Study On Characters Of A Small-scale Multifunction Household Sewage Purifying-tank

In the last thirty years, more and more household sewage has been discharged to the environment with the living standard becoming better and better especially the tap water engineering carried out in the vast rural areas. However, the municipal wastewater plants cannot be operated in the suburbs, villages and towns, and scenic spots because of the expensive sewage pipe system and the lack of government finance. So the small sewage treatment devices which have characters of high treatment efficiency and low cost are suitable to these dispersed areas. These devices are a complementation for household sewage system in the town, constructing a complete system for household sewage in China.Actual sewage is used in the experiment of investigating a small small-scale purifying-tank with two anaerobic, one aerobic bio-filter to improve the sewage treatment efficiency and reduce the cost invented by the author's team.The influence of domestic sewage treatment in the different zones is investigated with the small-sized purifying-tank with different aeration rates. It is found that the aeration rate has a great relation to the removal efficiency of sewage. The COD_Cr, BOD₅, NH₃-N and turbidity of the effluent are 46 mg/L,9.6 mg/L,23.8 mg/L and 11.2 NTU respectively with the best aeration rate of 3.28 m³/(m³Â·h) and influent at 15 L/d, which is up to the national discharge standard. While the influent is increased to 20 L/d, the effluent also reaches the national discharge standard, so the purifying-tank has a good shock-resistance with the best aeration.The influence of recirculation flow on domestic sewage treatment in different zones of the Purifying-tank was investigated through an experiment of circulating different volumes of sewage from settling zone to the anaerobic zone at the best aeration rate of 3.28 m³/(m³Â·h). It is found that the removal effect get better with a low aeration rate than a normal aeration rate. The COD_Cr, BOD₅, NH₃-N, NO₃^--N and TN of the effluent are 37 mg/L,7.8 mg/L,4.3 mg/L,1.4 mg/L and 10.3 mg/L respectively with the circulating at 30 L/d, which come up to the national first-class discharge standard. The biofilms in the two anaerobic zones grow well and the efficiency of denitrification is high, and simultaneous nitrification and denitrification is found in the aerobic zone.