Wastewater Treatment in Developing Nations

Wastewater Treatment in Developing Nations: History

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Subjects: Water Resources

Contributor:

Hemanshi D. Padariya

Water is the founding fundamental of life and hence is a basic need of life. Due to poor water quality and sanitation problems, most health issues are caused by water-borne infections. In developing countries, untreated wastewater is released into water bodies or the ground, thereby polluting natural resources. This is due to the lack of sufficient infrastructure, planning, funding, and technologies to overcome these problems. Additionally, the urbanization of megacities in developing countries is highly accelerated, but it is disproportionate to the required resources for treating wastewater.

unsustainable
urbanization
biodegradable
wastewater treatment

1. Introduction

No life form on earth can exist without water. Human civilization is dependent on water for domestic and industrial purposes. It is one of the most precious assets on this planet. The earth’s surface consists of 71% water, but only 0.3% is usable (National Ground Water Association) as shown in Figure 1. Our water demand is fulfilled from underground, rivers, wells, and streams [1]. The earth is a closed system i.e., it does not allow the transfer or exchange of any matter including water. Hence, water is a limited resource. The water that was present billions of years ago is the same that we are using now. Mother earth maintains the water quantity and quality through the hydrological cycle. This substantiates the need of reusing water for our domestic and industrial purposes. Chemically, water is a universal solvent; it is tasteless, odorless, and colorless. Owing to this nature, water leaches minerals from nature that make it more beneficial for drinking purposes [2]. But due to the same characteristic, water also dissolves natural and artificial harmful chemicals like cancer-causing metals, pesticides [3], detergents [4], and industrial wastes that may make it toxic and unusable. The quantity of such toxic matter present in water determines its quality.

Figure 1. Distribution of earth water.

The organic and inorganic matter present in water makes it an ideal medium for microbial growth. The main cause of microbial contamination in natural water resources is the discharge of waste from domestics, organizations, hospitals, industries, etc. [5]. The use of untreated water could result in the declension of the ecosystem and public health. Contaminated water can transmit diseases such as diarrhea, cholera, dysentery, typhoid, and polio. It is estimated that drinking contaminated water causes 485,000 diarrheal deaths each year (WHO) [6,7].

Water pollution is increasing due to contemporary civilization accompanied by modern industries and the booming economic system. The direct and untreated discharge of used water from urban drainage and industries into rivers is a major cause of the degradation of water quality [8,9]. This is due to either lack of awareness, inappropriate drainage system, or unavailability of wastewater treatment plants [10,11,12]. Due to unawareness, residents dump their waste products into seas, streams, rivers, ponds, and lakes thinking of water bodies as the final home of waste material. Such human activities are not only responsible for spoiling water quality, but also for affecting aquatic life [13,14]. There is an urgent need to address these problems and employ the best water treatment methods. It is a challenge for humankind to make sustainable development in civilization without damaging the environment. When water is used for domestic and industrial purposes, the used water carries deleterious constituents. According to the United Nations (UN), about 80% of sewage is currently discharged without treatment [15,16,17]. The untreated water either sinks into the ground polluting groundwater, or flows into our natural resources and contaminates them [18,19,20,21]. Water management is a global issue [22,23]. Across the globe, countries are facing problems over the insecurity of water and water contamination. But the challenge of water quality and safety is more severe in developing nations. In order to reuse water efficiently, proper waste management policies and infrastructure are quintessential. Water scarcity and sanitation are global problems; however, they are more pronounced in developing nations [21]. In 1996, food and agriculture organizations (FAO) stated that the water quality programs that are run in countries collect the wrong sample from the wrong place using the wrong substrate, at wrong sampling frequencies, and produce unreliable data and this is most commonly observed in developing countries (FAO, 1996). The water supply and sanitation, and the World Health Organization (WHO) have estimated that 25% of urban and 82% of the rural population of developing countries lack access to safe drinking water and sanitation services (CNES, 2003).

2. Sources of Wastewater

Wastewater is produced largely due to human activities. Water gets polluted from two major sources—point source (PS) and non-point source (NPS) as shown in Figure 2 [26]. When the source of pollutant is identifiable and it is released through the pipe, channels, or tunnels it is called a point source. Examples of PS are effluent released through pipes from homes, commercial areas, hospitals, wastewater treatment, and industries. Whereas, when pollutant enters the water resources via unidentifiable sources then it is known as NPS [26,27]. Examples of NPS are run-offs from agriculture, forests, mines, stormwater, etc.

Figure 2. Sources of Water Pollution.

Monitoring and regulating the non-point source of water pollution is one of the biggest challenges for the scientific community and authorities [28,29]. Dealing with the non-point source of water pollution is analogous in developing and developed countries [30]. However, it is more conspicuous in developing countries than developed countries due to the insufficient infrastructure, unplanned and unsustainable urbanization, and lack of updated technology [31,32,33]. Table 1 is showing various types of sources of water pollution.

Table 1. Sources of water pollution along with their side effects.

