Keywords

1 Introduction

Hospital wastewater (HWW) is the wastewater discharged from all hospital activities, both medical and non-medical, including activities in surgery rooms, examination rooms, laboratories, nursery rooms, radiology rooms, kitchens, and laundry rooms. Hospitals consume consistent quantities of water per day. The consumption in hospitals in industrialized countries varies from 400 to 1,200 L per bed per day [1], whereas in developing countries this consumption seems to be between 200 and 400 L per bed per day [2].

HWWs are considered of similar quality to municipal wastewater [3, 4], but may also contain various potentially hazardous components which mainly include hazardous chemical compounds, heavy metals, disinfectants, and specific detergents resulting from diagnosis, laboratory, and research activities [5,6,7,8,9]. Higher concentrations of pharmaceutical compounds (PhCs) were found in hospital effluents than those found in municipal effluents [10, 11]. According to recent literature [8, 12,13,14], HWWs may be considered a hot spot in terms of the PhC load generated, prompting the scientific community to question the acceptability of the general practice of discharging HWWs into public sewers [8], where they are conveyed to municipal wastewater treatment plants (WWTPs) and co-treated with urban wastewaters (UWWs) [8, 13, 15, 16].

HWWs represent an important source of PhCs detected in all WWTP effluents, due to their inefficient removal in the conventional systems [17,18,19,20]. Indeed, HWWs may have an adverse impact on environmental and human health through the dissemination of antibiotics and antibiotic resistant bacteria in rivers [21,22,23,24]. The correct management, treatment, and disposal of HWWs are therefore of increasing international concern.

In European countries efforts are being made to improve the removal of PhCs by means of end-of-pipe treatments, and different full scale WWTPs have already been constructed for the specific treatment of hospital effluents [25].

In order to highlight this area of research in the rest of the world, this chapter provides an overview of the current management and treatment of HWWs in Asia, Africa, and Australia.

2 Treatment Scenarios of HWWs

Different treatment scenarios are applied in different countries for the treatment of HWWs. Table 1 lists all the treatment scenarios applied, with the corresponding references. Hospital effluents are usually discharged into the urban sewer system, where they mix with other effluents before finally being treated in the sewage treatment plant (co-treatment). This practice is common in Australia, Iran, Egypt, India, Japan, South Africa, and Thailand. However, in many other developing countries, such as Algeria, Bangladesh, Congo, Ethiopia, India, Nepal, Pakistan, Taiwan, and Vietnam, hospital effluents can represent a major source of toxic elements in the aquatic environment since the effluents are discharged into drainage systems, rivers, and lakes without prior treatment. According to Ashfaq et al. [41], no hospital, irrespective of its size, has installed proper wastewater treatment facilities in Pakistan. In Taiwan, some hospitals discharge their wastewaters (legally or illegally) directly into nearby rivers with scarce treatment at all [44]. Of 70 governmental hospitals from different provinces of Iran, 48% were equipped with wastewater treatment systems, while 52% were not. Fifty-two percent of the hospitals without treatment plants disposed their raw wastewater into wells, 38% disposed it directly into the environment and the rest into the municipal wastewater network [35]. Comparison of the indicators between effluents of wastewater treatment systems and the standards of Environmental Departments shows the inefficiency of these systems and, despite recent improvements in hospital wastewater treatment systems, they should be upgraded.

Table 1 Treatment scenarios of hospital effluents in different countries
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In Indonesia, only 36% of hospitals have a WWTP and 64% of wastewater is discharged directly into receiving water bodies or using infiltration wells. Mostly, Hospital Wastewater Treatment Plants (HWWTP) use a combination of biological-chlorination processes with the discharge often exceeding the quality standard, such as Pb, phenol, ammonia free, ortho-phosphate, and free chlorine. The low quality of discharges into HWWTPs, especially of toxic pollutants (Pb and phenol), can be caused by not yet optimal biological-chlorination process [34].

An interesting investigation was carried out in 2004 in Kunming city, a large city in the southwest of China. Of 45 hospitals there were 36 with wastewater disinfection equipment. In the same year, the wastewater treatment facilities of 50 hospitals were investigated in Wuhan city, which is the biggest city in the central southern part of China. It showed that there were 46 hospitals with wastewater treatment facilities, and for only about 50% of them, the effluent quality from wastewater treatment facilities accorded with the national discharge standard [29, 46, 47].

In Iraq, most of the hospitals have their own treatment plant, but they are not capable of meeting Iraqi standards, especially in terms of nutrient and pathogen removal [38]. The scenario of hospital wastewater treatment is more stringent in countries like China, Indonesia, and the Republic of Korea, where HWW is treated onsite (specific treatment).

