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Research on the Efficiency of Circle-Flow Constructed Wetland Process for Swine Wastewater Treatment and Zeolite Regeneration

Author: LiuJing
Tutor: DingWeiMin
School: Nanjing Agricultural College
Course: Agricultural Biological Environmental and Energy Engineering
Keywords: swine wastewater circle-flow constructed wetland natural Ca-form zeolite aerated regeneration chemistry regeneration
CLC: X713
Type: Master's thesis
Year: 2009
Downloads: 8
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Abstract

Research on the efficiency of circle-flow constructed wetland (CFCW) process for swine wastewater treatment because of high concentrations of organic contamination, ammonia nitrogen (NH3-N), and suspended solids in swine water. Testing natural Ca-form zeolite’s regeneration process to resolve the problem that zeolite adsorbs NH3-N becoming saturation. Main results are as follows:1 Through a serious of sequence batch experiments, researching the NH3-N adsorption capacity of natural Ca-form zeolite, The results show that the adsorption isotherm of Ca-zeolite for NH3-N consistents with Freundlich equation, and the maximal adsorption capacity is as high as 38.18 mg/g.2 Researching on the efficiency of aeration regeneration and chemistry regeneration to NH4+-zeolite by seting 4 kinds of aeration intensities and studying the effect of aeration intensity on NH4+-zeolite regeneration, and comparing with natural regeneration, NH4+-zeolite aeration regenerate is best when aeration intensity is 20 ml/min. NH3-N and NO3--N have notable go up equally after 41 d, NH3-N reaches 43 mg/L, NO3--N reaches 68 mg/L.3 Comprehensively comparing the regeneration effects of select the best chemistry regeneration solvent from six different chemistry solvents, and optimize the working conditions of the best chemical solvent., the regenerate containing CaCl2 and NaCl have the optimal regeneration effect. With the temperature increasing, the regeneration effect of NH4+-zeolite is increased correspondingly, and the release rate of NH3-N increases significantly after 4 hour’s regeneration. With pH ranging from3.0 to 11.0, the regeneration effect of NH4+-zeolite is similar. Comprehensively considering the regeneration cost and the efficiency, when the useful content of regenerant is 0.64 mol/L, the ratio of NaCl to CaCl2 is 7 to 3, the natural Ca-form zeolite have optimal regeneration effect.4、Taking the simulated swine wastewater as the object to inspect the efficiency of CFCW for swine wastewater treatment. In CFCW operated stage, NH3-N high concentration entering constructed wetland system is between 600 and 800 mg/L, NH3-N concentration leak from constructed wetland system is 150-260mg/L, the elimination rate of system to treat NH3-N reachs 61% to 76%, but in the stage of CFCW start, the NH3-N concentration of entering constructed wetland system is 558～883 mg/L, but the NH3-N concentration leak from constructed wetland system is less than 0.1 mg/L, the elimination rate reaches as high as 99.9%. elimination rate of NH3-N in the CFCW does not drop, but also the NH3-N concentration leak from constructed wetland system higher than the requests that raises pigs the waste water NH3-N biggest emission standard is 80 mg/L. Natural Ca-form zeolite in CFCW has achieved saturated to the NH3-N adsorption after a year. Constructed wetland operation stage, the CODCr concentration entering constructed wetland system is 250～500 mg/L, leak from constructed wetland system is 30～80 mg/L, elimination rate of the constructed system for CODCr is about 78%～92%, but comparing with CFCW start stage, the removal effect of CODCr is good, its removal just drop about 8%Aeration regeneration experiments on CFCW indicate that NH3-N concentration in CFCW reach nearly 400 mg/L, NH3-N 150 mg/L, NH4+-zeolite regenerative effect is obvious. Chemistry regeneration on CFCW, the NH3-N concentration increase from 35 mg/L to 533 mg/L, rising more than 200 mg/L. Test results show that the increased aeration and add combinatorial chemistry NaCl+CaC2 regeneration, and NH4+-zeolite regenerative effect is better.

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