Treatment of wastewater from biodiesel production

Regulation tank + air flotation system + catalytic oxidation tower + neutralization tank + biological sulfurization bed + sedimentation

Here is a brief description of the design: 1 Process Design 1.1 Physicochemical pretreatment tests for wastewater. Due to the high concentration of organic matter in the wastewater, it is not possible to achieve the desired results through biological treatment alone. Therefore, prior to determining the process for wastewater treatment upgrades, numerous pretreatment tests were carried out. Orthogonal experiments were used to identify the optimal pretreatment process and its parameters, with the results shown in Table 3-1. Table 3-1 Process Parameters and CODCr Removal Efficiency
Process Parameter | Influent CODCr (mg/L) | Effluent CODCr (mg/L) | CODCr Removal Rate
-----------------|----------------------|----------------------|---------------------
Micro-electrolysis and flocculation filtration | 1.5 hours of micro-electrolysis, PAC at 700 PPM, FeCl3 at 2000 PPM, PAM at 20 PPM | 66,400 | 30,200 | 54.4%
1.2 Selected process flow and analysis
Figure 3-1 Process flow diagram
Since the oil content in wastewater accounts for about 18–20% of the COD value, removing this oil through oil separation can reduce the COD level of the wastewater to around 53,000 mg/L, thereby ensuring the proper operation of the micro-electrolysis cells. However, due to time constraints, it was not possible to modify these cells quickly; only simple adjustments were made to improve their oil separation efficiency, resulting in an effluent COD level of 59,800 mg/L. According to calculations, within a reaction time of around 1.5 hours, the microelectrolysis cell and the air flotation system can achieve a COD removal rate of 54.5% for wastewater; in other words, the COD value of the wastewater can be reduced from 59,800 mg/L to around 27,210 mg/L. When domestic sewage is added, the COD level can be lowered to around 19,170 mg/L. However, considering that the operating conditions in actual production are not ideal and thus the pretreatment efficiency decreases, the COD level of the water fed into the UASB reactor is set at 20,000 mg/L. Due to the good biodegradability of this wastewater, as long as the UASB reactor and the activated sludge tank are properly tuned, the effluent after sedimentation can meet the third-level discharge standards. 1.3 Expected treatment effects of various units in the process Table 3-2: Summary of expected treatment effects for each unit in the process Structure name CODCr Oil separation and sedimentation tank Inflow (mg/l) Outflow (mg/l) Removal rate % Oil separation 66,400 53,120 20 Micro-electrolysis tank 53,120 37,184 30 Air flotation tank 37,184 18,592 50 UASB reactor 18,592 4,000 78 SBR tank 2,800 (after dilution with domestic wastewater) 400 86

