. Press; 2. Reactor; 3. Flow meter; 4. Instant dissolver; 5. Chemical dosing pump; 6. Feeding pump; 7. Air compressor; 8. Flushing pump; 9. Conveyor. Results from industrial tests conducted in a brewery showed that the feed alcohol lees had a moisture content of 96%–96.5%, a pH value of 4.0, and a temperature of 70°C. The moisture content of the distillers’ grain filter cake after dehydration is 72%. Using a belt filter press for the dehydration of alcohol distillers’ grains is an attempt and a breakthrough. The key technical aspect lies in devising targeted methods for adjusting the isoelectric point and corresponding flocculation processes, which can increase the recovery rate of distillers’ grains and the removal efficiency of CODCr from the distillers’ grain liquid (74%), thereby having a significant effect on reducing the load associated with the advanced treatment of the effluent. 　　After solid-liquid separation of the wine lees wastewater using a belt filter press, the CODCr level of the filtrate can be reduced by about 50%, and the SS level also decreases significantly, which facilitates the anaerobic and aerobic biological treatment of the wastewater. The subsequent anaerobic process uses an Upflow Anaerobic Sludge Blanket (UASB), while the aerobic process employs a Sequential Batch Reactor (SBR). 2 Introduction to the treatment process The core of this process consists of solid-liquid separation, UASB, and SBR. The distillers’ grain waste liquid passes through a coarse grid and enters a regulation tank where it is cooled and adjusted. Then, a vertical sludge pump is used to transfer this liquid to a sludge concentration tank; the concentrated liquid subsequently goes into a belt filter press for solid-liquid separation. The filter residue can be processed through extrusion and drying to produce feed ready for sale. The filtrate is pumped into anaerobic UASB and aerobic SBR units for treatment, so that the effluent meets discharge standards. The biogas produced by UASB passes through a water-sealed flame arrester before entering the gas storage tank or being sent to the plant’s boiler for direct combustion (see Figure 2). Figure 2 Process flow for treating alcohol waste liquid at Sizhou Winery 3 Design of main treatment structures and equipment 3.1 Regulating sedimentation tank The regulating sedimentation tank is an underground structure with overall dimensions of 10 m in length, 4.5 m in width, and 3.0 m in depth, and a hydraulic retention time of 2.0 hours. A sludge hopper is installed at the bottom of the regulating tank; the inclination angle of this hopper is 50°. A sludge lift pump is placed inside the hopper to lift the settled sludge to the thickening tank. Two anaerobic feed pumps are installed in the shallow area of the regulating tank, one in use and one as a backup. 3.2 UASB Reactor After solid-liquid separation of the distiller’s grain waste liquid, 50% of the CODCr is removed; the CODCr level of the water entering the UASB reactor is 20,000 mg/L, with a flow rate of Q = 225 m3/d. The design load is 7.0 kgCODCr/(m3·d), with a digestion temperature of 35–37°C. The UASB reactor tank has a diameter of D=11m, a height of H=8.0m, and an effective water depth of H=**m. The UASB is equipped with a three-phase separator for supplying water and separating sludge and gas, in order to maintain a highly active anaerobic sludge community within the reaction tank and to effectively recover biogas. The CODCr level of the effluent from the UASB is ≤3000 mg/L, while the SS level is ≤1,500 mg/L. Its biogas production is 2,000 m3/day. 3.3 In the SBR reactor, the inlet CODCr level is ≤3000 mg/L, and the SS level is ≤1500 mg/L. The sludge load is 0.3 kg COD/(kg MLSS·day), the sludge concentration is 3 g/L, and the effective volume of the SBR reactor is 750 m3. Two circular SBR reactors are installed in accordance with the requirements of the wastewater treatment process. The dimensions of each SBR reactor are: D=11m, H=5.0m, with an effective water depth of 4.5m. 　　Different operating cycles are determined based on the operating patterns and design requirements of the SBR reactor. The drainage is carried out using a grating type drain, with its elevation controlled by a timer to facilitate drainage. 　　The aeration system uses medium-porosity aerators; assuming an oxygen utilization rate of 10% for these aerators and a CODCr removal efficiency of 90% in the aeration tank, the air supply volume should be 10 m3/min. Three SSR100 fans are selected, with two in use and one as a backup. 3.4 Fan Room Three SSR100 centrifugal fans are installed in the fan room, with 2 in use and 1 as a backup. The air volume per unit is 6.73 m3/min, with H=5.0 m. 　　The fan room is equipped with a sound-insulated power distribution room and an operation rest area. The total dimensions of the fan room are: length × width × height = 10m × 5m × 7m. 3.5 Sludge Thickening Tank After the distillers’ grain liquid enters the adjustment sedimentation tank, most of the sludge settles in the sludge hopper; it is then pumped to the sludge thickening tank for thickening, thereby facilitating subsequent mechanical dewatering of the sludge. The sludge thickening tank is of semi-underground reinforced concrete structure, with geometric dimensions of D×H = 5.0m×7.0m. 　　The concentrated sludge is fed into a belt filter press for mechanical dewatering, while the supernatant from the concentration tank is returned to the adjustment tank before being sent to a UASB anaerobic reactor for treatment. 3.6 Sludge Dewatering Machines and Dewatering Rooms The concentrated waste liquid and sludge are pumped using slurry pumps to a pipeline mixer, where they are mixed with polymer flocculants and coagulants. After reacting in a folded-plate flocculation reactor, they are sent to a belt filter press for dewatering. In this design, a belt filter press with a width of 1.5 m is used, having a processing capacity of 13.5 m3 of wet sludge per hour. The filtrate from the dehydrator is returned to the regulation tank and then sent to the UASB for further treatment. The tap water and air used for backwashing the belt filter press are supplied by a centrifugal pump and an air compressor. The dewatered sludge cake (with a moisture content of 80%) has high nutritional value. The chemicals used in this process have been shown through pharmacological tests and feeding trials to be non-toxic and harmless to livestock; therefore, the sludge cake obtained from the belt filter can be used directly as feed. At a cost of 500 yuan per ton of feed (dry matter), and assuming 300 working days per year, the annual revenue would amount to 1.2 million yuan. 　　The sludge dewatering plant consists of a machine room, a power distribution room, and a control room. It is equipped with 1 belt filter press with a bandwidth of 1.5 m, along with auxiliary equipment such as sludge pumps, chemical dissolving tanks, and air compressors. The floor dimensions of the dewatering room are L×B = 12.0 m×5.0 m, with a ceiling height of 5.0 m; the structure is brick-concrete. Solid-liquid separation – UASB-SBR technology for treating alcohol distillers’ waste liquid. Source: China Thesis Download Center. Authors: Tian Ningning, Wang Kaijun. Editor: studa9ngns. 4. Operation and adjustment as well as treatment efficiency. The commissioning of the plant starts with the anaerobic section and is carried out in three stages: sludge acclimatization period, load increase period, and full-load operation period. Commissioning of the anaerobic section began in October 1997, and by April 1998 all the alcoholic wastewater was fed into the UASB reactor. The organic load reached 8.0 kg CODCr/(m3·d), with the CODCr removal rate remaining stable at over 90%; the CODCr concentration in the effluent was around 2500 mg/L, while the SS concentration was around 1500 mg/L. In March 1998, the aerobic system was also put into operation, and after 3 months of operation, all indicators met the required standards. 　　