Environmental Degradation: Monitoring, Assessment and Treatment Technologies

The rapid growth of industrialisation has shown adverse effects on the environment. Industrial wastes are one of the key sources of pollutants. Therefore, the treatment of industrial effluents before discharging into sewage lines has become a matter of great concern for environmental conservation (Sarker et al., 2016). In Bangladesh, 10% of industries with more than 3000 industrial units have their own effluent treatment plant while the remaining industries discharge effluents in the river without any treatment/with minimal treatment, which contaminates ground water, agricultural lands, irrigation system and are finally introduced into the food chain by getting transferred into various plant parts through soil (Roy et al., 2014).

The populace in urban boundaries is expanding exponentially. Water is one of the foremost basic needs of each living substance. These days, the disposal of untreated wastewater has become one of the major concerns for society. Since numerous civic organizations in India still do not have a wastewater treatment office, they specifically dispose wastewater into neighbourhood water bodies or streams, which in due course of time meets the primary waterways and contaminates them. Since ordinary sewage treatment strategies are expensive and require gifted labour for their operation and upkeep, many small metropolitan enterprises do not focus on sewage treatment. As per the CPHEEO manual, roughly 70% to 80% of residential water gets released as wastewater. There is a critical crevice between wastewater generation and installed wastewater treatment plant capacity. According to the CPCB 2009 reports, urban ranges are producing 35254 MLD sewage whereas treatment offices can access only 11777 MLD. Within the reply to the Lok Sabha address (2016) given by Service of Environment and Woodland, the Government of India uncovered that total wastewater generation from urban ranges within the nation has developed up to 61948 MLD and its accessible introduced treatment capacity is 23277 MLD only. As per (CPCB, 2016) reports a total of 920 numbers STPs are working to treat wastewater. There is a massive difference between era and wastewater treatment frameworks and the number of STPs required to fill these gaps by choosing suitable treatment techniques.

Textile effluents highly pollute the fresh (surface) water bodies because of the presence of various toxic dyes. During the dyeing process, around 20-50 % of the dyes end up in the water phase and cause severe problems to the environment (Yurtsever et al., 2017). Also, the presence of dyes creates an undesirable aesthetic impact in receiving water bodies (Guimarães et al., 2012). Hence, the proper removal of dyes is necessary before they discharge into the environment.

The water crisis and its scarcity have pushed countries, especially the energy-rich countries, during the large part of the year, to exploit resources that are not sufficiently replaced. Also, waste water from agricultural and residential areas contains high levels of nutrients and if this water is not treated, it could contaminate surface water and groundwater systems, thereby restricting the availability of water for other uses (Sarafraz et al., 2009).

In ancient countries like India, every development is pioneered around the water bodies. India homes for a few hundreds of lakes which accounts for both natural and artificial lakes that are considered an important part of the ecological as well as religious cycle. Over the past century, there is a prodigious increase in human settlements, anthropogenic pressure and public effluent sources around the lakefront resulting in the degradation of the lake in both aspects of quality and quantity. Practicing appropriate remediation techniques can improve a lake’s water quality, so there is a definite need for continuous monitoring of a lake (Yadav et al., 2014). The arduous and tedious task of assessing the lake water quality based upon individual parameters (Hou et al., 2016) is evaded by practicing different approaches like statistical approaches, water quality indices, etc (Guo et al., 2018.). Over the past two decades, WQI is on a positive gradient of importance in assessing the surface water quality of the lake and river bodies (Kachroud et al., 2019). The main objective of WQI is to provide a score of water quality by aggregating different physical, chemical and biological parameters. The history of WQI dates back to 1965 as studied by Horton et al. (1965). Since then there has been the development of various new indexes by using some computational methods like fuzzy techniques, neural networks techniques, Prime-component analysis, etc. The sequential framework for the development of a WQI is shown in Fig. 5.1.

