HYDROGEN SULFIDE PRODUCTION FROM STORED LIQUID SWINE MANURE: A LABORATORY STUDY

Abstract

The production of hydrogen sulfide from stored liquid swine manure as influenced by the manure settlingcharacteristics and the initial sulfate concentration was studied in the laboratory. The manure was settled in a 30-cmdiameter 120-cm high column for 24 h and then divided into three layers based on the solids content. The manure fromdifferent layers were placed in separate closed jars and stored for 30 days at 22 2C. The total sulfide, total solids,volatile solids, pH in the manure, and the hydrogen sulfide in the effluent gas stream were measured. The sulfideproduction rate was highest for all three manure layers during the first 5-10 days of storage. The top manure layer hadthe lowest solids content and the highest sulfide concentration. However, because of the lower pH levels in the bottomlayer, the concentration of molecular H2S is higher in the bottom layer compared with the top layer. Mathematicalequations for predicting hydrogen sulfide concentration and production rates in the different manure layers were derived.Three levels of initial sulfate concentration (5.89, 110, and 275 mg/L as SO42) were used to test the effect of initialsulfate concentration in the liquid manure on sulfide production. Higher initial sulfate concentration in the manureresulted in higher sulfide concentration during the storage period. From the observations made, it was confirmed thatreducing the sulfate concentration in the water supply would help reduce the sulfide production in the pit.