First stage: Sludge acclimatization period – Anaerobic sludge from the anaerobic treatment system of the Lingbi Winery in a neighboring county is used for inoculation; after inoculation, the sludge concentration in the reactor is approximately 20.0 g/l. Since the water quality and fermentation temperature in the two plants are similar, there is no need to acclimate the sludge, thereby reducing the startup time. The anaerobic tank is raised from 20°C to 37°C, with a temperature increase of 1–2°C per day. A small amount of the high-temperature wastewater from the regulating tank is pumped into the anaerobic tank, while the excess wastewater flows out, thus enabling a heating cycle. Control the water inflow rate at 4–6 m3/h. At the same time, wastewater is added at a volumetric load of 0.1–0.3 kg CODCr/(m3·d). When the temperature rises to 37°C and the load reaches 2 kg CODCr/(m3·d), the stage of increasing the load begins. 　　Second stage: load increase period – On the basis of stable operation of the reaction tank, the load is increased from 2 kg CODCr/(m3·d) to the design load of 7.0 kg CODCr/(m3·d). During the acclimation period, water is added intermittently twice a day, with the load controlled based on concentration and volume. It is required that the volatile organic acids (VFA) in the effluent from the reaction tank be less than 200 mg/L, the pH be above 7.2, the CODCr removal rate be over 80%, and gas production be normal, before the load can be increased further. The entire commissioning period lasted about 7 months (4 months in the first phase and 3 months in the second phase). Once the UASB reached its designed capacity in April 1998, the CODCr removal rate remained above 90%. Although water quality fluctuates, the organic load remains consistently above 7.0 kg CODCr/(m3·d). As the organic load increases, the gas production also increases accordingly, with a gas production rate of 2.6–3.7 m3/(m3·d). The commissioning of an SBR aerobic reactor is relatively simple. First, clean water and a small amount of waste liquid are injected into the reactor to start aeration; once sludge has formed, the amount of waste liquid is gradually increased. Full capacity operation was achieved starting in March 1998, with a CODCr removal rate of over 90%, and the effluent quality met the specified discharge standards. 　　From May 19 to 21, 1998, the Anhui Provincial Environmental Monitoring Center conducted tests on the wastewater generated by a wine factory during its production process. The results showed that the average concentrations of CODCr and SS, as well as the pH value and the amount of wastewater produced per ton of alcohol, in the wastewater from Sizhou Wine Factory met the relevant requirements set out in the \"Integrated Wastewater Discharge Standards\" (GB8978-88) for fermentation and brewing industries. References 1 Wang Kaijun. Reconsideration of the anaerobic (hydrolysis)-aerobic treatment process. Chinese Journal of Environmental Sciences, 1998, 18(4): 337–340. 2 Du Bing et al. Research on the operation of UASB in the treatment of alcohol wastewater. China Biogas, 1999, 17(2): 14–17. 3 Zhang Deqing. Discussion on the engineering design for treating waste liquor from potato-based alcohol production. Water Supply and Drainage, 1999, 25(7): 34–36. Reposted from China Thesis Download Center: http://www.studa.net

Highly Efficient Anaerobic Technology for Treating Alcohol Wastewater – MIC Reactor Xu Fu, Wu Jianhua, Liu Feng, Jiang Jingdong, Ma Sanjian (Institute of Environmental Protection and Applied Technology, Suzhou University of Science and Technology, Suzhou 215011, Jiangsu, China) Abstract: In view of the high COD, high temperature, high SS, and low pH characteristics of alcohol wastewater, this paper mainly analyzes the water quality of such wastewater as well as its discharge conditions. After the proteins in alcoholic wastewater are extracted to produce DDG feed, a two-stage anaerobic and two-stage aerobic treatment process using a medium-temperature MIC anaerobic reactor and a Carrousel oxidation ditch is employed, enabling the effluent to meet **secondary discharge standards. It was also shown that when the anaerobic temperature is maintained at 35–37°C, the pH is around 4–5, and the organic load is 15 kgCOD·m-3·d-1, the COD removal rate in the MIC reactor exceeds 88%, allowing it to operate stably over the long term. Keywords: alcoholic wastewater ； MIC reactor ； Preprocessing ； Oxidation ditch. Chinese Library Classification Number: Document Code: Article Number: The High-Efficiency Anaerobic Technology for Alcohol Wastewater Treatment —— MIC Reactor XU Fu, WU Jian-hua, LIU Feng, JIANG Jing-dong, MA San-jian (Institute of Environmental Protection Application Technology, USTS, Suzhou 215011) Abstract: Considering the characteristics of alcohol wastewater, such as high COD, high temperature, high SS, and low pH, an analysis was conducted on the quality of this wastewater as well as its discharge conditions. After removing DDG, the MIC reactor and the oxidation ditch were used as the secondary anaerobic and secondary aerobic treatment processes respectively. As a result, the effluent met the second-class discharge standards. Before entering the MIC anaerobic reactor, the wastewater was cooled to 35–37 ℃, and alkali was added to adjust its pH. It then entered the MIC reactor for treatment. When the COD concentration of the incoming wastewater was around 15 kgCOD·m-3·d-1, the COD removal rate remained above 88%, allowing the MIC reactor to operate stably. Keywords: Alcohol wastewater; MIC anaerobic reactor; Pretreatment; Oxidation ditch. Alcohol is produced from materials such as corn, sweet potatoes, and wheat. For every 1 ton of alcohol produced, 13–15 tons of process wastewater are generated. This wastewater features high COD, high temperature, high SS, and low pH, making it high-concentration organic wastewater. A alcohol plant with a capacity of 20*104 tons per year generates approximately 300 tons of COD as waste per day; this is equivalent to the daily wastewater output from a city with a population of around 800*104 people. If this wastewater is not treated in a stable and reliable manner, it will inevitably cause severe damage to the environment. Anaerobic biological treatment of wastewater can not only degrade organic matter but also produce a certain amount of biogas. Increasing the organic load in anaerobic reactors and ensuring their stable operation have always been driving forces behind the development of anaerobic technologies. To reduce the investment, energy consumption, and operating costs associated with wastewater treatment, as well as to improve the comprehensive utilization of alcoholic wastewater, several new processes and equipment have been developed. The MIC anaerobic reactor is a highly efficient multi-stage internal circulation anaerobic reactor that was developed based on the principles of the IC reactor. Based on the characteristics of alcoholic wastewater, this paper proposes an efficient, energy-saving, advanced, and stable wastewater treatment process, and focuses on the design, commissioning, and operation of the MIC anaerobic reactor. 1 Alcohol production and wastewater issues 1.1 Brief description of the alcohol production process The fermentation of starchy raw materials is the main method used in China for alcohol production. Agricultural by-products containing starch serve as the primary raw materials; starch is the fermentable substance in these materials. Yeast cannot directly use starch to produce alcohol, so in order to produce alcohol from starchy raw materials, it is necessary to crush the raw materials first, thereby breaking down the plant cell structures and facilitating the release of starch. Through cooking, the starch is gelatinized and liquefied, and the cells are broken down to form a homogeneous fermentation broth, which allows it to be more readily acted upon by enzymes and converted into fermentable sugars. The main chemical reaction in its production process is saccharification: (C6H10O5)n (starch) + nH2O → C6H10O6 (glucose) ； Fermentation: C6H10O6→2C2H6O (alcohol) + 2CO2↑ + heat. 1.2 Alcohol wastewater situation: The wastewater generated in alcohol production mainly comes from the alcohol residue liquid discharged after distilling the fermented mash, as well as from the washing water and rinsing water used for production equipment, as well as the cooling water used in the processes of cooking, saccharification, fermentation, and distillation. The water quality of alcohol lees, washing water, and cooling water, as well as the wastewater volume per ton of product, are shown in Table 1. Table 1 Water quality and wastewater discharge volume per ton of product for alcohol distillate residues, washing water, and cooling water.