Sources	Pollutants along with Their Effect	References
Waste generated from agricultural run-offs	Phosphates and nitrates in fertilizers Causes eutrophication	[34]
Waste generated from agricultural run-offs	Pesticides, herbicides	[35,36]
Animal waste from farms	Microorganisms (bacteria, protozoa, and viruses) that may cause water-borne diseases	[37]
Untreated sewage (human fecal matter + domestic waste)	Suspended solids and microorganisms Suspended solids may lead to reduced sunlight penetration in lakes, ponds other water bodies affecting aquatic flora and fauna. Pathogenic microbes from carriers may cause food and water-borne diseases like cholera, typhoid, etc.	[38,39]
Industrial effluents (metal-based, dyes, rubber, etc.)	Heavy metals like As, Hg, Cu, Cd, Cr, and Ni may accumulate in aquatic organisms and enter the food chain, leading to bioaccumulation. Severe to chronic diseases caused by heavy metals.	[7,8,40,41,42]
Underground pipes	Pb Highly toxic heavy metals may cause mental disorders among children	[43,44]
Domestic waste	Detergents, surfactants, may cause foaming of water bodies leading to reduced water supply to aquatic organisms.	[4,45]

3. Composition of Wastewater

The world’s freshwater resources are becoming increasingly polluted with organic waste, pathogens, fertilizers and pesticides, heavy metals, and emerging pollutants [46]. The organic and inorganic matter released from point and non-point water polluting sources is causing a reduction in river dilution capacity [47]. Domestic wastewater is discharged from homes and communities. Domestically, water is used for washing, cleaning, and flushing. Hence, used water carries soluble and non-soluble solid material. The domestic wastewater released due to washing, laundering, bathing, or showering is called Grey Water. The Domestic wastewater released from toilets or urinals is called Black Water [48] (Environmental protection Agency, 2021). The black wastewater is rich in organic matter and mostly biodegradable, it acts like nutritional media for pathogenic microbial growth, and hence it becomes hazardous and septic [49,50,51].

Industrial wastewater is an aqueous discharge released by industries. Industries need water for manufacturing, processing, cooling, diluting, washing, or transporting the product. The used water from industries carries suspended or dissolved matter released during industrial processing [52,53,54]. The content and quality of industrial wastewater depend on the type of industry and its product [55]. The quantity of wastewater generated in many industries varies substantially from process to process and is substantially higher in developing countries [56].

The major pollution contributors are manufacturing industries like power generation, mining and construction, and food processing industries [8,45,57,58]. It may contain biodegradable [3,59], non-biodegradable [60,61], synthetic or heavy metal matter [62]. Developing countries are facing an extremely miserable situation where more than 90% of sewage waste and almost 70% of industrial raw wastes are becoming a part of the water bodies [63]. In developing countries, industrial waste disposal becomes more challenging because of the high production of wastes per unit area and the decrease in the proportion of land available for its disposal. Most industries dispose of raw effluent, which contains pathogens, heavy metals, soluble and insoluble salts, and organic and inorganic matter causing groundwater pollution [64,65,66]. Very few industries have adequate wastewater treatment facilities. As a result of this, freshwater becomes unfit for human use.

The wastewater composed of sewage; industrial, and agricultural waste is discharged globally in tens of millions of cubic meters per day. As a result, freshwater resources are polluted with fertilizers, pesticides, organic wastes, heavy metals, pathogens, agriculture waste, and emerging pollutants [57,67]. The acute poisoning of pesticides is causing morbidity and mortality, chiefly in developing countries (WWAP, 2018). The emerging pollutants are those, which have been recently identified as a danger to human health (UN, 2020). The emerging pollutants include chemicals and drugs used in modern lifestyles like cosmetic and personal care products, pharmaceuticals, hormones, endocrine disrupting chemicals, and pesticides [68,69,70].

According to reports, in developing countries untreated wastewater is discharged into rivers and water bodies, resulting in endangerment of aquatic life. The natural or synthetic pollutants, which are not commonly monitored in the environment, have the potential to invade the environment and cause a detrimental effect on human health and ecology. The European Aquatic Environment (EAE) has listed more than 700 emerging pollutants. Normal Network has categorized the emerging pollutants into more than 20 classes based on their origin. The major classes are pharmaceuticals, pesticides, disinfectants, and chemicals from various industries [71].

In developing countries, there were no studies regarding emerging pollutants due to a lack of awareness, funding, and infrastructure. As a result, the health risk associated with wastewater use is higher in developing countries. After 2005 and subsequently, research in this area was initiated, however, much more research and studies need to be conducted in developing countries [72,73]. Table 2 shows various types of pollutants and their composition, released from industries and domestic sources.

Table 2. Industrial and domestic and their effluent composition [74].