An effective, robust, and relatively low-cost treatment was used to disinfect HWWs during Haiti cholera outbreak occurred after the earthquake of January 2010. Two in-situ protocols were adopted: Protocol A included coagulation/flocculation and disinfection with hydrated (slaked) lime (Ca(OH)2) by exposure to high pH and Protocol B using hydrochloric acid followed by pH neutralization and subsequent coagulation/flocculation, using aluminum sulfate. This approach is currently being adapted by non-governmental organizations (NGOs) to help managing human excreta in other emergency settings, including the outbreaks of Ebola and other infectious diseases in west Africa, Philippines, and Myanmar [48].

3 Overview of the Included Studies

The main characteristics of the studies included in this chapter referring to the specific treatment of hospital effluents are reported in Table 2. The main reason for research in European countries is generally an awareness of the potential risks posed by the occurrence of PhC residues in secondary effluents and the need to reduce the PhC load discharged into the environment via WWTP effluents [25]. However, the rationale behind the studies presented in this chapter was to evaluate different options for hospital effluent treatments before discharge into public sewage or into the environment, to improve the biodegradability of hospital effluents, to avoid the spread of pathogenic microorganisms, viruses, antibiotic resistant bacteria, pharmaceuticals, and chemical pollutants, to reduce the organic load and finally, to meet the requirements of discharge standards in different countries. Of all the studies, only four deal with the occurrence of PhCs in hospital effluents, while the remaining studies take into consideration pathogenic bacteria and conventional pollutants like COD, BOD, and SS.

Table 2 List of the studies included in the overview together with a brief description of the corresponding investigations and rationale
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4 Antibiotic Resistant Bacteria in HWWs

Although antibiotics have been used in large quantities for some decades, the existence of these substances in the environment has received little attention until recently. In the last few years a more complex investigation of antibiotics has been undertaken in different countries in order to assess their environmental risks. It has been found that the concentrations of antibiotics are higher in hospital effluents than in municipal wastewater, which has higher concentration levels than different surface waters, ground water, and sea water [53]. HWWs could be a source of antimicrobial-resistant bacteria which are excreted by patients. The HWWs either flow into a hospital sewage system or directly into a municipal wastewater sewer, before being subsequently treated in a WWTP. After treatment in a WWTP, the effluent is discharged into surface waters or is used for irrigation. Studies have shown that the release of wastewater from hospitals was associated with an increase in the prevalence of antibiotic resistance. A study conducted in Australia by Thompson et al. 2012 [27] revealed evidence of the survival of antibiotic resistant strains in untreated HWWs and their transit to the STP and then through to the final treated effluent. The strong influence of HWWs on the prevalence of antimicrobial-resistant E. coli in Indian WWTPs has been revealed by Alam et al. [24] and Akiba et al. [33]. Untreated hospital and municipal wastewaters were found to be responsible for the dissemination of antibiotics and antibiotic resistant bacteria in the rivers of Pakistan [22].

In Bangladesh, a study was conducted by Akter et al. [23] concerning the effects of hospital effluents on the emergence and development of drug-resistant bacteria. They concluded that hospital and agricultural wastewater is mostly responsible for causing environmental pollution by spreading un-metabolized antibiotics and resistant bacteria. Analyses of the results obtained from South Africa indicated that HWWs may be one of the sources of antibiotic resistant bacteria in the receiving WWTP. The findings also revealed that the final effluent discharged into the environment was contaminated with multi-resistant enterococci species, thus posing a health hazard to the receiving aquatic environment as these could eventually be transmitted to the humans and animals exposed to it [43, 54].

As a result, hospitals are important point sources which contribute to the release of both antimicrobials and antibiotic resistant genes into surface waters, especially if hospital wastewaters are discharged into the receiving ambient waters without being treated.

5 Treatment Sequences for HWWs Under Review

The sequences adopted for the specific treatment of hospital effluent in different countries are reported in Table 3, along with the corresponding bibliographic reference. As can be seen, treatments differ with a trend towards MBR, followed by CAS. Most of the investigations refer to full scale plants and include the following treatment trains: CAS in China, India, Iran, and Vietnam; MBR, MBR + disinfection in China; Flocculation + Activated carbon, Flocculation + CAS in South Korea; Septic Tank + H-SSF bed + V-SSF bed in Nepal, and Ponds in Ethiopia. Seventy-eight percent of the equipped hospitals in Iran used activated sludge systems and 22% used septic tanks [35].

Table 3 Treatment sequences for hospital effluents included in the chapter
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Several pilot plants were also tested in different countries: CAS + Sand Filtration + Chlorination in India; Aerated Fixed Film Biofilter + O3 in Indonesia; CAS and Fixed film bioreactor in Iran, and finally preozonation in Taiwan. Lab scales of CAS were tested in Egypt, coagulation + Filtration + Chlorination in India, MBR in Iraq, and Photo-Fenton, Photo-Fenton + CAS in Thailand. Recently, HWWs were also treated by electrocoagulation using aluminum and iron electrodes in Iran [55]. In this study the removal of COD from HWWs was investigated in a lab scale achieving a good removal at pH 3, 30 V, and 60 min reaction time using iron electrodes.