Wastewater name | Discharge volume/t·t-1 | Product pH | COD/mg·L-1 | BOD5/mg·L-1 | SS/mg·L-1
Alcohol distillate residues | 13–16 | 4–4.5 | 5–7*10^4 | 2–4*10^4 | 1–4*10^4
Residual water from the distillation tower | 3–4 | 5.0 | 1000 | 600
Washing water | 2–4 | 7.0 | 600–2000 | 500–1000
Cooling water | 50–100 | 7.0 | ＜100
Alcohol distillate residues are high-concentration organic wastewater; the main pollutants in them include solid insolutes suspended in the wastewater, oils, starch, and gums ； Sugars, acids, bases, salts, etc. dissolved in water ； The temperature can reach around 100°C ； The suspended solids content is high, with organic matter accounting for 94%–95% and ash accounting for only 6%–7% ； It has a turbid appearance, high color intensity, and is prone to **. 1.3 Design requirements for water quality and discharge: In a corn alcohol plant in Anhui with a capacity of 20*104 t/a, the alcohol distillate waste liquid is separated by pressure filtration; the filter residue is used as DDG feed, while the filtrate needs to be treated and biogas recovered. The water quality characteristics and discharge requirements for this wastewater are shown in Table 2. Table 2: Wastewater quality parameters and discharge requirements
| Parameter | Value | Unit |
|-----------|-------|------|
| Water volume / m³·d⁻¹ | 6000 | |
| pH | 3–4 | |
| COD | 30,000 | mg·L⁻¹ |
| BOD₅ | 35,000 | mg·L⁻¹ |
| Temperature / °C | 20,000–30,000 | |
| SS | 55–65 | mg·L⁻¹ |

Wastewater quality: 6000; pH: 3–4; COD: 30,000 mg·L⁻¹; BOD₅: 35,000 mg·L⁻¹; Temperature: 20,000–30,000 °C; SS: 55–65 mg·L⁻¹

Discharge requirements (GB8978-1996, Class II): 6–9; COD ≤ 150 mg·L⁻¹; BOD₅ ≤ 30 mg·L⁻¹; Temperature at normal conditions ≤ 150 °C

Wastewater treatment process: 2.1 Pretreatment of alcohol wastewater
(1) Solid-liquid separation to produce DDG feed. High levels of SS in alcohol wastewater can affect the proper operation of anaerobic reactors and reduce their efficiency. This disrupts the dynamic balance of anaerobic microorganisms, leading to excessive growth of hydrolytic and acid-producing bacteria. As a result, organic acids accumulate, which inhibits the metabolism of methanogenic bacteria and limits the conversion of organic acids into methane. This reduces the amount of biogas produced and increases the risk of “acidification” in the reactor. Plate and frame filtration is used to separate the solid proteins from the wastewater in order to produce DDG feed; the market price of each 1 ton of DDG feed is around 600–800 yuan. This approach allows for resource recovery, reduces the operational risks associated with anaerobic reactors, and improves their efficiency. (2) Medium-temperature anaerobic treatment and cooling with plate heat exchangers: Temperature is an important parameter affecting the anaerobic biological treatment process. It influences the activity of certain enzymes within anaerobic microbial cells, which in turn affects the growth rate of these microorganisms as well as their metabolic rate regarding the substrate; this ultimately impacts the activity of the anaerobic sludge and the organic load. The anaerobic biochemical rate reaches a maximum around 35°C, then drops to a low level at around 45°C, before reaching another maximum between 53–63°C; the temperatures corresponding to these two maxima represent the mesophilic and thermophilic anaerobic conditions, respectively. However, under high-temperature conditions, the net biological productivity of anaerobic bacteria is low, being half that at moderate temperatures; this results in a longer startup time for anaerobic processes at high temperatures, poor adaptability to changes in substrate and toxicity, and unstable operation] Therefore, when using medium-temperature anaerobic treatment for alcohol wastewater, a plate heat exchanger is required to cool the wastewater. Such heat exchangers offer high heat transfer efficiency, occupy less space, are lightweight and easy to install or remove, while also helping to reduce odor pollution in the factory area. 2.2 Anaerobic treatment of alcoholic wastewater The anaerobic digestion process has evolved over time, incorporating technologies such as anaerobic filters, Upflow Anaerobic Sludge Blanket (UASB) reactors, anaerobic expanded bed reactors, anaerobic fluidized bed reactors, anaerobic bioreactors, anaerobic baffled reactors, and Expanded Granular Sludge Bed (EGSB) reactors. Building on the foundation of the efficient UASB reactor, researchers have further developed the anaerobic internal circulation (IC) reactor. Due to its high organic load, large treatment capacity, relatively low investment, small footprint, and stable operation, the IC reactor represents the highest level of research in anaerobic reactors at present, and it is worth further research, development, and widespread application. The MIC anaerobic reactor (Multi-Internal Circulation) consists of two reaction chambers connected vertically in series. The first reaction chamber is a high-load chamber, with an inlet water area and an outlet water area at its bottom, while the upper part forms the low-load second reaction chamber. There is a biogas collection hood between the two chambers, and a three-phase separator is located in the upper part of the second reaction chamber; a three-phase separation pack is also present at the top of the reactor. The two reaction chambers and the three-phase separation pack are connected by lift pipes and return pipes. This reactor is integrated by a corrugated plate three-phase separator and a patented anti-clogging device for the return pipe of the internal circulation anaerobic reactor. 2.3 Aerobic treatment process for alcoholic wastewater: The aerobic process involves two stages of aerobic treatment; the first stage uses a trickling bed, while the second stage employs a Carrousel oxidation ditch. The trickling bed utilizes natural ventilation, a spin-type water distributor, and corrugated fillers made of polyvinyl chloride; it can cool wastewater, improve oxygen utilization efficiency, reduce the inlet concentration in the secondary aerobic stage, and minimize foam formation and sludge bulking problems. The Carrousel oxidation ditch consists of an anaerobic section, an aerobic section, and a sedimentation section. Most of the sludge that settles in the sedimentation section is recycled back to the anaerobic section, thereby maintaining a high sludge concentration in that section. After the wastewater enters the anaerobic section of the oxidation ditch, the facultative microorganisms present in the ditch can break down and degrade the difficult-to-decompose long-chain organic molecules in the wastewater, converting them into easily decomposable small molecules. This enhances the biodegradability of the wastewater, facilitating the biochemical reactions in the aerobic section. 2.4 Wastewater Treatment Process and Description The process flow for treating distillers’ grain liquor is shown in Figure 1. Figure 1: Wastewater treatment process diagram. Figure 3: Development and design of the MIC reactor. 