Distillery wastewater (spent wash) is one of the highly polluted wastewater generated from alcohol distilleries. In India, there are around 319 distilleries, producing about 40 thousand million litres of wastewater annually (Pant and Adholeya, 2007). Ministry of Environment, Forestry and Climate Change (MOEF & CC) has categorised alcohol distilleries among the top positions in the “Red Category Industry” list (Tewari et al., 2007). A huge amount of high strength wastewater is generated by this industry every day as a spent wash, spent lees and fermenter sludge. Approximately 8-15 L of the spent wash is generated for every 1 L of alcohol produced by a conventional distillery industry (Sankaran et al., 2014). Distillery wastewater is recalcitrant in nature having a dark brown colour with high organic (biological oxygen demand and chemical oxygen demand) and inorganic (sulphates, potassium, phosphates, and nitrogen) load (Sankaran and Premlatha, 2018). Melanoidins present in the distillery wastewater imparts a brown colour to this wastewater and are formed due to Maillard amino carbonyl condensation reaction. Due to the antioxidant properties of melanoidins, these compounds are typically not degraded by micro-organisms present in the wastewater treatment process and are also toxic to those micro-organisms. This resistant nature of melanoidins makes a clear route for their entrance into the environment even after various stages of treatments (Singh et al., 2018). When such a high strength untreated or partially treated distillery wastewater enters into the environment, it leads to serious environmental threats such as eutrophication of water bodies and loss of soil fertility (Chowdhary et al., 2018).

Water is one of the most essential but limited commodities on this Earth. Water covers around 70% of Earth’s surface. Where only 3% of water resources belong to fresh water category i.e. ground water, fresh lakes, rivers, polar ice, and glaciers. But a very small proportion of fresh water can be used for drinking purposes which consists of less than 1% of fresh water resources. Hence, water resources need to be maintained properly and the recycling of waste water needs to be taken into account seriously. Fast population hike, agriculture, industries and domestic wastes result in an increasing amount of pollutants. An exponential increase in pollution affects the water quality day by day. Moreover, these wastes and pollutants contribute high content of micronutrient leaching, especially phosphate in water commodities. Phosphate has been considered as a major micro nutrient for all living microbial communities for diverse physiological purposes. These major physiological processes include cellular maintenance, nucleic acid biosynthesis, cellular membrane construction (phospholipids biosynthesis) and chemical energy harness reactions (i.e. ATP synthesis) by White and Metcalf (2007). But it becomes a pollutant if its concentration is more than the threshold recommended limit. Current investigation shows that normal phosphate content ranges from 0.021 mg/litre to 0.071 mg/litre. There is no confined Bureau of India Standards (BIS) standard permissible limit for phosphate for potable water, but World Health Organization (WHO) has fixed it to be 0.1 mg/litre in its 1993 convention. Moreover, the Environmental Protection Agency (EPA) has recommended that the threshold phosphates level in drinking water needs to be around 5 mg/liter though beyond the permissible limit it may cause human health hazards most likely kidney damage and osteoporosis (Slatopolsky et al., 1971).

With the advent of the industrial revolution, the use of chemical substances has progressively increased. It includes metals, non-metals, and organic as well as inorganic substances. Few metal ions get promulgated into nature due to activities like biological, geological and human activities. The word ‘textile’ origin from the Latin word ‘texere’ means to weave. As we know textiles are the largest waste water producing industries among all. To produce a single textile it further goes into several mechanical processing stages like knitting, spinning, weaving, garment production, etc. with few wet processes like dying, sizing, bleaching, desizing, mercerizing, printing, etc.

The rapid growth of population has led to intense urbanisation in the city of Guwahati, which has caused the water bodies in the city to deteriorate (both quality as well as quantity wise) to a substantial extent (Das et al., 2003). Deepor Beel (a Ramsar site) is one such water body that has been continuously degraded owing to a sudden increase in the urban built-up of Guwahati city (Dash et al., 2018). Assessment of the water quality of a particular water body requires continuous monitoring and analyses of several parameters. This, in turn, contributes to the development of large and complex water quality datasets that are difficult to interpret. Traditionally, the water quality of a particular water body was assessed by comparing the observed values of some water quality parameters with their corresponding quality standard values (Pesce and Wunderlin, 2000). This, however, makes the sustainable management of water resources very challenging and sophisticated, as well as time-consuming (Sun et al., 2016; Wang et al., 2015). Quality indices have proved to be of immense help to water quality researchers around the globe for the past few decades. This is owed to their extreme simplicity of dataset interpretation. Water quality index (WQI) is a mathematical representation of the datasets for categorising the water quality in a more straightforward yet informative manner, thus assessing the pollution status of a particular water body. Numerous attempts have been carried out in developing WQIs, depending on various methodologies adopted by several researchers (Akter et al., 2016; Bora and Goswami, 2017; Liou et al., 2004; Ramakrishnaiah et al., 2009; Said et al., 2004; Şener et al., 2017; Vasanthavigar et al., 2010; Wu et al., 2018). It has been proved over the years that the WQI approach is the most practical and effective way of water quality representation of a particular waterbody, both spatially and temporally. It also facilitates in comparing various sampling locations based on their pollution levels and determining their trends (Sun et al., 2016).

