Study On Optimization Of Biofilter Material And Degradational Performance Of Pollutants In Wastewater Land Treatment

Wastewater land treatment system is a natural purification technology which uses an ecosystem composed by Soil-Microorganism-Plant to purify pollutants and improve effluent quality. The pollutant removal mechanism of wastewater land treatment includes decomposition of microorganism, absorption of vegetation and physiochemical effect of substrates. The wastewater land treatment has the following advantages: low construction investment and operating costs, simple management, stable operating, better removal efficiency, great compatibility to loading changing, salient profit of ecological surroundings and effluent reusing, etc. It's suitable for small-scale sewage treatment, such as towns and villages.Biofilter material is an important part of the wastewater land treatment system, and it plays a vital role in the purification process of land treatment system. Selection of a biofilter material with low-cost and better removal efficiency strengthens the faculty of land treatment.There are five biofilter materials: bricks, concrete block, cinder, bio-ceramic and detritus which are selected for experiments and study. The results have showed that the cinder has the highest COD_Cr removal efficiency, the average removal efficiency is 54.28%. The following are bio-ceramic, detritus, bricks and concrete blocks on the removal effect of COD_Cr. And the cinder has the highest BOD₅ removal efficiency, the average removal efficiency is 84.82%. The following are bio-ceramic, detritus, concrete blocks and bricks on the removal effect of BOD₅. And the cinder also has the highest TN removal efficiency, and average removal efficiency is 29.02%. The next are concrete blocks, bio-ceramic, bricks, detritus on the removal effect of TN. The concrete blocks have the highest TP removal efficiency, and average removal efficiency is 56.96%. The next are bio-ceramic, cinder, bricks, detritus. Giving priority to COD_Cr and BOD₅ removal effect, cinder has the highest pollutant removal efficiency of the five biofilter materials, and the next are bio-ceramic, detritus, concrete blocks and bricks. Cinder is an economic and efficient bio-filter material, but now most boilers use fluidized bed type, after coal burning only ash left, no cinder, which makes the practical application of cinder being limited. The removal capacity of Bio-ceramic is also better, but its cost is higher than others. The government should depend on economic situation to decide which is used. The cost of detritus is low, and it has higher COD_Cr and BOD₅ removal efficiency, but TN and TP removal efficiency is lower. Concrete blocks have high TN and TP removal efficiency, especially phosphorus removal. However, breaking concrete is too expensive, so it is not economic for land treatment. Bricks have the worst pollutant removal efficiency, and it is not suggested for use.This study can provide a number of operating parameters for wastewater land treatment, and it has a certain practical significance for the treatment of municipal sewage.