3.1 Successful development of the MIC reactor. From 1999 to 2001, I was involved in the “Jiangsu Provincial Environmental Protection Department’s Environmental Protection Science and Technology Development Fund Project – Research on high-load treatment technologies for organic wastewater (study on the application of MIC (Multi-Stage Anaerobic Internal Circulation) reactors at industrial scale).” The MIC reactor developed in this project had a diameter of 8 meters, a height of 23 meters, a total water volume of 1,100 m3, and an effective reaction volume of 800 m3. This MIC reactor is used to treat citric acid wastewater, with a water inflow rate of about 30 m3·h-1 and an inlet COD level of 8,000–12,000 mg·L-1. The commissioning involved processes such as reactor heating, sludge acclimatization, load increase, and stable operation. After the system started operating normally, the organic load in the MIC reactor reached 20 kgCOD·m-3·d-1, the hydraulic retention time was approximately 12 hours, and the COD removal rate exceeded 90%, indicating stable operation of the reactor. In 2001, the Jiangsu Provincial Department of Environmental Protection conducted a technical evaluation of this achievement (Document No. Su Huan Jian Zi 016). It was stated that this achievement \"filled the gap in China regarding third-generation anaerobic reactors for treating high-concentration organic wastewater.\" The research findings indicated that the MIC reactor features a high organic load, a short hydraulic retention time, a small footprint, and strong resistance to shock loads, making it highly valuable for use in the treatment of high-concentration organic wastewater. 3.2 Design of MIC reactors: There are 3 primary MIC reactors in total. The designed influent water quality for these MIC reactors is 30,000–35,000 mgCOD·L-1, with a flow rate of 2000 m3·d-1. The organic load designed for these MIC reactors is 15 kgCOD·m-3·d-1. This paper focuses on the primary MIC reactor (hereinafter referred to as the MIC reactor). The design dimensions of this reactor are as follows: diameter of 15 m, height of 23 m, volume of 4000 m3; it is constructed of carbon steel with anti-corrosion treatment applied internally. Figure 2 shows the structural diagram of the MIC anaerobic reactor. The MIC reactor uses 4 distributor plates for water distribution, which are evenly arranged along the bottom of the reactor at an elevation of 1–1.5 m. This deflector disc requires no external power; it generates a self-contained diffusive swirl, offering a large scattering area and excellent contact mixing effects. The gas collection hoods are at two levels, at elevations of 8–10 m and 19–21 m respectively. 4 separation packages, each containing 2 rising tubes for the mixed liquid and 1 descending tube; the diameter of the rising tubes is φ125mm, while that of the descending tube is φ426mm. The structural diagram of the MIC anaerobic reactor is shown in Figure 2. 4 Startup, Operation, and Performance Analysis of the MIC Reactor 4.1 Inoculation and Startup of the MIC Reactor The sludge used for inoculating the MIC reactor was anaerobic digestion sludge from an urban sewage treatment plant, with an inoculation amount of approximately 50 kg MLSS·m-3. Cooling wastewater was first mixed with the process wastewater (≤1,000 COD mg·L-1, water temperature of 35–39°C) to initiate the reaction and restore the activity of the sludge; the startup period lasted around 15 days. Once the seed sludge has gradually adapted to the characteristics of the wastewater, the organic load in the influent can be increased gradually, with each increase being in the range of 0.5–1.0 kgCOD·m-3·d-1; effluent recirculation is used for acclimatization. As the load increases, the sludge in the reactor gradually changes from a loose state to flocs with good settling properties; the methane-producing activity of the sludge also increases accordingly, leading to a rise in gas production. Loss and elimination of floculent sludge occur, while granular sludge gradually forms and becomes more granularized. The organic load of the incoming water is around 15 kgCOD·m-3·d-1, and the acclimatization period is 3 months. The operation of the MIC reactor during the domestication phase is shown in Figure 3. Figure 3 shows the variations in the organic load in the MIC reactor and the COD level in the effluent over time during the domestication phase. As the MIC reactor was brought online, the organic load of the influent increased from 6.5 kgCOD·m-3·d-1 to 15 kgCOD·m-3·d-1, while the COD level in the effluent rose from 600 mgCOD·L-1 to 1,200 mgCOD·L-1. The COD removal efficiency of the MIC reactor ranged between 85% and 95%. 4.2 Operation of the MIC reactor: During normal operation, process wastewater and aerobic treated water are used as the feedwater for the MIC reactor. The water temperature is maintained at 35–37°C, while the organic load is kept around 15 kgCOD·m-3·d-1. The COD level in the effluent remains stable, with a COD removal efficiency of approximately 88%; the COD concentration in the effluent from the MIC reactor is between 1200–1500 mgCOD·L-1. Water samples from the inlet and outlet are monitored three times a day, with parameters including pH, COD, VFA, temperature, and flow rate. During its operation over more than a year, the MIC reactor was exposed to stresses such as low pH levels, high organic load, and start-up/shutdown cycles. This further tested its capacity to buffer wastewater with low pH values, its ability to handle high and low loads, as well as the effectiveness of its recovery after restart. The condition of the MIC reactor during operation is shown in Figure 4. Figure 4: Changes in the organic load of MIC and the COD removal rate over time during the stable operation phase. 4.3 pH of the MIC reactor: The pH of the MIC reactor is the result of various factors, including the dissolution equilibrium of CO2, H2S, and NH3 between the gas and liquid phases, the acid-base balance within the liquid phase, and the ion dissolution equilibrium between the solid and liquid phases. Alcoholic wastewater has a low pH and a high COD concentration; 1.125 kg of Ca(OH)2 per m3 of process wastewater is added and mixed with the effluent from the aerobic system to serve as the feedwater for the MIC reactor. Thanks to the granulation of sludge, the pH of the effluent from the MIC reactor ranges from 6.5 to 7.2. The graph showing the change in the effluent pH of the MIC reactor with varying influent pH is shown in Figure 5. Figure 5 shows the variation of the effluent pH in the MIC anaerobic reactor as a function of the influent pH. Under normal operation of the MIC reactor, acid-producing bacteria and methanogens maintain an equilibrium with each other, keeping the pH of the digestate within a near-neutral range of 6.5–7.5. 5 Conclusion (1) It is feasible to use a MIC reactor with two stages of anaerobic treatment combined with a process involving two stages of aerobic treatment for the treatment of alcohol wastewater, and the effluent can meet the secondary discharge standards. (2) More than a year of operation has shown that these three primary MIC anaerobic reactors can operate at high load with continuity and stability. Under conditions of an effective load of 15 kgCOD·m-3·d-1 and a temperature of 35–37 °C, the MIC anaerobic reactor can treat high-concentration wastewater from corn alcohol, achieving a COD removal rate of over 88%. (3) In a MIC anaerobic reactor, at low pH and with an adequate amount of sludge inoculated, the anaerobic system can start up rapidly. The MIC anaerobic reactor can maintain good alkalinity after the addition of a small amount of calcium salts. (4) The MIC reactor is a unit within the entire wastewater treatment system. When using MIC, just like with other anaerobic technologies, attention should be paid to the pretreatment stage, the selection and dewatering of sludge after anaerobic treatment, as well as the collection and utilization of