The Influence of some Treated - and Untreated Industrial Wastewaters on Soil Microbial Respiration and Biomass Carbon

The use of waste water may help sustainable soil fertility via improving the physical, chemical and biological soil characteristics. The main purpose of this study was to determine the effect of industrial wastewaters from three factories, Esfahan Steel Company- Zobahan-, Esfahan Mobarakeh Steel Corporation- Foolad Mobarakeh- and Esfahan Polyacryl Company; in two forms (treated and untreated) on C mineralization, microbial biomass C and metabolic quotient (qCO2). The response of soil microbiological indices such as C mineralization, microbial biomass C and qCO2 to the applications of effluent wastewaters over 112 days of incubation period was evaluated under laboratory conditions. Results showed that the effect of industrial wastewaters on C mineralization was significant and the untreated wastewater from Polyacryl Company increased C mineralization significantly. Other wastewaters decreased C mineralization or did not have a significant effect. Microbial biomass C increased during the first and second month of the incubation period, but during the third month the untreated wastewater from Zobahan, treated and untreated wastewater from Foolad Mobarakeh decreased the amount of soil microbial biomass C. The effect of industrial wastewaters on qCO2 values was substantial and variable. There was a decrease in qCO2 during the first and second month of incubation period. The application of untreated wastewater from Zobahan, treated and untreated wastewaters from Foolad Mobarakeh increased qCO2 during the third month of soil incubation. Briefly, the utilization of wastewaters initially increased C mineralization, microbial biomass C and reduced qCO2, while at the end of the incubation time most wastewaters decreased C mineralization, microbial biomass C and increased qCO2. This might indicate that the labile organic matter contents in wastewaters were reduced and the concentrations of heavy metals in soil were increased during incubation period.