Water is the primary necessity of every living being. But for better livelihood, human beings doing numerous activities such as industrialization, urbanization, etc. lead to polluting surface water sources. The wastewater contains various pollutants like dye, pharmaceuticals, pesticides, surfactants, etc. (Garcia-Segura et al., 2016). A dye is a common pollutant that is harmful, toxic and carcinogenic in nature coming in the effluents of various industries like textile, paper, paint, food, leather, hair colouring cosmetics and printing industries. Eosin yellow (EY) is one of the synthetic dyes based on disodium salt (Rani et al., 2020). Discharge of effluent carrying EY dye will create environmental issues by increasing chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in the water source. Also, coloured water inhibits the penetration of sunlight into the water body, so it affects the photosynthesis process of aquatic plants. This phenomenon results in a decrease in dissolved oxygen (DO) level in the water body which also affects the respiration process of aquatic animals (Kumar and Ghosh, 2019; Tarkwa et al., 2019). Being carcinogenic and mutagenic in nature, it also affects human health. So, there is a strong need for treatment before it is released into any surface water stream.

The leaching of heavy metals in the environment has gathered attention after toxic impact on the ecosystem and humans (Singh et al., 2009). This research focuses on hexavalent chromium Cr(VI), well-known for its toxicity. Chromium hexavalent Cr(VI) reports human toxicities such as lung cancer, kidney, liver, and gastric damages (Aroua and Zuki, 2007). Consequently, concentrations of chromium compounds need to minimize including their toxicity (Pandey and Mishra, 2011). In industries, chromium compounds are used, discard chromium ions through effluent (El-Taweel et al., 2015). Industrial effluents containing chromium compounds are treated applying tailored methods. Mostly, two stage batch process, which alters Cr(VI) to Cr(III) by adding sodium meta bisulphite in acidic pH, followed by precipitation of Cr(VI) to Cr(OH)₃ in the alkaline phase (Bhatti et al., 2011). Furthermore, Cr(VI) can be minimised by applying coagulation and flocculation (Haydar and Aziz, 2009), membrane (Pazouki and Moheb, 2011), adsorption (Jung et al., 2013), ultrafiltration (Aroua and Zuki, 2007), ion-exchange (Cavaco et al., 2007), nanomaterials (Wang et al., 2010) and microbial fuel cell (Wang et al., 2008). The techniques listed have some demerits over efficient removal of Cr(VI) from effluents as received during the process. Recently, the electrochemical process has attracted huge attention after its versatility and environmental compatibility (Barrera-Díaza et al., 2012), offering an alternative for conventional treatment methods (Benhadji et al., 2011). Electrocoagulation (EC) process has merits, such as lower sludge volume, low chemical and easy to operate (Chou et al., 2009). This paper aims to assess the performance of the electrocoagulation process to remove Cr(VI) from simulated wastewaters. This study enumerates the effect of operational parameters (current density, initial pH, electrode material (anode and cathode), the surface area of the electrode and bipolar material (iron, aluminium, graphite)) linking them to improve Cr(VI) removal at lower energy and material consumption. In addition, the experiment also describes kinetics and adsorption isotherm involved to diminish Cr(VI) related to the electrocoagulation process.

The expansive growth of dairy industries in India over the years has achieved annual milk production of 165 million tons (FAO, 2018). As the dairy sector keeps contributing to the national economy, it becomes crucial to devise steps for its proper management. Most of the processes in dairy plants include the milk receiving section, curd section, paneer section, lassi and buttermilk section and packaging section (IS:8682-1977: Reaffirmed, 2003); these processes require a huge amount of water; subsequently, resulting in the generation of a huge quantity of dairy wastewater. It contains a large amount of organic matter, if disposed of untreated, causes water pollution by rapidly depleting the dissolved oxygen, which threatens the aquatic life. To avoid such adverse effects on the environment, a suitable dairy wastewater treatment process needs to be devised and adopted as well.

Greywater utilisation post-treatment is an essential strategy for the conservation of freshwater. It comprises different water pollutants, including organics and nutrients, originates from several household water-usage activities such as hand washing, bathing, cleaning clothes, utensils, etc. The discharge of greywater directly into the ecosystem and soil can drastically affect the aquatic species in the lake due to eutrophication and negative effects in the soil properties, respectively. Due to this reason, several conventional treatment methods were studied, such as filtration unit using ceramic wastes (Mohamed et al., 2018), and slanted soil system (Ushijima et al., 2013) to remove total suspended solids and organics from greywater. These systems are prone to clogging issues and can have high installation and maintenance costs.