biogas. This enables it to be integrated with other units, avoids the tendency to prioritize equipment over proper treatment processes, and helps ensure that wastewater treatment entities recognize the complexity of such treatment. References: Ma Sanjian, Wu Jianhua, Liu Feng, et al. Development and Application of Multi-Stage Internal Circulation (MIC) Anaerobic Reactors. Beijing: China Biogas, 2002, 20(4). Wang Kaijun, Qin Renwei. Treatment of Wastewater from Fermentation Industries. Beijing: Chemical Industry Press, 2000.9: 115-208. Hu Jicui, Zhou Mengjin, Zuo Jian’e, et al. Theory and Technology of Anaerobic Biological Treatment of Wastewater. Beijing: China Architecture & Building Press, 2003(5): 121-127. Author’s profile: Xu Fu (born 1976), male (Mandchu ethnicity), from Chengde, Hebei Province; master’s degree holder, assistant engineer, mainly engaged in work related to water pollution control engineering. Contact number: 13862124159, 0512-68093261; E-mail: epat_xf@163.com; Fax: 0512-68245831. Address: Institute of Environmental Protection and Applied Technology, Suzhou University of Science and Technology, No. 1701 Binhe Road, Suzhou City, Postal Code: 215011. Funded project: High-tech Industrialization Project in Jiangsu Province’s universities (JH01—084). Author’s profile: Xu Fu (born 1976), male (Mandchu ethnicity), from Chengde, Hebei Province; master’s degree holder, mainly engaged in work related to water pollution control engineering. This post was last edited by cdpulin on 2009-3-26 13:34]

Research on the Operation of UASB in Treating Alcohol Wastewater Du Bing, Qi Wenyu, Shen Lixian, Yang Ruizong Abstract: This paper discusses the startup and operation of a UASB reactor with an effective volume of 2700 m3 in treating alcohol wastewater with high suspended solids under high-temperature conditions, as well as the process of particle sludge formation. When the reactor is operating stably, the SS in the influent is above 10,000 mg/L; the volume load can reach 7–12 kg COD/(m3·d), the hydraulic retention time is 2–5 days, the COD removal rate is over 90%, and the COD in the effluent is less than 5,000 mg/L while the SS is less than 2,500 mg/L. 　　Keywords: UASB ； High-temperature anaerobiosis ； Alcoholic wastewater ； Granular sludgementation ； 　alcohol wastewater ； 　Granular sludge: The treatment and utilization of alcohol wastewater have always been a major issue in environmental protection within the alcohol industry. Wastewater contains high levels of organic matter and suspended solids; the COD is generally between 30,000 and 60,000 mg/L, while the SS is between 10,000 and 20,000 mg/L. Currently, feed is usually recycled and processed using traditional anaerobic fermentation techniques. Excessively high suspended solids content is the main factor limiting the use of efficient anaerobic treatment processes. After years of research, the Beijing Institute of Environmental Protection Science has developed a practical technology called \"Upflow Anoxic Sludge Bed (UASB) technology for treating high-concentration organic wastewater.\" This technology has achieved excellent results in the practical application to treat alcohol wastewater at the Jingzi Winery in Shandong Province. This article summarizes the operational results of this treatment system. 1 Quality and quantity of alcoholic wastewater Shandong Jingzhi Winery is a major brewing enterprise in Shandong Province; it produces alcohol from sweet potatoes (15,000 tons per year) and starch from corn (40,000 tons per year). While constructing the starch production facility, the plant carried out comprehensive treatment of alcohol wastewater. 　　High-concentration organic wastewater originates from three workshops: the mash discharged from the alcohol workshop (600 m3/day); after partial filtration to recover feed, 400 m3 of alcohol wastewater is discharged daily ； The grain wine workshop discharges 40 m3 of bottom water from the pool daily ； The starch workshop discharges 750 m3 of pretreated starch wastewater per day. Wastewater mainly contains starch, sugars, organic acids, proteins, cellulose, etc., with a high concentration of organic substances and large variations in that concentration. Table 1 lists the water quality of the wastewater. 2 Wastewater treatment process The wastewater treatment at Jingzhi Winery is divided into two parts: anaerobic treatment of high-concentration organic wastewater, and aerobic as well as physicochemical treatment of low-concentration wastewater. The process flow is shown in Figure 1. For anaerobic treatment, the UASB process is used. The UASB system processes 1,040–1,340 m3 of water per day, with 30 tons of COD and 12 tons of SS of organic matter being treated daily. The anaerobic stage requires a COD removal rate of over 85% in order to facilitate integration with the subsequent aerobic treatment and ensure that the effluent meets the discharge standards. Several notes on the treatment process: (1) Alcohol wastewater contains a large amount of suspended solids. Separation is carried out using a mash filtration tank; the separation time is generally 5 to 7 days. After separation, the water volume is reduced to 75%, and the suspended solids content is decreased by about 50%. The separated solids are used as feed. 　　(2) The temperature of the separated wastewater drops rapidly. To adapt to summer temperatures and improve digestion efficiency, high-temperature fermentation is employed. Steam heating is provided in the regulating tank during winter. 　　(3) Although the pH of the wastewater is low, appropriate recirculation during the initial operation phase can help meet the requirements regarding acidity and alkalinity; once the sludge has matured and the system possesses sufficient buffering capacity, recirculation is no longer necessary. 　　(4) The UASB consists of 10 units in total, with a total volume of 3950 m3 and an effective volume of 2700 m3. 　　(5) The biogas produced by UASB has a low sulfur content, so no desulfurization is required; it can be directly fed into boilers for combustion. 　　(6) The BOD content in the effluent from UASB is very low, generally ranging from 600 to 900 mg/L, with a BOD/COD ratio of less than 0.2. To meet the requirements specified in the **Comprehensive Wastewater Discharge Standards (GB8978-1996)** (COD less than 100 mg/L), the domestic wastewater generated by the entire plant (approximately 3,800 m3/day) is mixed with the anaerobic treatment effluent and then subjected to aerobic treatment as well as physical and chemical treatments. 3 Production and Operation Status 　 Starting from August 1996, trials were conducted on the anaerobic treatment of alcohol wastewater; by January 1997, all such wastewater was fed into the UASB system. The organic load reached 8 kg COD/(m3·d), with a COD removal rate remaining stable at over 90%. The COD level in the effluent was around 3800 mg/L, while the SS level was around 2500 mg/L. In September 1997, both the bottom water from the pond and the starch wastewater were fed into the UASB system, and the aerobic system was also put into operation. After half a year of operation, all the parameters met the required standards, and in June 1999 the project successfully passed the acceptance inspection organized by the Shandong Provincial Environmental Protection Bureau. 　　Production commissioning can be divided into three stages: the sludge acclimatization and cultivation phase, the load increase phase, and the full-load operation phase. The main control conditions and operation status at each stage are as follows. 