Effects of technical parameters on purification of breeding wastewater by earthworm ecofilter

ObjectiveThis paper studied effects of technical parameters such as earthworm adding amount, filter ma-terial adding intensity and filter material adding mode on purification of breeding wastewater by earthworm biofilter, deter-mined the optimal condition for scale purification of breeding wastewater by earthworm biofilter, so as to provide technical support for breeding wastewater purification. MethodEarthworm ecofilter technology was used to purificate breeding wastewater. Total nitrogen(TN), ammonia nitrogen(NH4+-N), nitrate nitrogen(NO3--N), total phosphorus(TP), phosphate (PO43-), chemical oxygen demand(COD), pH value and electrical conductivity(EC) in water were measured. ResultUnder the same amount of earthworms and filter material, removal effects of single layer earthworm ecofilter on TN、NH4+-N、NO3--N and COD was better than those of double layer earthworm ecofilter; but the removal effects of double layer earthworm ecofilter on PO43- was better. When the material adding intensity was 2.25-4.50 m3/m2·d, the removal effects on NH4+-N,TN,TP and COD in earthworm ecofilter was the best, but there was no obvious influence on NO3--N content, pH value and EC value. When earthworm adding amount was 0.5 kg/box, the average removal rates of TN,NO3--N,NH4+-N,TP, PO43- and COD for inlet water were lower than those in treatment with 1.0-2.0 kg/box earthworm. Excess addition of earth-worm could lead to increase of EC value in outlet water. ConclusionEarthworm ecofilter can continue to remove nitrogen, phosphorus, carbon and other pollutants efficiently and steadily in breeding wastewater. Considering comprehensive cost and efficiency, the suggested technical parameters are as follows:sigle layer material addition with intensity of 4.50 m3/m2·d, and earthworm addition is 1.0 kg/box.