Wastewaters have been reported to contain SARS-CoV-2 RNA that could be transmitted and contaminate the aquatic environment [42]. Kumar et al. [43] suggested that the presence of viral loads in wastewater could indicate that the transmission of SARS-CoV-2 through wastewater is possible, especially in countries where sewer systems are not effective enough in removing the virus. Wastewaters from hospitals and quarantine centers for COVID-19 may contain high concentrations of the viral particles, and, thus, effective treatments of hospital wastewater should be strictly enforced to inactivate the virus and prevent transmission [44,45]. Zhang et al. [19] reported high concentrations of SARS-CoA-2 RNA (0.5 to 18.7 × 10³ copies/L) in hospital septic tanks, even after disinfection with sodium hypochlorite (800 g/m³). Langone et al. [28] reported that SARS-CoV-2 RNA particles were still present in wastewater from secondary treatment plants, but they could be completely removed in wastewater treatment plants (WWTPs) equipped with tertiary waste treatments. Balboa et al. [46] reported that no SARS-CoV-2 RNA was found in well-treated effluent or sludge.

Wastewater contains high concentrations of micro-organisms, organic and inorganic substances that could contribute to the natural degradation of viral RNA [47]. However, Yang et al. [31] reported that sewage sludge in WWTPs could harbor a high abundance of SARS-CoV-2 that could survive for months, as the complex organic matter of the sludge could protect the virus from inactivation. Balboa et al. [46] noted that untreated sewage sludge has high concentrations of viral particles and suggested that thickened sewage sludge was a suitable sampling area for COVID-19 monitoring. Thickened sludge with a high abundance of viral RNA formed a suitable spot for COVID-19 incidence monitoring.

SARS-CoV-2 in human guts, stools, and wastewater forms an important fecal-oral route transmission, especially in countries where wastewater treatment facilities are not adequate to remove the viral particles [25,30,48]. Municipal wastewaters in many countries have been used for cleaning, flushing toilets, watering agricultural land, or even for drinking in certain big cities with limited freshwater supply. Thus, the transmission of SARS-CoV-2 RNA via wastewater discharges is a possible route for infection in humans [25]. Zhang et al. [19] reported that viruses in fecal materials in septic tanks can contribute to the spread of SARS-CoV-2 through drainage pipelines. Cervantes-Avil’es et al. [21] reported that SARS-CoV-2 has been detected in wastewater treatment plants, manholes, sewer networks, and various sludge treatment facilities in Europe, North America, South America, and Asia. In fact, the increase of SARS-CoV-2 genetic materials in the wastewater is positively correlated with the number of active COVID-19 patients and can be used as an indicator for the environmental surveillance of the COVID-19 pandemic [43]. Albastaki et al. [20] showed a direct and significant correlation between SARS-CoV-2 viral load in wastewaters and the number of cases in the United Arab Emirates. Gwenzi [25] suggested three main pathways as to how SARS-CoV-2 can be transmitted via the fecal-oral route, all of which are related to the environment (contaminated drinking water), fishery resources (raw or semi-cooked foods from SARS-CoV-2 contaminated waters), or aquaculture products (wastewater-based aquaculture).

The transmission of SARS-CoV-2 via wastewater could eventually contaminate surface waters, as the virus could not be eliminated by conventional secondary treatment of sewage [24]. These viral particles could eventually get to the human through the aquatic food chain and aquatic-based resources such as fish and shellfish [21]. The survival time of SARS-CoV-2 in waters strongly depends on temperature, oxidative chemicals, the concentration of suspended solids and organic matters, and predation along the food chain where SARS-CoV-2 could survive for months in waters with high suspended particles [28,31]. Balboa et al. [46] reported that SARS-CoV-2 has a strong affinity for biosolids. Thus, turbid rivers and lakes with high suspended solids contents are more susceptible to carrying viral particles and form an important route for the viral spread in a community. Wang et al. [49] reported that river hydrology plays an important role in the long transmission route of SARS-CoV-2.

Grossly inefficient wastewater treatment in developing countries could make the waterborne transmission of SARS-CoV-2 a serious threat to the environment and people [45]. Make-shift quarantine centers that do not have adequate facilities for treating SARS-CoV-2 contaminated wastes were commonly used to house thousands of COVID-19 patients, as hospitals were full to the brim. These poor developing countries are at risk, as the absence of proper management of COVID-19 related wastes including wastewater and medical wastes might further spread the virus [1,50]. Adelodun et al. [44] offerred useful suggestions for low-income countries such as use of chlorination, ozonation, and UV radiations to deactivate SARS-CoV-2 in their wastewater and prevent/minimize the COVID-19 outbreaks. In low-income countries, where waste treatment facilities are inadequate to remove the virus, it is very important to ensure that wastes should be disinfected by cheap but effective disinfectants and to prevent the discharge of the wastewater to natural water bodies.