The pharmaceutical industry is responsible for the development, production and marketing of various types of medications to help treat a wide variety of diseases of both humans and animals. Despite being under many regulations, there are growing concerns regarding the impact of pharmaceuticals on the environment. Recently, three pharmaceuticals along with eight synthetic hormones, pesticides and other pharmaceutical by-products have been listed as contaminants in Contaminant Candidate List (CCL-3) by United States Environmental Protection Agency (USEPA) (Richardson and Ternes, 2018). The advancement in new techniques and analytical methods have been able to detect these contaminants to a concentration as low as few ng/L in environmental samples (Richardson and Ternes, 2018). These concerns made way to widespread and extensive research on the environmental effects of pharmaceuticals over the last couple of decades. Pharmaceuticals find their way into the environment, especially through water bodies that are fed by various sources like households, pharmacies, hospitals and manufacturers (Ziylan and Ince, 2011). Other indirect sources of these pharmaceuticals include animal farming which releases veterinary pharmaceuticals, leaching and runoff from agricultural fields (Khetan and Collins, 2007). Many active pharmaceutical ingredients in the human body which have been converted either incompletely or completely to metabolites soluble in water or, sometimes without even being metabolised are given out biologically in the form of urine or fecal matter also find their way into the WWTPs through the sewage system.

The coal mining industry is associated with several environmental issues, among which the most serious is the threat posed by the generation of acid mine drainage (AMD). The complete prevention of AMD in coal mining sites is inevitable, and thus treatment becomes necessary owing to the nature of AMD generated (Kefeni et al., 2017). AMD is generally characterised by acidic pH, low organics, high electrical conductivity (EC), sulphate-rich and high concentrations of dissolved metal ions depending on the nature of bedrock or geological strata of a mining site. The untreated discharge of AMD containing heavy metals leads to plants and animal toxicity via bioaccumulation, due to its non-biodegradable nature (Singh and Prasad, 2015; Qing et al., 2015).

3,5-Dichloroaniline (3,5-DCA) is an intermediate compound in manufacturing fungicide and pharmaceutical compounds. It can also be used for synthetic herbicides, plant growth regulators and is used to produce other chemicals. The chemical structure of 3,5-DCA is shown in Fig. 16.1 and is highly toxic to aquatic life.

Groundwater sources are getting contaminated as a result of various natural processes and anthropogenic activities, which have been a key environmental concern globally due to its direct impact on the health and environment (Machiwal and Jha, 2015; Hajigholizadeh and Melesse, 2017; Kotoky et al., 2017). This calls for an effective management programme including groundwater quality assessment and mapping that takes into account constant monitoring of the entire groundwater resource, thereby providing unswerving information about the intrinsic possessions of groundwater and its quality (Singh et al., 2004; Hajigholizadeh and Melesse, 2017).

A constructed wetland is a complex set up of majorly four components that are wastewater, substrate, vegetation, and microorganisms. Plants play an essential job in this complex set up as it gives surfaces and a reasonable situation aimed at bacteriological development and purification. During the entry of the wastewater through an even subsurface stream wetland, it is a contact of vigorous, anoxic, and anaerobic zones systems. The part of wastewater is purified by the natural reduction process by physical and chemical means (Cooper et al., 1996). Horizontal flow (HF) type CW can actively remove the organic pollutants from the wastewater. The amount of oxygen transfer in the complex set up is limited; however, HF wetlands remove the nitrates from the wastewater. The phosphorus removal in the constructed wetlands occurs in the six stages (Watson et al., 1989).

The north-eastern region of India is abundant in water supplies and is blessed with a network of rivers and lakes. Over the last decade, the rapid growth of the population, with the urbanization and industrialization of this part of the world, has raised the demand for water while, at the same time, degrading the quality of water. Almost all Indian rivers are polluted due to the discharge of untreated or partially treated sewage and industrial effluents and North-East is not an exception. Wastewater from industries are discharged into the rivers and estuaries, due to which various nutrients and toxic chemicals are added, which lead to deterioration of water resources and raise an environmental concern for the usability of such water resources. (Singh et al., 2005).

