Review article
A review on hospital wastewater treatment: A special emphasis on occurrence and removal of pharmaceutically active compounds, resistant microorganisms, and SARS-CoV-2

https://doi.org/10.1016/j.jece.2020.104812Get rights and content

Highlights

  • The organic fraction in hospital wastewater has low biodegradability index.

  • Some bacteria in hospital effluents develop resistance to antibiotics and other drugs.

  • SARS-CoV-2 RNA in wastewater and COVID-19 affected people are positively correlated.

  • CWs and MBR have been efficient in terms of ARG and ARB inactivation.

  • 30–80 mg min/L of chlorine can inactivate various ARG, ARB, and viruses.

Abstract

The hospital wastewater imposes a potent threat to the security of human health concerning its high vulnerability towards the outbreak of several diseases. Furthermore, the outbreak of COVID-19 pandemic demanded a global attention towards monitoring viruses and other infectious pathogens in hospital wastewater and their removal. Apart from that, the presence of various recalcitrant organics, pharmaceutically active compounds (PhACs), etc. imparts a complex pollution load to water resources and ecosystem. In this review, an insight into the occurrence, persistence and removal of drug-resistant microorganisms and infectious viruses as well as other micro-pollutants have been documented. The performance of various pilot/full-scale studies have been evaluated in terms of removal of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), PhACs, pathogens, etc. It was found that many biological processes, such as membrane bioreactor, activated sludge process, constructed wetlands, etc. provided more than 80% removal of BOD, COD, TSS, etc. However, the removal of several recalcitrant organic pollutants are less responsive to those processes and demands the application of tertiary treatments, such as adsorption, ozone treatment, UV treatment, etc. Antibiotic-resistant microorganisms, viruses were found to be persistent even after the treatment of hospital wastewater, and high dose of chlorination or UV treatment was required to inactivate them. This article circumscribes the various emerging technologies, which have been used to treat PhACs and pathogens. The present review also emphasized the global concern of the presence of SARS-CoV-2 RNA in hospital wastewater and its removal by the existing treatment facilities.

Introduction

Hospitals play a pivotal role in the well-being of humanity and facilitate research in the field of medical advancement. They help in complementing various parts of the health system and provide continuous services to tackle the complex health conditions of human beings [1]. The healthcare sector is one of the largest employers in the United States (US), with more than six million people employed at US hospitals with around 36.3 million admissions in 2018 [2]. The worth of the Indian health sector has been projected to jump from 140 billion U.S. dollars in the year 2016 to 372 billion dollars by the year 2022 [3]. With the onset of the COVID-19 pandemic, hospitals and other health care facilities have been responsible for giving a chance for survival to more than 20 million people affected by the SARS-CoV-2 virus. Concerning the ever-growing expansion of medication and health care activities in the hospital, the generation of large quantities of wastewater and its management is an impounding challenge in environmental engineering [1]. On average, hospitals in developed countries generate a significantly higher volume of wastewater as compared to hospitals in developing countries [1], [4], [5], [6], [7], [8].

Hospital wastewater (HWW) is also characterized by the presence of various emerging contaminants, such as pharmaceutically active compounds (PhACs), several microorganisms including antibiotic-resistant bacteria (ARB), antibiotic-resistant genes (ARG), persistent viruses, etc. [9], [10], [11], [12]. Generally, HWW comprises high biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia, and nitrogen content, and their concentration is higher compared to the domestic wastewater [13], [14]. BOD is the amount of oxygen consumed by microorganisms to decompose organic matter under aerobic conditions at a specific temperature and duration of time, while COD is the amount of oxygen equivalents consumed in the chemical oxidation of organic matter by a strong oxidant [15], [16]. Hence BOD can be referred to as the biodegradable fraction of wastewater, while COD is the measure of both biodegradable and non-biodegradable organic compounds. The ratio of BOD and COD of wastewater is referred to as the biodegradability index [16], [17]. The biodegradability index of HWW is also lower than the municipal wastewater, making them difficult to treat by conventional biological systems [13], [14], [18]. Many of the recalcitrant organic compounds present in HWW, such as PhACs, are highly toxic with very low drinking water equivalent limit (DWEL) values making them a considerable threat to the environment [19]. Viruses, ARB, and ARG continue to survive even after the treatment of HWW, and their release to the aquatic ecosystem imposes a significant threat to the environment [6], [20].

Over the years, various treatment technologies, including the biological methods, such as activated sludge process (ASP), membrane bioreactor (MBR), moving bed bioreactor (MBBR), constructed wetlands (CWs), the advanced oxidation processes, such as photocatalysis, Fenton process, etc. have been implemented to treat HWW [8], [13], [21], [22]. Many lab-based studies targeting the removal of PhACs and other recalcitrant contaminants present in HWW are reported in several works of literature, but only a handful number of pilot-scale and full-scale studies have been conducted addressing their treatment concerning HWW [8], [19], [23]. Treatment of HWW is not an easy feat, considering the vast quantities of wastewater generated having high COD, nitrogen, and PhAC content. Furthermore, the onset of COVID-19 pandemic has shifted the focus to the removal of viruses, ARG, ARB present in HWW, and this area has not been substantially addressed. Given the necessity and recent emergence of this profound health and environmental concern, the present review stems from the unavailability of comprehensive documentation in this area.