With the advent of COVID-19 around the globe, there is a massive surge of medical wastes including plastics, antiviral medicines and drugs, and disinfectants that potentially affect the aquatic environment. With the emergence of COVID-19, there has been an increased use of disinfectants to inactivate the virus on surfaces. DeLeo et al. [18] reported that disinfectant Quat (quaternary ammonium compounds) was commonly used during the COVID-19 pandemic in many countries since it has strong biocidal properties and is effective against bacteria and viruses. Fortunately, the ecotoxicity of this disinfectant is minimized due to its high biodegradation rate and readily absorbed to particles in water and sediment. In addition, chlorine (ClO₂), sodium hypochlorite (NaOCl), or ultraviolet (UV) water treatment can be used, as they are relatively cheap and easily available [24]. However, high doses of chlorine and sodium hypochlorite (~6700 g/m³) required to completely remove SARS-CoV-2 RNA had high disinfection by-product residual with significant ecological risks [19]. Thus, the ecological risk of disinfection by-product residuals needs to be evaluated.

Currently, COVID-19 vaccination is compulsory to acquire immunity against SARS-CoV-2 by minimizing spread, severity, and death. COVID-19 vaccine vials and ancillary supplies are considered infectious materials. Therefore, the disposal of these materials also requires standard operation waste treatment procedures. Treatment by disinfecting solutions such as chlorine prior to final disposal is necessary to avoid contamination to both humans and the environment. Biomedical waste generated daily is a serious concern, as many would end up in the water and act as sources of chemical pollutants or as substrates for viral particles [51]. The increased use of antiviral and antibiotics also results in increased waste of these medicines in water bodies. Nibamureke and Wagenaar [17] reported that medicinal waste could result in impaired fish reproduction. Tarazona et al. [16] developed models to predict the impacts of antibiotics and antiviral drugs on the ecology of aquatic ecosystems and showed sub-lethal effects on fish.

Persistent wastes such as plastic materials become a global pollution problem because they do not biodegrade easily and could be transported to aquatic ecosystems by winds, storm drains, and rivers. These plastic materials undergo fragmentation and break down into smaller plastic particles of difference sizes categorized as mesoplastics (5 mm to 25 mm), microplastics (<5 mm), and nanoplastics (1 nm to 1 µm) through various mechanical, chemical, and weathering processes [13]. Plastic materials submerged in water leached out heavy metals including lead, cadmium, antimony, and copper, in addition to toxic leachable organic substances related to plastic additives and contaminants [52]. Fadare and Okoffo [53] reported an unprecedented rise in the global production of polymer-based face masks (single use), resulting in an increase in microplastics pollution. Many of these toxic pollutants can enter the aquatic food chain, which could accumulate in aquatic foods and transfer to humans. Pan et al. [54] also reported an average of 246 items m⁻³ of microplastics in a Chinese river consisting of PP (polypropene) and PE (polythene) as the major polymers.

With 206.2 million COVID-19 cases and 4.4 million deaths in 220 countries as of the 13 August 2021, billions of pieces of personal protective equipment (facemasks, gloves, aprons, etc.) ended up as waste that could pose as health hazard to the environment and human lives if they are not properly treated and managed. Benson et al. [14] estimated more than 12 billion (equivalent to 105,000 tonnes) medical and fabric masks were discarded monthly in African countries, mainly due to the increased consumption of single-use plastics for surgical masks, medical gowns, face shields, safety glasses, protective aprons, sanitizer containers, plastic shoes, and plastic gloves for the protection from SARS-CoV-2. Ardusso et al. [13] also reported that textile fibers for PPE are impregnated with silver (Ag) and copper (Cu) nanoparticles to reduce the infection and spread of SARS-CoV-2. These antiviral textile wastes are a form of an emerging contaminant with long-term negative repercussions on aquatic environments and biota. Most plastics used in medical applications are made from polypropylene, and the plastic residues are classified as biohazardous materials. Studies by Nzediegwu and Chang [50] and Gwenzi [25] have shown that coronavirus can survive on material surfaces between six to nine days. Aragaw [55] noted that face masks are easily ingested by big animals high in the aquatic food chain such as fishes, turtles, and water birds, with enormous effects on their populations and survival. Humans at the end of the aquatic food chain would have a high risk of eating contaminated aquatic foods. Based on past studies, Latchere et al. [56] illustrated the toxicity of microplastics (MPs) and nano plastics (NPs) at the species, community, and ecosystem levels, demonstrating the contamination of plastics through the aquatic food chain. Despite the plethora of problems associated with different experiments and analyses, many studies clearly demonstrated the toxicity of plastics in the freshwater-marine continuum, as well as along the trophic transfer. The improper disposal and disinfection of bottles and containers used in healthcare and treatment facilities could be another potential source of viral transmission. Thus, developing countries with poor waste management facilities are at risk.