Technical options for treating alcoholic wastewater to meet Class A standards

Artificial wetlands are good, but they require a large amount of space and are highly affected by temperature. How to address this? It is more appropriate to use membrane treatment or BAF. **The standards set are too strict; hardly any company can meet them. It’s better not to release it if the company can’t do it. Those who set the standards don’t even know what they’re doing; whose opinions were consulted?

Artificial wetlands require large areas of land that are not in use, and this is practically unfeasible given the current shortage of land. Currently, the alcohol industry achieves first-class emission standards by adopting clean production processes combined with anaerobic and aerobic treatment methods. The alcohol treatment projects I have worked on use the UASB+A/O process to achieve the required standards, and the biogas produced in the anaerobic process can be reused in gas boilers and similar devices, thereby enabling the recycling of waste resources. The prerequisite is that alcohol production enterprises must adopt clean production processes!

It’s not impossible to meet the standards, but the high operating costs are generally beyond what ordinary companies can afford – and that’s the key issue.

Economy is the ultimate goal of technological progress. I personally believe that artificial wetlands constitute a reasonable technology for final treatment; developed countries have already made it an enforceable standard, while in our country we currently only advocate for its use – although experiments have already been conducted in many areas across the nation. I believe that this technology will soon become a technology that drives progress.

Considering cost-effectiveness, it’s of course a constructed wetland； However, the huge land area is something that a business cannot afford; simpler measures need to be adopted!

Wetland treatment can be employed only when the pre-treatment is of good quality; for example, it is feasible if the effluent from the pre-treatment has a quality level of around 100-200. If the pollution is still severe, using wetland treatment is equivalent to polluting the environment. Alcoholic wastewater is one of the types of wastewater that is difficult to treat due to its high concentration of pollutants, and its treatment costs are high. Using wetland treatment methods is somewhat wasteful of land and not very practical; what LZ suggested seems to be a case study rather than something that can be applied on a broader scale.