3.1 Sludge acclimatization period (1) Source of inoculated sludge and acclimatization Phase 1: Activate tanks 4# and 5# among the 10 anaerobic tanks. Since August 1996, high-temperature anaerobic activated sludge has been added in batches to the anaerobic treatment unit at Shandong Changle Winery; the mixed sludge concentration measured at startup was 17 g/L. Since the water quality and fermentation temperature at Jingzhi Winery are similar to those at Changle Winery, and the inoculated anaerobic sludge has high activity, microbial acclimatization was not required, thereby reducing the startup time. After the temperature rose to 40°C, wastewater was fed into tanks #4 and #5 at a volumetric load of 0.1–0.3 kg COD/(m3·d). When the temperature increased to 52°C and the load reached 2 kg COD/(m3·d), the phase of gradually increasing the load began. 　　Phase 2: The anaerobic sludge from pools 4# and 5# was used and distributed to the remaining 8 pools, with some additional anaerobic sludge from Changle Winery added as well. During startup, the sludge concentration in each tank was 10–21 g/L, with most tanks having a concentration of around 20 g/L. 　　(2) Reactor temperature rise and operation Temperature rise: The anaerobic tank’s temperature is increased from 29°C to 52°C, with an increase of 1.5°C per day. 　　Heating method: The direct steam heating method is used to heat the water in the equalization tank, which is then pumped into the anaerobic tank and flows back to the equalization tank, thus creating a heating cycle. Control the water inflow rate at 4–6 m3/h. 　　During the acclimation period, water is added intermittently twice a day, with the load controlled based on concentration and volume. To further increase the load, it is required that the VFA level in the reactor effluent be less than 200 mg/L, the pH be above 7.2, the COD removal rate be over 80%, and gas production be normal. 3.2 Load increase period The load ranges from 2 kgCOD/(m3.d) up to the point when all high-concentration wastewater enters the anaerobic tank [7–12 COD/(m3.d)]. The first phase took 4 months, and the second phase took 3 months; the operation conditions for each load gradient are shown in Table 2. 3.3 Full-load operation period Since May 1997, all the wastewater from the plant has been sent to the wastewater treatment station for treatment. In particular, the addition of water from the bottom of the tanks not only increased the load but also **increased the gas production volume, while the COD removal rate remained unchanged (over 90%). With fluctuations in water quality, the organic load remains consistently above 8 kgCOD/(m3.d). In April 1999, granular sludge appeared at the bottom of the tank; thereafter, the rate of sludge granulation increased steadily. To date, a large amount of such sludge has accumulated, improving the sedimentation properties and stability of the sludge further, and reducing the concentration of suspended solids in the effluent even more. The UASB unit operates more stably. 4 Discussion 4.1 Reactor Stability The UASB reactor possesses a high buffering capacity, with a total alkalinity of 2200–2900 mg/L; as a result, it can withstand high shock loads. During the commissioning phase, there were three instances of such shock loads, with the highest value reaching 12 kg COD/(m3·d), yet these did not have a significant impact on the reactor, and the volatile acids remained stable or increased only slightly. 4.2 Sludge granulation The special design of the feedwater system and the bottom reflector cone, combined with an efficient three-phase separator that ensures selective retention of a large amount of sludge, creates the conditions necessary for the formation of granular sludge. Maintaining continuous operation, gradually increasing the load, and controlling operating conditions as well as the level of volatile acids are also crucial for the development of granular sludge. After operating for about half a year, a large amount of granular sludge appeared at the bottom of the tank; these particles had a diameter of around 1–5 mm, were smooth in shape, and possessed high strength. 4.3 Gas production volume As the organic load increases, the gas production volume increases accordingly, ranging from 7,000 to 10,000 m3 per day, with a gas production rate of 2.6 to 3.7 m3/(m3·d). When bottom water is added to the dosing tank, its gas generation rate increases rapidly due to the organic acids being its main components. 4.4 Fermentation Temperature The fermentation temperature does not need to be strictly controlled at 52°C during operation, but it is important to maintain consistency in temperature. For a period of time, the reactor temperature was maintained between 40 and 50°C, with the treatment efficiency not being significantly affected. 4.5 Reactor Shutdown When production in the workshop is halted or there is a power outage, the reactor cannot be fed with material, causing its temperature to drop; this has an adverse effect on the reactor. However, normal operation can be resumed once the situation is resolved slightly. 5　Main control measures 　Through production and debugging studies, the following main control conditions were identified. 5.1 Control of pH and VFA The variation in pH level is a key parameter for determining the feed rate to the reactor. During startup, the pH of the anaerobic effluent was maintained above 7.0–7.2, while the VFA level in the effluent was kept below 200 mg/L. The pH of the wastewater from the alcohol production plant is generally 4.0, and no alkali is used for adjustment upon feed-in. After the wastewater is mixed with the anaerobic effluent digestate returned from the regulating tank, the pH is generally above 7.0, meeting the requirements for the incoming water. The debugging process showed that during anaerobic fermentation, by properly controlling the inflow and return flow rates of water, it is possible to eliminate the need for adding alkali. During stable operation, the backflow can be reduced or stopped. 5.2 Control of temperature continuity The reactor temperature should be maintained at a certain level of stability, with temperature fluctuations kept within ±2°C per day, in order to ensure efficient and stable operation of the reaction tank and improve the removal rate of organic substances. 5.3 Control of the applied load During the commissioning phase, the organic load is increased gradually by progressively raising the amount of wastewater fed in. 6 Conclusions (1) The upflow anaerobic sludge bed reactor used for treating the alcoholic wastewater from Shandong Jingzhi Winery, after being adjusted and put into operation, achieved the following stable operational parameters: organic load of 7–12 kg COD/(m3·d), and a COD removal rate of 85%–96% ； Inlet SS is greater than 10,000 mg/L, outlet SS is less than 2,500 mg/L, with an average removal rate of 89% ； Influent BOD: 23,585 mg/L; average effluent BOD: 825 mg/L; BOD removal rate: 97% ； The average gas production rate is 2.3 m3/(m3·d). (2) Under conditions of high suspended solids, a properly designed UASB system, with well-controlled operating conditions and continuous operation for a period of time, can also cultivate granular sludge. 　　(3) The maximum concentration of suspended solids (organics) that UASB can tolerate can exceed the generally accepted level of 2–4 g/L; in practice, it can go above 10 g/L for alcohol wastewater, and in such cases, the removal rate of SS can reach over 85%.

