Use of Short Term Microbial Bioassays to Evaluate Toxicity of Hospital Wastewaters

Microorganisms perform several processes on the earth, many of which are of critical importance. Heterotrophic microbes are very much helpful in wastewater treatment. Wastewater is one of the main issues in the context of environmental pollution. The concern becomes more intense if the wastewater comes from health care industry as hospital effluents are heavily loaded with pathogenic microorganisms, pharmaceuticals partially metabolized, radioactive elements and other toxic chemical substances, such as, antitumor agents, antibiotics and organohalogen compounds. Indeed, some of the substances found in wastewaters are genotoxic and are suspected to be a possible cause of cancer. Besides treatment of wastewater, microorganisms also perform a chief task in monitoring the toxicity of wastewaters prior to treatment as well as after treatment. Hence, through this review the authors intend to draw attention on the evaluation of possible biological toxicity and mutagenicity of hospital wastewaters using biological assays. A range of toxicity and genotoxicity bioassays has been developed to establish the toxicity level of wastewater against different organisms, such as, bacteria, algae, plants, invertebrates, fish and mammals. Problems with standardization of the organisms, requirements for special equipment and skilled operators, long duration of the assay, lack of reproducibility and crucially, sacrificing a great number of animals (in case of animal bioassays) are the major disadvantages associated with animal and plant bioassays. Therefore, evaluation of biological effects using short term microbial bioassays (a rapid, simple, sensitive and cost effective method) seems to be relevant tool for assessing the mutagenic potential and health hazard caused by hazardous effluents (as from hospitals) to human beings and other higher aquatic and terrestrial organisms, upto a considerable extent.