Assessment of Microbial and Ecotoxicological Qualities of Industrial Wastewater Treated with Membrane Bioreactor (MBR) Process for Agricultural Irrigation

Abstract

The issue tending toward alternative water resources tremendously becomes important for supplying the increasing water demand all over the world. It may be a good option to evaluate industrial effluents for agricultural irrigation. However, industrial effluent must be cleansed from the factors such as salt, toxic compounds, and microbial load that possibly cause negative effects on soil during agricultural irrigation. In this study, microbiological qualities and toxicity conditions of water sources such as membrane bioreactor (MBR) influent, MBR effluent, and mixture of MBR effluent and reverse osmosis (RO) permeate (MBR:RO = 2:1) were analyzed and evaluated according to irrigation standards. Total aerobic heterotrophic bacteria (TAHB), total coliforms (TC), fecal coliforms (FC), fecal streptococci (FS), and Clostridium spp. were screened and enumerated as indicator microbial groups for the microbial quality of water samples. Analyses of indicator microorganisms showed that loads of different bacterial groups decreased by 5.2 and 6.66 log units at maximum levels in MBR and MBR + RO system at the end of treatment. Also, evaluation of the toxicity effects of MBR effluent and MBR + RO permeate waters on Vibrio fischeri and Daphnia magna was investigated. None of the samples showed any acute toxic effect on D. magna after 48 h and V. fischeri in 5 min and 15 min. From the outputs of this study, it can be said that industrial effluents treated by advanced filtration technologies may provide a significant source of water for agricultural irrigation. This option can have positive impacts on both environmental and economic factors.