Solid-liquid separation – UASB-SBR technology for treating alcohol distillate wastewater: Abstract: This paper discusses the treatment technologies for alcohol distillate wastewater from potato-based distilleries, and proposes a treatment process that utilizes belt filter presses for solid-liquid separation followed by UASB-SBR. An application example from a winery is used to illustrate the engineering design scheme, the debugging process, and the treatment results. Keywords: potato chip distillation; alcohol leachate; solid-liquid separation – UASB-SBR; belt filter press. The alcohol industry is an important basic raw material industry for the national economy. Alcohol is widely used in fields such as chemistry, food, daily chemicals, and medicine and health. China’s annual alcohol production is around 3 million tons, with grains (such as corn and dried potatoes) serving as the main raw materials. Approximately 80% of grain-based alcohol is produced from dried potatoes. The alcohol waste liquor discharged during the distillation step in the alcohol production process is an organic waste liquid with high levels of suspended solids and a high concentration. According to statistics, over 500 kg of organic matter is emitted for every 1 ton of alcohol produced. The annual discharge of wastewater from the alcohol industry nationwide');"> amounts to about 12 million cubic meters. If large amounts of high-concentration organic wastewater are discharged directly without proper treatment, it will cause severe pollution. Resource waste and environmental pollution have become important factors restricting the development of the domestic alcohol industry. 　　Anhui Sizhou Winery is a liquor factory that produces alcohol using dried potatoes as raw material, with an annual output of 5,000 tons of alcohol. During normal production, 250 m3/d of alcohol lees are discharged, with a temperature of 90°C for the lees. The wastewater mainly contains sugars, organic acids, proteins, and cellulose, etc. The concentration of organic substances is very high, with CODCr ranging from 30,000 to 45,000 mg/L and BOD5 ranging from 15,000 to 25,000 mg/L. The sludge liquor is very turbid, with an SS of approximately 40,000 mg/L. The waste liquid is acidic, with a pH of 3–4. Although alcoholic distillers’ grains have high concentrations of pollutants, they are non-toxic and exhibit good biodegradability. This factory is part of the projects for targeted remediation in the Huai River basin. To completely eliminate the severe pollution it causes to the surrounding environment and groundwater resources, the plant has carried out comprehensive utilization of distiller’s grain waste liquid, constructing a treatment facility for high-concentration organic wastewater (distiller’s grain liquid) with a processing capacity of 250 m3/day. Feed in the spent liquor is recovered simultaneously, along with biogas production. 　　The design wastewater quality parameters are: CODCr: 40,000 mg/L ； BOD5: 25000mg/L ； SS: 20,000 mg/L ； pH: 3.5～4. The quality of the water discharged after treatment should meet the Class 1 standards specified in the \"Integrated Wastewater Discharge Standards\" (GB8978-88): CODCr: ＜350mg/L ； BOD5: ＜200mg/L ； SS: ＜200mg/L ； pH: 6–9. 1 Selection of treatment process One of the keys to the comprehensive utilization and advanced treatment of alcohol distillers’ waste liquid is the effective separation of solids from liquids in this waste liquid. Dehydrating potato chip alcohol waste liquid is a very challenging task. In the past, centrifugal dehydrators and box filter presses were used for such dehydration attempts. Due to the high viscosity and small particle size of this waste liquid, it easily clogs the filters of centrifugal dehydrators and the filter cloths of box filter presses, resulting in unsatisfactory outcomes. Therefore, it cannot be applied to the dehydration of potato chip distillers’ grains liquor. 　　The Environmental Protection Institute of the former Ministry of Machinery conducted in-depth research on the dehydration process for alcohol waste liquid, and developed a new type of belt filter press (see Figure 1). The features of the new belt filter press are as follows: ① Ultra-long gravity dewatering zone ； ②Ultra-long inclined wedge area ； ③Compact press area with increasing pressure ； ④Original filter band offset detection method and dual-end correction mechanism ； ⑤A backwashing method with good performance and high efficiency. Figure 1 Working principle of the new type belt filter press: 1. Press; 2. Reactor; 3. Flow meter; 4. Instant dissolver; 5. Chemical dosing pump; 6. Feeding pump; 7. Air compressor; 8. Flushing pump; 9. Conveyor. Results from industrial tests conducted in a brewery showed that the feed alcohol lees had a moisture content of 96%–96.5%, a pH value of 4.0, and a temperature of 70°C. The moisture content of the distillers’ grain filter cake after dehydration is 72%. Using a belt filter press for the dehydration of alcohol distillers’ grains is an attempt and a breakthrough. The key technical aspect lies in devising targeted methods for adjusting the isoelectric point and corresponding flocculation processes, which can increase the recovery rate of distillers’ grains and the removal efficiency of CODCr from the distillers’ grain liquid (74%), thereby having a significant effect on reducing the load associated with the advanced treatment of the effluent. 　　After solid-liquid separation of the wine lees wastewater using a belt filter press, the CODCr level of the filtrate can be reduced by about 50%, and the SS level also decreases significantly, which facilitates the anaerobic and aerobic biological treatment of the wastewater. The subsequent anaerobic process uses an Upflow Anaerobic Sludge Blanket (UASB), while the aerobic process employs a Sequential Batch Reactor (SBR). 2 Introduction to the treatment process The core of this process consists of solid-liquid separation, UASB, and SBR. The distillers’ grain waste liquid passes through a coarse grid and enters a regulation tank where it is cooled and adjusted. Then, a vertical sludge pump is used to transfer this liquid to a sludge concentration tank; the concentrated liquid subsequently goes into a belt filter press for solid-liquid separation. The filter residue can be processed through extrusion and drying to produce feed ready for sale. The filtrate is pumped into anaerobic UASB and aerobic SBR units for treatment, so that the effluent meets discharge standards. The biogas produced by UASB passes through a water-sealed flame arrester before entering the gas storage tank or being sent to the plant’s boiler for direct combustion (see Figure 2). Figure 2 Process flow for treating alcohol waste liquid at Sizhou Winery 3 Design of main treatment structures and equipment 3.1 Regulating sedimentation tank The regulating sedimentation tank is an underground structure with overall dimensions of 10 m in length, 4.5 m in width, and 3.0 m in depth, and a hydraulic retention time of 2.0 hours. A sludge hopper is installed at the bottom of the regulating tank; the inclination angle of this hopper is 50°. A sludge lift pump is placed inside the hopper to lift the settled sludge to the thickening tank. Two anaerobic feed pumps are installed in the shallow area of the regulating tank, one in use and one as a backup. 