Research On Coagulation-IC Reactor Process In The Treatment Of Soybean Protein Wastewater

soybean protein wastewater is a kind of concentrated organic wastewater, which is difficult to be disposed of due to large amount of protein, carbohydrates and other organic matters. With rapid development of soy protein processing industry, pollution caused by soybean protein wastewater is getting more and more attention.Based on comprehensive analysis of numerous literatures, coagulation-Internal Circulation(IC) process was adopted to treat soybean protein wastewater treatment. Coagulation experiment was performed in lab-scale. Al2(SO4)3, FeCl3, PAC, PFS, TiCl4and flocculant synthetized by paper mill sludge (PSF) were utilized as coagulants/flocculants for pretreatment of soybean protein wastewater. The application and performance of PDMDAAC, PAM and enteromorpha as coagulant aids were also examined in this research. Mechanism of coagulation were investigated. IC anaerobic biological treatment was studied in pilot test. During the process, water quality indexes, including organic load, pH, temperature, ammonia nitrogen and removal rate of CODCr-were monitored regularly. The main conclusions were summarized as follows:1. Coagulation pretreatment could effectively remove CODCr, total nitrogen, total phosphorus and other pollutants in soybean protein wastewater, and reduce the load of the follow-up biological treatment unit.2. It showed that optimal coagulation performance was achieved by PAC-PAM at dosages of0.3g/L of PAC and10mg/L of PAM, after comprehensive analysis and research of the treatment effect, economical and practical factors on all kinds of coagulants/coagulants and coagulant aid. About21%of CODCr,21%of the total nitrogen and60%of total phosphorus in wastewater were removed by PAC-PAM.3. IC anaerobic reactor was started successfully, after around six months of pilot test.The organic load was9.5kgCODCr/(m3·d) and CODCr of effluent was below1000mg/L, while the removal rate reached90%. The other water quality indexes, such as pH, temperature, volatile fatty acid (VFA) also showed the system worked well.4. IC anaerobic reactor had strong resistant capacity against organic load. It still quickly restored in the case of facing an organic loading shock and a temperature drop, during the process.5. Large amounts of well performing granular sludge were produced by inoculating the reactor with floc sludge from municipal sewage treatment plant.Particle size of granular sludge was about0.5to3mm, granular structure was compact and there were a vast array of microbes.6. An external circulation was utilized in the process, which improved the buffer capacity of the reactor. Raw water ran into the reactor without adjusting the pH, in the late run of IC. The external and internal circulation could ensure the appropriate operating conditions in the reactor, which reduced the overall operating costs.