| This study investigate the engineering design and operation control technology for a walnut milk production enterprise aimed to resolve the problems of high concentrations of suspended solids, grease, and organics in wastewater. The study was based on the pretreatment experiments, and the research results are as follows:1)The chemical coagulation process was applied in the pretreatment experiments of the walnut milk production wastewater. The optimal coagulant was determined to poly aluminium chloride(PAC). The optimal pH was 5.5 and the dosage was 750 mg/L. Under these conditions, the influent and effluent COD were 5800~6200 mg/L and 3300~3600 mg/L, respectively. the influent and effluent SS were 4300~4600 mg/L and 640~690 mg/L, respectively. As a result, the removal rate of COD can reach 43%, the removal rate of SS can reach 86%.2)Considering the wastewater characteristics and the results of pretreatment experiments, "grid+neutralization+flotation+Anaerobic+A/O" was used as the sewage processing technology for the walnut milk production company. In addition, we developed a wastewater treatment program, carried out the wastewater treatment process design.3)After these wastewater treatment facilities was build and 90 days trial operation, the whole system runs stability. The influent COD and SS were 5690~6580 mg/L and 4292~4787 mg/L, respectively. And the effluent COD and SS were 92~149 mg/L and 102~150 mg/L, respectively. The removal rates of COD and SS can reach 98% and 97%, respectively. Thus, the effluent quality meets the Secondary Standard in table 4 of the national "Integrated Wastewater Discharging Standard"(GB8978-1996).4)The construction scale for the operation was 2400 m3/d with an occupied area of 3325 m2. The total investments of the project were RMB 9.65 million. Annual running cost was 2.6467 million / a.The Running costs per unit was 3.30 yuan/ton of water. Benefits from biogas was RMB 1.914 million/a. The sewage processing station costs RMB 732,700. |
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