3.2 UASB Reactor After solid-liquid separation of the distiller’s grain waste liquid, 50% of the CODCr is removed; the CODCr level of the water entering the UASB reactor is 20,000 mg/L, with a flow rate of Q = 225 m3/d. The design load is 7.0 kgCODCr/(m3•d), with a digestion temperature of 35–37°C. For the UASB reactor, D = 11 m, H = 8.0 m, and the effective water depth is H = 7.5 m. The UASB is equipped with a three-phase separator for supplying water and separating sludge and gas, in order to maintain a highly active anaerobic sludge community within the reaction tank and to effectively recover biogas. The CODCr level of the effluent from the UASB is ≤3000 mg/L, while the SS level is ≤1,500 mg/L. Its biogas production is 2,000 m3/day. 3.3 In the SBR reactor, the CODCr level of the influent water is ≤3000 mg/L, and the SS level is ≤1500 mg/L. The sludge load is 0.3 kg COD/(kg MLSS•day), the sludge concentration is 3 g/L, and the effective volume of the SBR reactor is 750 m3. Two circular SBR reactors are installed in accordance with the requirements of the wastewater treatment process. The dimensions of each SBR reactor are: D=11m, H=5.0m, with an effective water depth of 4.5m. 　　Different operating cycles are determined based on the operating patterns and design requirements of the SBR reactor. The drainage is carried out using a grating type drain, with its elevation controlled by a timer to facilitate drainage. 　　The aeration system uses medium-porosity aerators; assuming an oxygen utilization rate of 10% for these aerators and a CODCr removal efficiency of 90% in the aeration tank, the air supply volume should be 10 m3/min. Three SSR100 fans are selected, with two in use and one as a backup. 3.4 Fan Room Three SSR100 centrifugal fans are installed in the fan room, with 2 in use and 1 as a backup. The air volume per unit is 6.73 m3/min, with H=5.0 m. 　　The fan room is equipped with a sound-insulated power distribution room and an operation rest area. The total dimensions of the fan room are: length × width × height = 10m × 5m × 7m. 3.5 Sludge Thickening Tank After the distillers’ grain liquid enters the adjustment sedimentation tank, most of the sludge settles in the sludge hopper; it is then pumped to the sludge thickening tank for thickening, thereby facilitating subsequent mechanical dewatering of the sludge. The sludge thickening tank is of semi-underground reinforced concrete structure, with geometric dimensions of D×H = 5.0m×7.0m. 　　The concentrated sludge is fed into a belt filter press for mechanical dewatering, while the supernatant from the concentration tank is returned to the adjustment tank before being sent to a UASB anaerobic reactor for treatment. 3.6 Sludge Dewatering Machines and Dewatering Rooms The concentrated waste liquid and sludge are pumped using slurry pumps to a pipeline mixer, where they are mixed with polymer flocculants and coagulants. After reacting in a folded-plate flocculation reactor, they are sent to a belt filter press for dewatering. In this design, a belt filter press with a width of 1.5 m is used, having a processing capacity of 13.5 m3 of wet sludge per hour. The filtrate from the dehydrator is returned to the regulation tank and then sent to the UASB for further treatment. The tap water and air used for backwashing the belt filter press are supplied by a centrifugal pump and an air compressor. The dewatered sludge cake (with a moisture content of 80%) has high nutritional value. The chemicals used in this process have been shown through pharmacological tests and feeding trials to be non-toxic and harmless to livestock; therefore, the sludge cake obtained from the belt filter can be used directly as feed. At a cost of 500 yuan per ton of feed (dry matter), and assuming 300 working days per year, the annual revenue would amount to 1.2 million yuan. 　　The sludge dewatering plant consists of a machine room, a power distribution room, and a control room. It is equipped with 1 belt filter press with a bandwidth of 1.5 m, along with auxiliary equipment such as sludge pumps, chemical dissolving tanks, and air compressors. The floor dimensions of the dewatering room are L×B = 12.0 m×5.0 m, with a ceiling height of 5.0 m; the structure is brick-concrete. 4 Operation, commissioning, and performance The commissioning of the plant begins with the anaerobic section and is carried out in three stages: sludge acclimatization period, load increase period, and full-load operation period. Commissioning of the anaerobic section began in October 1997, and by April 1998 all the alcoholic wastewater was fed into the UASB reactor. The organic load reached 8.0 kg CODCr/(m3•d), with a CODCr removal rate remaining stable at over 90%; the CODCr concentration in the effluent was around 2500 mg/L, while the SS concentration was around 1500 mg/L. In March 1998, the aerobic system was also put into operation, and after 3 months of operation, all indicators met the required standards. 　　First stage: Sludge acclimatization period – Anaerobic sludge from the anaerobic treatment system of the Lingbi Winery in a neighboring county is used for inoculation; after inoculation, the sludge concentration in the reactor is approximately 20.0 g/L. Since the water quality and fermentation temperature in the two plants are similar, there is no need to acclimate the sludge, thereby reducing the startup time. The anaerobic tank is raised from 20°C to 37°C, with a temperature increase of 1–2°C per day. A small amount of the high-temperature wastewater from the regulating tank is pumped into the anaerobic tank, while the excess wastewater flows out, thus enabling a heating cycle. Control the water inflow rate at 4–6 m3/h. At the same time, wastewater is added at a volumetric load of 0.1–0.3 kg CODCr/(m3•d). When the temperature rises to 37°C and the load reaches 2 kg CODCr/(m3•d), the stage of increasing the load begins. 　　Second stage: load increase period – On the basis of stable operation of the reaction tank, the load is increased from 2 kgCODCr/(m3•d) to the design load of 7.0 kgCODCr/(m3•d). During the acclimation period, water is added intermittently twice a day, with the load controlled based on concentration and volume. It is required that the volatile fatty acids (VFA) in the effluent from the reaction tank be less than 200 mg/L, the pH be above 7.2, the CODCr removal rate be over 80%, and gas production be normal, before the load can be increased further. The entire commissioning period lasted about 7 months (4 months in the first phase and 3 months in the second phase). Once the UASB reached its designed load in April 1998, the CODCr removal rate remained above 90%. Although water quality fluctuates, the organic load remains consistently above 7.0 kgCODCr/(m3•d). As the organic load increases, the gas production also increases accordingly, with a gas production rate of 2.6–3.7 m3/(m3•d). The commissioning of the SBR aerobic reactor is relatively simple. First, clean water and a small amount of waste liquid are injected into the reactor to start aeration; once sludge has formed, the amount of waste liquid is gradually increased. Full capacity operation was achieved starting in March 1998, with a CODCr removal rate of over 90%, and the effluent quality met the specified discharge standards. 　　From May 19 to 21, 1998, the Anhui Provincial Environmental Monitoring Center conducted tests on the wastewater generated by a wine factory during its production process. The results showed that the average concentrations of CODCr and SS, as well as the pH value, and the amount of wastewater produced per ton of alcohol in the case of the Sizhou Wine Factory, all met the requirements specified in the \"Integrated Wastewater Discharge Standards\" (GB8978－88) for fermentation and brewing industries. References 1 Wang Kaijun. Further discussion on the anaerobic (hydrolysis)-aerobic treatment process. Chinese Journal of Environmental Sciences, 1998, 18(4): 337–340. 2 Du Bing, et al. Research on the operation of UASB in the treatment of alcohol wastewater. China Biogas, 1999, 17(2): 14–17. 3 Zhang Deqing. Discussion on the engineering design for the treatment of waste liquid from potato-based alcohol production. Water Supply and Drainage, 1999, 25(7): 34–36