Major Sources	Source	Composition of Effluent	References
Industries	Petroleum, stainless steel, paint industries, power generation, mining, construction, and food industries.	Zinc, copper, nickel, cadmium, xylene, benzene, toluene, NORM, monocyclic aromatic hydrocarbons, chromium, lead, mercury, aluminum, radioactive molecules, platinum group metals, silver, barium, silver, arsenic, molybdenum, chloramines, radium, fluoride, nonylphenol ethoxylates (NPE), di-(2-ethylhexyl)phthalate, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzo-p-furans, nitro musks (chloronitrobenzenes), oestrogenic compounds and polyelectrolytes, etc.	[75,76,77,78]
Domestic	Kitchen and sewage.	Fertilizer and pesticides, lead and cadmium (from batteries), plastic bags, papers, polythene bags, rotten fruits and vegetables, and linear alkyl benzene sulphonates (LAS) are the major components of washing powder and found in detergents and microbes, etc.	[79,80,81]

4. Centralized and Decentralized Wastewater Treatment in Developing Countries

There are two approaches for wastewater treatment—centralized and decentralized. The centralized approach is a conventional one, where wastewater is treated at a central location and then distributed using a network of the pipeline network. The centralized system uses a combination of different processes and techniques like flocculation, coagulation, filtration, sedimentation, disinfection, etc. The techniques and processes ensure maximum removal of organic matter, pollutants, and pathogenic microbes. The major disadvantage of a centralized system is the need for huge investment in building the infrastructure and its maintenance. Decentralized wastewater treatment uses a range of simple technologies to treat wastewater from near or at the point of generation, for example, individual homes, colonies, institutes, or industries. Considering the problem of non-point source water pollution, decentralized wastewater treatment seems to be a logical and sustainable option. According to [145], a centralized wastewater treatment plant is more expensive than a decentralized one. The major differences between centralized and decentralized are shown in Table 4.

Table 4. Centralized vs. decentralized Source—[146].

Centralized	Decentralized
Definition.	The wastewater is collected and treated at a central location and then distributed using a network of a pipeline network.	Decentralized wastewater treatment is the use of a range of simple technologies to treat wastewater from near or at the point of generation.
Also called:	Off-site Treatment.	On-site Treatment.
Huge network of pipeline, excavation, manholes.	Required.	Not required.
Length and diameter of pipes.	Large and long.	Small and Short.
Waste is collected from	From long distance.	Near or at the site of a pollution source.
Composition of collected wastewater	A mixture of black, grey, and industrial water.	The type of water is separated from the source.
Owned by	State Authority
Scale of operation	Large.	Small.
Area required	A huge area is required in a central place.	A small area is required at the site of the pollution source.
Investment	Huge investment is required.	Comparatively less and it is cost-effective.
Technical Staff	Dedicated staff are required for maintenance	Can be maintained fortuitously.
Preferred for	High population density region	Low population density region.
Affordability	People of developed countries can afford.	People in developing countries cannot afford.
Technology used	Combination of different advanced types of technologies	Primitive technology like septic tank/drain field.
A consequence of improper maintenance	Detrimental health issues at the regional level	Detrimental health issues in local areas.

Laugesen et al. (2010), have predicted that “despite the past failures of most centralized systems, it is likely that most new wastewater management systems in developing countries will continue to be advanced, centralized, and with a continued high probability for failure” [147]. UNESCO, and UN-Water (2017), have alarmed such countries about the risky investment in the centralized system due to inadequate finance and institutional capacity. As per USEPA research, decentralized wastewater management is more appropriate for developing countries due to its cost-effectiveness [145]. The lack of awareness, education, and research in such countries failed to select the appropriate approach for wastewater treatment. They also fail to consider the geographical conditions, human resources, cultural aspects, and finance.

In 2018, Zinn and his coworkers reviewed different technologies used for wastewater treatment in developing countries. They enlisted technologies, namely solar water disinfection (SODIS), chlorination, ceramic and bio-sand water filtration, and slow sand filtration. They compared the strength and weaknesses of these technologies, and also mentioned the pathogenic bacteria that the respective technology eliminates. They also found that SODIS is a more efficient technology than others, but hypothesized that in the future, membrane filtration will be preferred. The authors have also compared the effectiveness, advantages, and disadvantages of these technologies.

In India, the new wastewater treatment technology is a combination of electrocoagulation and electroflotation [148]. Electrocoagulation uses an electrical charge to change the surface charge of the particles due to which the particles become aggregated. In electro flotation, the suspended particles are removed by passing electricity through water generating hydrogen and oxygen [149]. In African countries, technologies like sludge deactivation, trickling filter, oxidation ditch, and aerated lagoons treat the wastewater [150,151]. China has come up with electron beam technology to treat industrial and medical wastewater. China has started the World’s largest wastewater treatment facility [152]. In Turkey, technologies like UV disinfection, sand filter, chlorination, rapid sand filter, disc filter, membrane bioreactor, activate carbon, ultrafiltration, ozone disinfection, and cartridge filters are used. Turkey is facing technical, social, and economical barriers to reusing wastewater [153].

This entry is adapted from the peer-reviewed paper 10.3390/w14162537

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