Performance of Bio-zeolite Constructed Wetland in Dispersed Swine Wastewater Treatment

Abstract

The anaerobically digested effluent of the dispersed swine wastewater was treated by a three-stage bio-zeolite constructed wetland, and the performance of the wetland, the variation of pollutants concentration in effluent and ORP distribution in the bio-zeolite layer were studied. The results showed that COD, N and P in the digested effluent could be efficiently removed by the wetland, and the wetland also had resistance to ammonia impact load. When the hydraulic loading rate was 0.047 m3·(m2·d)-1, COD, NH4+-N and TN (the average mass concentrations in inflow were 477.7, 155.3 and 176.4 mg·L-1) were mainly removed in the district 1 of the wetland, and the average removal rates were 80.6%, 55.3% and 58.1%, respectively. There was obvious enhancement of nitrification in the bio-zeolite, and the major nitrification product was nitrate. The mass concentrations of NO3--N in the district 1, district 2 and district 3 of the wetland were 85.85, 91.06 and 82.41 mg·L-1, respectively. The nitrate produced in bio-zeolite layer of the district 1 could be denitrified by microorganisms in the slag brick layer using the residual organic substances in water as the substrate. TP was mainly removed by adsorption in the slag brick layer, and the role of microbe assimilation was relatively small. The reaeration of the bio-zeolite layer in the three-stage wetland was good. Most of the ORP values remained over 400 mV in the bio-zeolite layer.