6 Efficiency of the Adopted HWW Treatment Plants

The removal efficiencies of conventional parameters as well as PhCs from HWWs using different systems are discussed below. As previously reported, different technologies were tested for the treatment of HWWs acting as primary, secondary, and tertiary steps.

6.1 Removal Efficiency of Conventional Pollutants

Figure 1 shows the removal efficiency of conventional pollutants obtained from different studies using a primary treatment (Coagulation + filtration + disinfection; Photo Fenton) and secondary treatment (CW; Ponds; CAS; MBR; Biological contact oxidation + MBR + NaClO disinfection; Anaerobic aerobic fixed film reactor, and Aerated fixed film bioreactor + O3).

Fig. 1
figure 1

Removal efficiencies from HWW for conventional pollutants in different primary and secondary treatments. Data from [4, 17, 28,29,30, 32, 35, 38, 45, 52]

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Very good removal efficiencies were observed for TSS and BOD5 (97–99%), COD (94–97%), N–NH4 (80–99%), total coliform (99.87–99.999%), E. coli (99.98–99.999%), and Streptococcus (99.3–99.99%) using a septic tank followed by a H-SSF and a V-SSF bed purposely designed for the treatment of HWWs in Nepal [40].

The suitability of a series of facultative and maturation ponds for the treatment of HWWs has been examined in Ethiopia [32]. The percentage treatment efficiency of the pond was 94, 87, 87, 69, 55, 55, and 32 for BOD5, TSS, COD, Nitrate, Nitrite, Total Nitrogen, and Total Dissolved Solids, respectively, while the treatment efficiency for total and fecal coliform bacteria was 99.74% and 99.36%, respectively. However, the effluent still contains large numbers of these bacteria, which are unsuitable for irrigation and aquaculture.

A pilot-scale system integrated anaerobic–aerobic fixed film reactor for HWW treatment was constructed and its performance was evaluated in Iran [52]. The results show that the system efficiently removed 95, 89, and 86% of the COD, BOD, and NH4, respectively. COD removal was greater than 70% when 200 mg/L of ferric chloride was added to an Indian raw hospital effluent and removal increased to over 98% if the coagulant was added to settle HWW. A subsequent disinfection step using calcium hydrochloride reduces not only microorganisms, but also COD [17].

Attempts have been made to reduce toxicity and improve the biodegradability and oxidation degree of pollutants in HWWs prior to discharge into the existing biological treatment plant [45, 56]. Using the photo-Fenton process as a pretreatment method, a significant enhancement of biodegradability was found at the following optimum conditions: a dosage ratio of COD:H2O2:Fe (II) of 1:4:0.1 and a reaction pH of 3. At these conditions, the value of the BOD5:COD ratio increased from 0.30 in raw wastewater to 0.52 for treated wastewater. The toxicity of the wastewater drastically reduced with this process [56].

Nasr and Yazdanbakhsh [35] investigated the treatment efficiency of 70 governmental hospitals from different provinces of Iran, where 78% of them use the CAS system and 22% use septic tanks. The mean removal rates of BOD, COD, and TSS were found to be 67%, 64%, and 66%, respectively. A high removal rate (99–100%) of fecal and total coliforms was obtained using CAS and MBR, followed by disinfection treatment [4, 30].

Figure 1 clearly demonstrates how MBR technology is capable of achieving good removal efficiency (80%) of all the macro-pollutants, with the sole exception of NH3–N, whose removal was found to be 71%.

In Iraq, local wastewater treatment units in various hospitals are not capable of meeting Iraqi standards, especially in terms of nutrient and pathogen removal. For this reason, a lab scale sequencing anoxic/anaerobic membrane bioreactor system is studied to treat hospital wastewater with the aim of removing organic matter, as well as nitrogen and phosphorus under a different internal recycling time mode [38]. The system produces high quality effluents which can meet Iraqi limits for irrigation purposes for all measured parameters.

Membrane separation plays an important role in ensuring excellent and stable effluent quality. The advantages of MBR systems, such as complete solid removal from effluents, effluent disinfection, high loading rate capability, low/zero sludge production, rapid start-up, compact size, and lower energy consumption, have driven authorities to use them in treating HWWs.

An interesting approach to managing hospital effluents has been established in China, where over 50 MBR plants have been successfully built for HWW treatments, with a capacity ranging from 20 to 2,000 m3/d (see Table 4). MBR can effectively save disinfectant consumption (chlorine addition can decrease to 1.0 mg/L), shorten the reaction time (approximately 1.5 min, 2.5–5% of the conventional wastewater treatment process), and deactivate microorganisms. Higher disinfection efficacy is achieved in MBR effluents at lower doses of disinfectant with fewer disinfection by-products (DBPs). Moreover, when the capacity of MBR plants increases from 20 to 1,000 m3/d, their operating costs decrease sharply [29].

