Characteristic Of Dispersed Swine Wastewater Treatment With Three-stage Bio-zeolite Enhanced Nitrification Constructed Wetland

As dispersed swine wastewater contains high concentrations of organic matter, nitrogen and phosphorus, it has no obvious removal effect of nitrogen and phosphorus using simple biogas anaerobic treatment. Biological-ecological process provides an economical and feasible route for the dispersed and small scale farming sewage. Artificial wetland is an ecological process that commonly used, but it has significant defects in nitrogen removal ability. Biozeolite can realize ammonia adsorption and regeneration in situ, and remove the ammonia sustainably. Based on the previous studies, a three-stage enhanced nitrification biozeolite artificial wetland was constructed to study the operating performance of the wetland before and after the startup phase, the variation of pollutants concentration overtime in effluent, the variation of pollutants concentration along the brick slag layer, impact of load raised and low temperature and ORP distribution in the biozeolite layer. The processes of nitrogen and phosphorus removing and transforming in the wetland were studied and microbial community structure were analysed with 16 S r RNA sequence. The conclusions of this research were as follows:1. The influent of three stage constructed wetland was the effluent of disperesed swine wastewater after source separation and ABR treatment, while the inffluent concentrations of COD was 350⁷80mg/L, NH₄⁺-N was 75³70 mg/L,TP was 3⁴8mg/L,and the hydraulic loading was 0.047 m3/?m2·d?. COD and NH₄⁺-N in the flushing water were mainly removed in district 1 of the wetland, and the remove rate of COD and NH₄⁺-N in district 2 and district 3 were lower. During the running period of constructed wetlands, the influent concentration of COD and NH₄⁺-N fluctuated greatly. At the situation of higher load of NH₄⁺-N or unfavorable environmental conditions, the three-stage biozeolite artificial wetland can adsorb NH₄⁺-N firstly, and then slowly regenerate over time and release the adsorption sites of NH₄⁺-N to ensure the water quality of wetland system effluent. It showed that the system had a strong capacity to resist the shock load of influent.2. The three-stage wetland system reoxygened by the tidal flow operation mode, adding reinforced oxygen pipe to reoygenation in the district 1 of the wetland, and the reaeration effect of biozeolite layer were preferable. Most of the ORP value remained over 400 m V. COD and ammonia nitrogen removal effect were obvious, and the average removal rate of COD was 85.5%. TN removal mainly depended on the adsorption of zeolite to ammonia nitrogen and nitrification/denitrification. The average removal rate of ammonia nitrogen and total nitrogen were 76.5% and 76.1% respectively, while the removal of ammonia nitrogen by brick slag had little effect.3. The increase of hydraulic load had great influence on the COD, ammonia nitrogen, total nitrogen and nitrogen oxide of the wetland system. The COD of wetland effluent increased along with the increase of the organic matter concentration, and the concentration of oxidized nitrogen decreased significantly with the increase of the load. The concentration of NO₃^--N decreased from 63.44mg/L to 4.16mg/L ? The removal of phosphorus in the wastewater mainly rely on the adsorption precipitation of brick slag. Total phosphorus was mainly remved in the district 1 of the wetland, and the environmental temperature changes has little effect on the removal of TP. Temperature decrease resulted in the total COD removal rate decrease from 87.8% to 74.8% in wetland system. Because of the low temperature restrained the activity of nitrifying bacteria, the removal rate of NH₄⁺-N and TN significantly decreased. The removal rate of NH₄⁺-N and TN were reduced from 76.5%, 76.5% to 48.3%?47.9%.4. The main way to remove nitrogen in the three-stage enhanced nitrification wetland system is nitrification and denitrification, it took up about 67.19 percent of removed nitrogen.Followed by was the accumulation of the substrate, accounted for 30.05 percent. The cumulative effect of matrix was the main way of phosphorus removal in constructed wetland systems, accounts for about 86.19 percent. Plants uptaking and microbe assimilation made little contribution to nitrogen and phosphorus removal of the wetland system. The zeolite layer of wetland system mainly carried on nitrification, and denitrification also existed. The district 1 of the wetland had the strongest potential of nitrification and denitrification, which were 0.0071 mg/?g?h? and 0.0227 mg/?g?h?,respectively. The potential in district 1 and district 2 were revatively low.5. The typical crystalline structure in the zeolite surfaces was conducive to attachment and growth of the microorganism. The biofilm on the surface of zeolite was thick after biofilm formation three-stage constructed wetland. The biofilm was not as thick as that in brick slag surface. It mainly was anaerobic microbial in brick slag surface, and biomass is relatively small. The large numbers of the surface all were cocci and bacilli, and there were also a small amount of filamentous bacteria on the brick slag surface.6. Microbial diversity is rich in zeolite, Proteobacteria is the first dominant bacteria of zeolite in three-stage artificial wetland. Microbial genus on the surface of zeolite mainly were Nitrosospira and Thauera, and the existence of Thauera showed that zeolite layer had a certain denitrification. The spatial distribution of microorganisms in the brick slag layer of the wetland is not uniform while it was mainly through most of the denitrifying bacteria in the Firmicutes, Proteobacteria, Chloroflexi and Bacteroidetes to reduce the oxidized nitrogen to nitrogen.