Enhanced recovery of ammonia from swine manure anaerobic digester effluent using gas-permeabie membranes and aeration

摘要

Atmospheric ammonia pollution from livestock wastes can be reduced using gas-permeable membrane technology. This technology converts ammonia contained in the manure into ammonium salt for use as fertilizers. In this study, gas-permeable membrane technology was enhanced using aeration combined with nitrification inhibition to both increase the pH of the manure and the capture of ammonia by the membrane system. Two separate effluents from covered anaerobic lagoons with initial ammonia levels of 2089 mg/L and 1375 mg/L were tested using bench reactors of 1.5-L effective volume. The aeration rate was low (180 mUmin) to prevent nitrification but sufficient to significantly increase pH. A control membrane manifold treatment without aeration was included in all the experiments. The pH of the liquid manure with aeration rose from 8.6 to 9.2 while the pH of the manure without aeration decreased from 8.6 to 8.1. The total amount of ammonia removed using aeration was compared to the amount removed without aeration. With aeration, 97-99% of the ammonia was removed in about 5 days of operation. In contrast, it took about 25 days to remove the ammonia when aeration was not used. Therefore, the recovery of ammonia from digested effluent using the gas-permeable membrane technology was five times faster with the addition of low-rate aeration. This improvement represents a significant cost reduction in equipment for implementation of the technology.