Table 4 Application of MBR in hospital wastewater treatments in China (Adopted from [29])
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The performance of a submerged hollow fiber membrane bioreactor (MBR) for the treatment of HWW was investigated by [28]. The removal efficiencies for COD, NH4+–N, and turbidity were 80%, 93%, and 83%, respectively, with the average effluent quality of COD <25 mg/L, NH4+–N <1.5 mg/L, and turbidity <3 NTU. Escherichia coli removal was over 98%. The effluent was colorless and odourless.

A combination process of biological contact oxidation, MBR, and sodium hypochlorite disinfectants has been applied to treat HWWs in Tianjin (China). The obtained results showed that the main parameters meet the requirements of the Chinese discharge standards of water pollution for medical organizations [30].

6.2 Removal Efficiency of PhCs

Figure 2 reports all collected data regarding the removal of PhCs in hospital effluents using a full scale CAS system operating in different countries (Vietnam, India, South Korea, and China). High removal efficiencies (>80%) were observed for bezafibrate, chloramphenicol, trimethoprim, aripiprazole, clozapine, fluvoxamine, olanzapine, risperidone, sulpiride, and citalopram. Albendazole, ampicillin, N4-acetylsulfamethoxazole, chlorpromazine, chlorimipramine, flubendazole, and perphenazine were moderately removed (60–80%), whereas low removal (less than 50%) was observed for alprazolam, oxazepam, sertraline, trihexyphenidyl, clozapine, fluoxetine, lorazepam, and fenbendazole.

Fig. 2
figure 2

Removal efficiencies from HWW for selected PhCs in CAS system. Data from [6, 10, 11, 42]

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Negative removals of sulfamethoxazole, chloramphenicol, erythromycin, naproxen, bezafibrate, and ampicillin in sewage treatment plants treating hospital effluents in South India were also observed [11].

The results achieved by Yuan et al. [10] showed that a secondary treatment of a psychiatric hospital was more effective in removing the majority of target compounds [e.g., olanzapine (93–98%), risperidone (72–95%), quetiapine (>73%), and aripiprazole (64–70%)] than treated municipal wastewater.

The overall removal values of ciprofloxacin and norfloxacin in a small HWWTP consisting of a CAS+ anaerobic biological treatment system situated in Vietnam were found to be 86% and 82%, respectively [6].

7 Regulation

As previously reported, HWWs are often considered similar to urban wastewater. As a result, they are usually co-treated with urban wastewater in the WWTP. Moreover, in many developing countries, they are directly discharged into the environment along with urban wastewater.

There is no regulation in most of the studied countries that imposes authorities to treat HWWs as special waste, with the exception of China where, in July 2005, the Chinese authorities published the “Discharge standard of water pollution for medical organization,” a document outlining comprehensive control requirements for HWWs [30]. Recently, a new law regarding environmental protection has been presented in Vietnam (No. 55/2014/QH13, article 72) [57]. This law obliges hospitals and medical facilities to collect and treat medical wastewater in accordance with environmental standards.

On a global scale, the only existing guidelines concerning hospital effluents management and treatment were published by the World Health Organization (WHO) in 1999: “Safe Management of Wastes from Health-Care Activities” [58] and updated in 2013 [59]. This publication describes basic methods for the treatment and disposal of health-care wastes and in particular recommends a pretreatment of effluents originated from specific departments as discussed in [60] of this book. These guidelines could be a reference in the management and treatment of HWWs mainly for developing countries in order to preserve the environment.

8 Conclusions

Hospitals are important point sources contributing to the release of both PhCs and antibiotic resistant bacteria into surface waters, especially if hospital wastewaters are discharged without treatment into the receiving ambient waters. This problem is more severe in developing countries because no wastewater treatment facility is available in most of the cases. Hospital wastewaters are subjected to different treatment scenarios in the studied countries (specific treatment, co-treatment, and direct disposal into the environment). Due to the lack of municipal wastewater treatment plants, the onsite treatment of hospital wastewater before discharge into municipal sewers should be considered a viable option and consequently implemented. Where applicable, the discharge of HWWs into municipal wastewater collection systems is an alternative for wastewater management in hospitals. Upgrading existing WWTPs and improving operation and maintenance practices through the use of experienced operators are recommended measures.

In general, there is no single practice which could be considered a solution to the problem of managing HWWs. Indeed, in many cases, a number of sequences are used in combination. Each practice has its own strengths and weaknesses. More effective disinfection processes coupled with membrane filtration should be adopted for better removal of harmful bacteria and PhCs.