Freshwater is indispensable for industry, agriculture and even human existence (Iscen et al., 2008; Singh et al., 2017). With the population explosion and rapid industrialisation, there are continuous adverse effects on the sources of water and quality is deteriorating day by day (Singh et al., 2019a). Polluted and un-potable water is creating many health hazards to living beings and often causes many water borne diseases. Adulteration of surface waters with metal discharges from various industrial activities and domestic sewage is long standing phenomenon (Singh et al., 2019b). Again, nonpoint sources of contamination are difficult to identify and control and are one of the main reasons why urban rivers fail to reach the water quality objectives set for them. Consequently, the monitoring of water bodies and evaluation of water quality has become a critical issue (Singh et al., 2019a). Monitoring programmes evaluate a broad range of water quality parameters. The output of such programs often leads to the generation of a large amount of data sets (Dixon and Chiswell, 1996). This requires their assimilation into simple numeric scores which can be easily understood by the policy makers and the general public.

The rapid growth in the industrial sector has contributed to the deterioration of geo-environment due to the bulk generation of industrial by-products (Gomes et al., 2016; Mukiza et al., 2019). Bauxite residue (red mud-RM) is a major industrial by-product produced while alumina is been extracted from bauxite ore by the Bayer process (Kuntikana and Singh, 2017; Xue et al., 2019). Red mud is highly hazardous due to its acute and chronic pH (pH 10~13), contaminating the adjacent soil, and water bodies (Kuntikana and Singh, 2017). Moreover, the presence of heavy metals makes them unsuitable to be stored in conventionally adopted red mud pond or direct disposal to soil, river or sea (Alam et al., 2018). More importantly, the production of red mud accounts for around 150 Mt per year across the world (Xue et al. 2019). Under these circumstances, quick solutions to remediate, or establish a vegetation cover in red mud disposal area (Tayibi et al., 2009; Kuntikana and Singh, 2017) turn out to be tedious. At present, nearly 2–3% of total red mud produced per year is utilized or recycled in agriculture, as an ingredient in cement, concrete, etc. and the rest are either stored in red mud pond with low solid content (15–40%) or stored in dry solid form (~65%) (Alam et al., 2018). As a result, more than 4.5 billion tons of RM is accumulated globally (in 2019) due to the difficulty in disposal and recycling, consuming vast land area (Kong et al., 2018; Xue et al., 2019).

Rapid urbanisation has significantly changed the physical size of the cities and land requirement for human habitation; this is also exerting significant pressure on the infrastructural services across Indian cities. India currently has 53 metropolitan cities, which is likely to increase to 87 by the year 2031 (Mani and Singh, 2015). Increasing incomes, fast growing but altering lifestyles and unplanned urbanisation resulted in added quantities and change in the composition of solid waste in India. By 2031, the waste generation in terms of volume is expected to rise from 64-72 million tonnes to 125 million tonnes (Sambyal and Agarwal, 2018).

Globally, pulp and paper industry is an important industry, thus, creating lots of job opportunities; it also has a great impact on the country’s economy and growth. However, there is a great concern regarding various environmental issues created from pulp and paper mill wastewater. The pulp and paper mill consumes large amounts of water and different chemicals during various stages of pulp and paper production. In the process, it also produces a huge amount of wastewater, which has high colour, BOD, COD and potentially toxic chlorinated compounds. The effluents are often characterized by suspended solids, tannins, resin acids, phenolics heavy metals and sulphur compounds along with high lignins (Haq et al., 2016a). The industries are mostly using chlorine compounds in their sequential bleaching process. Lignin and chlorinated phenols are the major persistent organic pollutants consistently present in pulp and paper mill effluents, which contribute to colour and toxicity. Due to the complex and toxic nature of pulp and paper mill wastewater, their complete degradation is not easy through conventional techniques such as the activated sludge process or aerated lagoon. Many components of wastewater like lignin and chlorinated organic compounds are not removed entirely due to their toxicity and low biodegradability. In most cases, this effluent (raw or treated) is discharged into the rivers, streams or other water bodies causing serious problems to the receiving aquatic system as well as the community and environment. In the aquatic system, it blocks photosynthesis; as a result, it decreases the dissolved oxygen (DO) level and adversely affects flora and fauna. Accumulation of toxic pollutants and metals has occurred in the contaminated soil. The chlorinated compounds are highly toxic which is also responsible for causing carcinogenic, clastogenic, mutagenic and endocrine effects. Various studies have confirmed the toxic effects of pulp and paper mill effluents in living organisms (Pokhrel and Viraraghavan, 2004; Haq et al., 2016a, b; Haq and Raj, 2019, 2020; Haq et al., 2020; Kumar et al., 2017a, b, c). Therefore, in the present study, we aim to characterise the pulp and paper mill wastewater by various physicochemical parameters before and after secondary treatment at the industrial level. The toxicity analysis was carried out to estimate the toxic effects of pulp and paper mill effluent.