Formation of organic acids and ammonia during acidogenesis of trout-processing wastewater

Abstract

A set of experiments was carried out to characterize trout-processing wastewater and to investigate biological acidification (acidogenesis) of the wastewater. Based on individual amino acids analysis and stoichiometric calculations, protein was a major organic material which composed 92.9% of chemical oxygen demand (COD) in the wastewater Three concentrations of COD set up in a ratio of 1:4:9 made by dilution of raw wastewater (11.4, 45.7, and 102.7 g COD/L) were tested for acidogenesis in batch mode. Production of acetate, propionate, isobutyrate, butyrate, methylbutyrate, and valerate was monitored. Acetate production was predominant in all treatments, and amounts of acetate and butyrate were proportional only to the initial wastewater strength. The formation of odd-chain organic acids (propionate, methylbutyrate, and valerate) increased with decreasing initial wastewater strength. Based on stoichiometric calculations, total conversions of organics in the wastewater to short-chain organic acids at initial COD concentrations set up in a ratio of 9:4:1 were respectively 52.1%, 74%, and 79.6%.