1 Sources of wastewater and water quality and quantity: A alcohol factory in Henan produces alcohol using corn as raw material, with an annual output of 10,000 tons of alcohol. The wet process is employed for alcohol production instead of the traditional whole-grain method; in this process, corn is soaked and its germ is separated, after which starch slurry is used to produce alcohol. Alcohol is produced by separating the germ, which on one hand reduces the levels of fats and proteins in wastewater, thereby lowering the degree of water pollution and the difficulty of wastewater treatment; on the other hand, the separated germ can be used to produce corn oil, generating significant economic benefits. The alcohol plant generates 400 m3 of alcoholic wastewater per day. This wastewater originates mainly from soaking wastewater, the residue left after fermentation and distillation, and water used for cleaning workshop equipment. The quality parameters of this wastewater and the corresponding discharge standards are shown in Table 1. 2 Wastewater treatment process Process flow Alcohol wastewater is an acidic, high-concentration organic wastewater rich in nutrients, making it difficult to treat. Therefore, wastewater treatment should be approached from the perspectives of clean production and comprehensive resource utilization in order to reduce the difficulty of treating wastewater. In addition to tapping potential from the alcohol production process by replacing the traditional whole-grain method with a wet-process method, which reduces the levels of fats and proteins in wastewater and thus lowers the difficulty of wastewater treatment, it is also necessary to choose wastewater treatment processes that can recover useful components from the wastewater, offer good treatment results, and operate stably. Based on engineering experience as well as the results of pilot and scale-up tests, the alcohol wastewater treatment process shown in Figure 1 was determined. Operation results: After more than three months of debugging, this wastewater treatment system entered normal operation. The monitoring results over consecutive periods after normal operation are shown in Table 2. As can be seen from Table 2, the system operates reliably, achieves good treatment results, maintains stable water quality that meets the standards, and the wastewater treated at a rate of 200 m3/d is reused for workshop production purposes, plant landscaping, and other general purposes. 3 Benefits Analysis of Comprehensive Utilization of Wastewater 3.1 Benefits Analysis of Corn Oil Production In traditional corn alcohol production, the whole-grain method is generally used: corn kernels are fed directly into the process, where they undergo crushing, steaming, saccharification, and fermentation to produce alcohol. The fats and proteins contained in corn are not separated and utilized, and all of them end up as alcohol waste liquid. This not only leads to waste of resources but also increases water pollution and makes wastewater treatment more difficult. From the perspective of clean production and comprehensive resource utilization, this project adopts a wet-process method: corn is soaked to separate the germ, which is then used to produce alcohol via starch slurry; the separated germ can be used to produce corn oil, thereby reducing the difficulty of wastewater treatment. Corn oil is rich in linoleic acid and vitamin E; it possesses good frying properties and antioxidant capabilities. It is a plant-based oil that is easily absorbed by the human body and is highly nutritious. Additionally, corn oil has functions such as reducing cholesterol, preventing cardiovascular diseases, and slowing down aging, which has earned it widespread attention in the market. Due to the low production volume of corn oil in our country, its demand is high; refined corn salad oil has become one of the highest-quality edible oils, and its price is also higher than that of other oils. At the current market price of 8,800 yuan per ton for corn oil, if 10,000 tons of alcohol are produced annually, 30,000 tons of corn will be consumed, resulting in 380 tons of finished corn oil. The annual economic value generated will be 3.344 million yuan. In addition, the oil cakes produced during the corn oil production process can also be sold, yielding significant economic benefits. 3.2 Analysis of the economic benefits of feed production Alcohol wastewater contains a large amount of nutrients, and its nutritional value is roughly comparable to that of soybeans; it therefore has high value for recycling. In addition to being used to produce soy sauce, vinegar, and edible mushrooms, it is primarily utilized in the production of protein-based feeds. Alcoholic wastewater is processed through solid-liquid separation, dehydration, and drying to produce high-protein feed. A company with an annual alcohol production capacity of 10,000 tons can produce 6,000 tons of high-protein feed per year. At a market price of 900 yuan per ton for such feed, and with costs (for raw materials, auxiliary materials, microorganisms, labor, electricity, and depreciation) amounting to 400 yuan per ton, a profit of 500 yuan can be earned per ton of feed, resulting in an annual profit of 3 million yuan. At the same time, after solid-liquid separation to recover the feed, 70% of COD and 80% of SS in the wastewater were reduced. 3.3 Benefit analysis of biogas utilization: Alcohol wastewater is a type of high-concentration organic wastewater. Treating it through anaerobic digestion using a UASB reactor not only significantly reduces the COD level of the wastewater but also generates large amounts of biogas that can be reused. Biogas is a good clean fuel. The gas production rate of UASB reactors is generally 0.5 m3/kg COD, allowing for the generation of 2800 m3 of biogas per day. Typically, the heat value of 1000 m3 of biogas is equivalent to that of 1 ton of coal; with the price of coal at 260 yuan per ton, the economic benefit resulting from biogas recovery amounts to 728 yuan per day. 3.4 Analysis of the benefits of recycled water: After treatment, 200 m³/day of wastewater from this alcohol plant is reused as process water in the workshops, as well as for plant landscaping and other miscellaneous purposes. The current industrial water price in Zhengzhou is 10.2 yuan per m3. Recycled water costs 50% of the tap water price, resulting in a daily cost savings of 1,020 yuan. 4 Conclusion In view of the characteristics of alcohol wastewater, such as its high nutrient content, high organic load, and difficulty in treatment, an alcohol factory in Zhengzhou adopted a treatment process that combines comprehensive resource recovery. In other words, while treating alcoholic wastewater, its useful components are recovered, which not only saves resources and generates significant economic benefits but also reduces the difficulty of wastewater treatment, ensuring that the treated water meets regulatory standards before being discharged. Based on the operational performance, it can be seen that this process features a rational design, stable and reliable operation, high removal efficiency, good water quality of the effluent, significant economic benefits, as well as good prospects for application and promotion. This post was last edited by johncom on 2009-4-12 08:43]