Study On Treatment Of Rural Domestic Wastewater In Different Smaller Scale Tests Of Constructed Wetlands

Constructed Wetland (CW) can be an economic, cost-effective and ecological technology to the problem of wastewater treatment. It was shown that CW is a low-cost technique suitable for local settlements and remote sites.This study is made up of two parts, aeration in short time for primarily treatment of domestic sewage; CWs technology for treatment domestic sewage.The pretreatment is conducted by hydrolysis acidification and aeration to evaluate the effectiveness of aeration in the performance of reducing the COD concentration load of inflow, the desired value of effluent COD concentration in this part between80mg/L to200mg/L Compare the removal efficiency of the COD and ammonia nitrogen at one hour aeration time and two hours aeration time, We know that the longer aeration time, the better removal efficiency. But the effluent COD concentration reduces to80-200mg/L when aerate it only one hour, so we adopt the pretreatment sewage scheme:after9h hydrolysis acidification and aerate1h, then discharge the clarified wastewater to the CWs.In this paper, six sets of constructed wetland have been discussed:(A) the first vertical wetland combines the first subsurface flow wetland (VW1+SSW1),(B) the second subsurface flow wetland combines the second vertical wetland (SSW2+VW2),(C) the third subsurface flow wetland (SSW3),(D) the fourth subsurface flow wetland (SSW4),(E) the first vertical wetland(VW1),(F) the second vertical wetland (VW2). The substrate of the former three groups are gravel and sand, while the group D is limestone.There are two aspects on the technology of the CWs to deal with waste water. The first objective is to study the performance of the four sets (A, B, C, D) treating domestic wastewater, and the performance involves several tests about COD TN TP BOD5at different hydraulic surface Ioading0.2m3/(m2·d),0.4m3/(m2·d),0.5m3/(m2·d),0.6m3/(m2·d); the second objective is to compare the performance of strengthening denitrification between E and F while the F is added extra bacterium but the E is not. The results of experiments are as follows:the hydraulic loading plays a very important role in the treatment of rural domestic wastewater, and the purifying effects of the four sets CWs are decreased with the increasing of hydraulic loading. When the hydraulic loading is at0.4m3/(m2·d), four sets in better results; the effluent pollution indicators of the two combined constructed wetlands are lower than the two single subsurface flow wetlands. But the indicators of A and B are nearly equal; Group D which has limestone substrate has the best denitrification than the other three sets have, and the effluent is qualified to the standard of "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant"(GB18918-2002) for TN; The comparative study about two groups of vertical flow constructed wetlands E (didn’t add bacterium) and F (adding bacterium) have shown that the set F has raised COD average removal rate and NH4+-N average removal rate by7.5percent and15.6percent.