Since the flowchart cannot be updated, here is another description of the design for one of the main structures: 1. Oil separation and sedimentation tank – Given the high oil content in biodiesel wastewater, removing this oil using an oil separation tank can help reduce COD by about 20%, thereby ensuring the proper operation of the microelectrolysis cell. At the same time, this pool serves a purpose of initial sedimentation. By modifying the company’s existing oil separator tank, baffles were added in front of the tank to improve oil separation efficiency. Dimensions: 9800×4000×3000 mm3. Equipment: 1 PGL-1 type slag scraper, 2 micro-electrolysis cells. When wastewater enters the micro-electrolysis device, a direct current electric field is generated; under the force of this electric field, reactions such as electrode deposition, electrocoagulation, and electrochemical oxidation-reduction take place, resulting in an effective purification effect on high-concentration organic wastewater. The microelectrolysis method features low investment, low operating costs, and simple operation. The designed treatment capacity for production wastewater is 70 m3/d. Dimension specifications: Made of Q235 steel with a fiberglass-reinforced plastic lining for corrosion protection; residence time is 90 minutes, effective volume is 10.5 m3, the flow rate of the empty tank is 0.77 m/h, and the external dimensions of the micro-electrolysis tank are Ф2400×5050 mm. Supporting equipment: 1 ISW150-250(I) backflush pump, 1 FS40-32-125 regenerating acid pump, as well as acid tanks, aeration pipes, etc. 3 Neutralization tank: Since the production wastewater is highly acidic, lime must be added for neutralization in order to ensure the proper operation of the subsequent anaerobic processes. Perforated pipes are evenly arranged for aeration and mixing. The existing idle pool is renovated and equipped with a chemical dosing system. Dimensions: 3500×3820×4000 mm3. Supporting equipment: one set of lime milk dissolving and dosing system, one pH meter. 4. Air flotation unit: The water exiting the micro-electrolysis tank contains a large amount of suspended solids and colloidal organic matter. The pH value of the wastewater rises to around 5, which facilitates the formation of new types of iron hydroxide that have better flocculation properties. After adding coagulants to carry out the flocculation reaction, the mixture is separated into solid and liquid phases using an air flotation unit for removal. The reflux ratio for the pressure dissolved air flotation unit is set at 40%, and the total treatment capacity of the system is 2.91×(1+0.4) = 4.07 m3/h. ☆ Air flotation unit: Made of Q235 steel with a fiberglass-reinforced plastic lining for corrosion protection; the diameter of the separation chamber is 1.2 m, the total height of the air flotation tank is 1.78 m, the hydraulic retention time is 20 minutes, the hydraulic load on the surface of the separation chamber is 5.0 m3/(m2·h), and the upward flow velocity in the contact chamber is 10 mm/s. It includes the device body, a standard diameter of Dd=200mm, one TR-2 type pressure dissolved air tank, a JX-1 type planetary slag scraper, and a dissolved air release system, among other components. The designed dissolved air operating pressure is 0.35 MPa, with gas release achieved using uniformly distributed TS-Ⅱ type dissolved air release devices. ☆ Associated dissolved air pump ISW40-200A, 1 unit, flow rate 5.9 m3/h, head 44 m, power 3 kW ； One air compressor is configured, model: PX0260, displacement 0.09 m3/min, pressure 8 kg/cm2, power 0.37 kW ； It is equipped with FeCl3 dosing tanks, PAC dosing tanks, PAM dosing tanks, and sludge tanks, among others. 5 UASB reactors: UASB, or Upflow Anaerobic Sludge Bed, combines biological reaction with sedimentation; it is a compact and efficient anaerobic reactor. It has a high biomass in its sludge bed and a high volume load rate; moreover, the hydraulic retention time of wastewater in the reactor is short, so the required tank volume is **reduced**. The equipment is simple to operate; there is no need for a sedimentation tank or sludge return system, no filling material is required, and no mechanical stirring device needs to be installed in the reaction area. Its cost is relatively low, it is easy to manage, and there is no risk of clogging. The existing UASB tank was modified by adding a recirculation system (to increase the internal recirculation flow) and a jet drainage system, in order to address the issues of uneven water distribution and low upward flow velocity. And add 1 submersible pump to discharge excess sludge. Dimensions: 9800×9600×8200 mm3. Equipment: 1 QW10-10 submersible sewage pump; 6 SBR tanks, which were converted from existing aerobic activated sludge reactors – the original tanks were divided into two sections in the middle, with domestic sewage being introduced into them. Two additional decanters were added, and the aeration system at the bottom was rearranged. Size of a single tank: 5200×5200×4500 mm3. Associated equipment: 2 BSL100 type rod-type swivel decanters; 2 H4560 type high-pressure Roots blowers in the blower room (1 in use and 1 as backup); 2 QW10-10 submersible sewage pumps. 7. Aerated biological filter: This system is created by modifying an existing secondary sedimentation tank; an aeration system is added at the bottom, the angle of the sludge hopper at the bottom of the original secondary sedimentation tank is adjusted, and additional components such as a central guide tube and a water collection weir are installed. Aeration is carried out for further oxidation when the water quality of the SBR tank effluent does not meet the requirements. Dimensions: 3500×3000×4000 mm3. 8 physicochemical tanks – These are created by modifying existing physicochemical tanks, with chemical dosing tanks added for the addition of H2O2 and FeCl2. When the water quality from the previous steps does not meet the requirements, this tank is used to add chemicals for further oxidation. Dimensions: 3500×3000×4000 mm3. 9 Clarification tanks are used for final clarification and water storage; return pipes are also provided to the tanks where chemicals need to be dissolved, in order to supply dissolved chemical water and backwash water. And the quality of the water discharged can also be observed. Dimensions: 3500×3000×4000 mm3. Equipment: Two 80JYWQ43-13-3 lift pumps are installed at the bottom of the tank; the number of pumps to be activated can be adjusted according to needs. 10 Sludge thickening tank/sludge dewatering system: Dimensions of the sludge thickening tank: 3.00×3.00×3.00. Equipment: Screw pumps ZW25-8-15, with a power of 2.2 KW each; two pumps are used, one in operation and one as a backup. Sludge dewatering system: Pressure filters of type BAJBMJ60/650 are used, with a filtration area of 30. The size of the filter plates (outside dimensions) is 800×800. Filtration pressure: ≤0.6 MPa. Motor power: 3 KW. Technical features: (1) A mechanism designed to facilitate the removal of the filter plates. (2) Mechanical arms are used to automatically pull the filter plates for automatic unloading. (3) Fully automated control via microcomputer, enabling complete automation of the entire operation process. (4) Compression function: Compressed air is used to compress the rubber elements and further reduce the moisture content of the filter cake. (5) Automatic liquid collection tray: Liquid can be collected and discharged centrally, and the tray can automatically retract and return to its original position. 11 Equipment rooms: Blower room: 2.30×5.20×3.00 m. Sludge dewatering room: 5.20×4.00×3.00 m

May I ask the moderator, how much is the total investment? What is the daily processing capacity in tons? Could you leave a phone number or email address? Can we work together? My email is fangyiqing007@sohu.com

Moderator, I was wondering if there are any design companies in this field? If so, could you please recommend some? Our company hopes to cooperate

4# cdpulin, could you please provide a contact method?

7# I really care about you. Email: cdpulin@163.com. We can communicate more.

If sulfuric acid is used as a catalyst, the wastewater discharged contains 1% sulfuric acid, 4% glycerin, and about 1% hydrogen peroxide. I am working on a design for a manufacturer: first, heat and decompose hydrogen peroxide under acidic conditions ； The hot wastewater enters the pseudo-multieffect membrane evaporation unit for concentration by a factor of 6–8 ； Then separate sulfuric acid using solid-phase extraction ； The dilute glycerol aqueous solution is distilled to obtain a high-concentration crude product ； Dilute sulfuric acid was further evaporated and concentrated to 40% using a pseudo-multi-effect membrane. Dilute sulfuric acid is either sold or concentrated to over 95% for reuse. With this design, near-zero emissions are essentially achieved.