Pollutants removal and simulation model of combined membrane process for wastewater treatment and reuse in submarine cabin for long voyage

A laboratory scale test was conducted in a combined membrane process （CMP） with a capacity of 2.91 m3/d for 240 d to treat the mixed wastewater of humidity condensate, hygiene wastewater and urine in submarine cabin during prolonged voyage. Removal performance of chemical oxygen demand （COD）, ammonia nitrogen （NH4^＋-N）, turbidity and anionic surfactants （LAS） was investigated under different conditions. It was observed that the effluent COD, NH4^＋-N, turbidity and LAS flocculated in ranges of 0.19-0.85 mg/L, 0.03-0.18 mg/L, 0.0-0.15 NTU and 0.0-0.05 mg/L, respectively in spite of considerable fluctuation in corresponding influent of 2120-5350 mg/L, 79.5-129.3 mg/L, 110-181.1NTU and 4.9-5.4 mg/L. The effluent quality of the CMP could meet the requirements of mechanical water and hygiene water according to the class I water quality standards in China （GB3838-2002）. The removal rates of COD, NH4^＋-N, turbidity and LAS removed in the MBR were more than 90%, which indicated that biodegradation is indispensable and plays a major role in the wastewater treatment and reuse. A model, built on the back propagation neural network （BPNN） theory, was developed for the simulation of CMP and produced high reliability. The average error of COD and NH4^＋-N was 5.14% and 6.20%, respectively, and the root mean squared error of turbidity and LAS was 2.76% and 1.41%, respectively. The results indicated that the model well fitted the laboratory data, and was able to simulate the removal of COD, NH4^＋-N, turbidity and LAS. It also suggested that the model proposed could reflect and manage the operation of CMP for the treatment of the mixed wastewaters in submarine.

Comprehensive Analysis of 9-year Running Data of A^2/O-MBR in Xi an Siyuan University

Since September 2011,A 2/O-MBR wastewater treatment plant in Xi'an Siyuan University has been successfully running without replacing any of membrane modules.A total of 6.661 million m^3 of campus wastewater has been treated,and 4.405 million m^3 of water reaching the national urban miscellaneous water standard has been reclaimed and reused.A total of 25 km pipeline,5 pits,scenery fountains,lakes,and 12 pump stations have been constructed for flushing toilets,irrigating green grass lawn and afforest,and cleaning hardened pavement.The design and construction of 5 pits,scenery fountains,and lakes are important to meet the national urban miscellaneous water standard under occasional phosphorus and/or nitrogen exceed concentration.The unit water cost is 4.19 yuan/m^3,including membrane modules depreciation and amortization.After the A 2/O-MBR system passes the membrane modules depreciation and amortization period,the unit water cost is 2.82 yuan/m^3.The water productivity of the membrane stack rises first at the beginning of operation,reaches the maximum value,and then decreases.The average annual transmembrane pressure difference increases by 1.12 kPa.The average VMD of industrial permeability decreases annually by 0.45 m^3.