In this review, a thorough characterization of HWW has been conducted considering the variation of the characteristics of HWW in different regions. A detailed insight has been provided on the occurrence of PhACs, viruses, and several microorganisms in various HWW. A special emphasis has been given to the presence of SARS-CoV-2 and SARS-CoV in wastewater, keeping in mVerlicchiind the COVID-19 pandemic scenario. In recent years, various reviews were published on the characterization of hospital wastewater and their treatment. Khan et al. [24] reviewed the occurrence of pharmaceuticals in HWW and the performance of primary, secondary, and tertiary treatment techniques for their removal. Orias and Perrodin [25] reviewed the characteristics of hospital wastewater and its eco-toxicity. Verlicchi et al. [26] also summarized the characteristics of hospital wastewater and their treatment using conventional and advanced processes. However, most of these studies cover lab-based technologies that are still in developing stages. Performance of pilot/full-scale treatment units dedicated to the simultaneous removal of recalcitrant organic compounds, physicochemical parameters, such as BOD, COD, total suspended solids (TSS), ammonia nitrogen, total nitrogen, pathogens, etc. from HWW has not been sufficiently addressed. This review primarily focuses on the performance of various operational pilot-scale and full-scale treatment units by various biological and advanced oxidation treatment technologies dedicated to the treatment of HWW. The performance of these treatment units in terms of removal of BOD, COD, ammonia nitrogen, TSS, and PhACs has been extensively discussed. The inactivation of persistent ARG, ARB, and virus are also critically analyzed. Furthermore, the various emerging technologies to combat PhACs, ARB, ARG, such as photocatalysis, anodic oxidation, Fenton-based processes, and treatment using nanoparticles have also been discussed. A special emphasis is provided on the occurrence and removal of SARS-CoV-2 and SARS-CoV to catalyze the research on the present global need.

Section snippets

Water consumption and effluent generation from hospitals

Hospitals around the globe require large amounts of water for their proper functioning for various health care facilities. HWW, among all other healthcare waste, imposes a grave hazard to human health and the environment because of their capability to enter watersheds, pollute surface and groundwater, when inappropriately handled and disposed to hydrosphere [27]. According to the World health organization (WHO) guidelines for the proper functioning of healthcare facilities, 40–60 L/day of water

Characteristics of hospital wastewater

The effluent coming out of different hospitals are rich in PhACs, microorganisms, and are characterized by high COD, BOD, ammonia, nitrate, total nitrogen (TN), TSS, total organic carbon (TOC), total Kjeldahl Nitrogen (TKN), etc. Qualitative analysis of medical waste of 10 hospitals in Iran indicated that liquid waste had a 16.70% contribution to hazardous–infectious waste [33]. The discharge from hospitals can be classified into four broad categories, i.e., blackwater, greywater, stormwater,

Removal of BOD, COD, TSS, nitrogen, and PhACs

Over the past two decades, various treatment processes have been implemented and up-scaled to pilot or full-scale treatment system for treating HWW. The details of various pilot/full-scale treatment units have been mentioned in Table 2. The performance of the various pilot/full-scale treatment technologies in treating the different components of HWW has been discussed in the following sections and has been depicted in Fig. 4. A schematic representation of the source of different pollutants in

Emerging technologies for removal of PhACs and various pathogens

ARG, ARB, viruses, recalcitrant organic compounds, such as PhACs, personal care products, X-ray contrast media form an integral part of the HWW. The presence of these components makes the HWW less biodegradable, toxic, and difficult to treat [163]. Over the past decade, research has been focused on the removal of PhACs, ARG, ARB, and other recalcitrant organic compounds by various emerging technologies, such as photocatalytic degradation, photolysis, anodic oxidation, Fenton’s processes,

Challenges in HWW management

One of the major challenges in the field of HWW management is the monitoring and detection of the pollutants [199]. PhACs and other recalcitrant organic compounds are present in the HWW is the range of ng/L to μg/L, which require highly sensitive to quantify [19], [36], [169], [200], [201]. Proper detection of such contaminants in necessary to implement proper legislations for HWW management [199]. Only a few guidelines pertaining to hospital waste management, such as “Effluent Guidelines and

Summary of findings

Hospitals are significant contributors to a large amount of complex wastewater to inland surface water and municipal sewer. Furthermore, it was found that hospitals in developed countries generated much higher quantities of wastewater than developing countries. HWW comprises a wide range of contaminants, such as recalcitrant PhACs, viruses, ARG, ARB, and high nutrient content. A low biodegradability index makes the treatment of HWW more challenging. PhACs, such as diclofenac and ciprofloxacin,

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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