A review on hospital wastewater treatment technologies: Current management practices and future prospects

Substantial quantities of wastewater effluents and biomedical waste consisting of different toxic environmental pollutants such as pharmaceutically active compounds, organic contaminants, heavy metals, radioactive isotopes, and pathogenic microbes are released from the healthcare systems. Therefore, the development of efficient treatment technologies is urgent requirement for the environmental protection. Physicochemical parameters like octanol-water partitioning and solid-water distribution coefficient are used for estimating the fate and distribution of hospital effluents. This present review summarizes a compendium of the types of contaminants dis-charged from healthcare facilities, global directives and for hospital wastewater (HWW) management and imparts a comprehensive insight into conventional and modern technologies, and probable up gradation in the current designs for efficiently treating hospital effluents. Majority of countries across the globe have not implemented adequate rules and guidelines for on-site processing or specific treatment of hospital effluents. Generally, HWW is treated by conventional wastewater treatment plants (WWTPs) and the contaminant removal rates for primary, secondary, and tertiary treatment steps were reported to be 20-50 %, 30-70 %, and >90 % respectively. The traditional treatment methods; membrane bioreactor, activated sludge process, trickling filters, and constructed wetlands significantly (<80 %) reduce BOD, COD and TSS but not effective for removal of contrast media drugs, psychiatric drugs and recalcitrant antibiotics. Advanced treatment strategies such as advanced oxidation, ozonation, photo Fenton oxidation, nanoremediation, and hybrid technologies need to be studied extensively for achieving complete contaminant removal. Ozonation eliminates up to >93 % of various recalcitrant antibiotics present in the HWW and is being used at the pilot plant scale. However, X-ray contrast media remain untreated by ozonation. Advanced oxidation processes (AOPs) effectively remove antibiotics and pathogenic microbes from HWW, and as a pre-treatment process also enhance the biodegradability of pollutants. Nanocomposites can improve biodegradability and also assist in photo-catalytic degradation of HWW contaminants. Electrocoagulation and photo-catalytic methods showed removal efficiency up to >99 %. Integrated methods consisting of biological methods and AOPs have been found to remove >98 % of different pharmaceuticals and ARGs/ARBs. AOPs can be employed either as pre or post-treatment strategy in integration with biological processes, adsorption, and filtration for treating recalcitrant compounds. Membrane bioreactors (MBR) in association with AOPs are also found to be promising for the pre-treating HWW at full scale. The energy and cost demand associated with these methods can also limit their application owing to the high flow rates of HWW. Moreover, the hybrid methods still necessitate further development and optimization for large scale application.