Wastewater Management Through Aquaculture

Healthy soils are of the utmost importance to society for the variety of ecosystem services they provide in both terrestrial and aquatic systems. Within aquatic systems, soils play an active role in carbon cycling and interactions between soils and water, and additional components of aquatic ecosystems can control the balance of carbon, whether the system becomes a net carbon source or sink. Understanding the interactions between soils and overlying water is crucial to developing adaptive strategies to mitigate climate change. An enhanced, holistic understanding of primary ecosystem drivers in mixed aquatic and soil systems is paramount for guiding their future construction and management to maximize their beneficial use while minimizing negative environmental impacts. Aeration and water circulation devices can be used to improve dissolved oxygen content of the wastewater pond system. Raking may be practiced to improve the ecological conditions of pond soils for encouraging healthy conditions and animal associations of the pond bottom particularly in wastewater-fed systems. The present chapter provides a review of different aspects of soil-water interactions and strategies to maintain ecosystem health for sustainable development.

Wastewater generated from different sources creates environmental problems after entering the aquatic ecosystem due to its heavy organic load and other undesirable toxicants. As a consequence, biological and chemical oxygen demand increases with depletion of oxygen level of water; all the biotic organisms suffer from stress-related symptoms often reaching to lethal limits. However, wastewater may become a useful resource for various economic-driven activities. Wastewater reuse is primarily dependent on the microbial degradation of different nutrients present in sewage. Thus, biogeochemical cycling bacteria have profound role on the decomposition, degradation and regeneration of nutrients from organic sewage water. Thus, the metabolism and turnover of the whole sewage-fed ponds are regulated by nutrient cycling and energy flow in the trophic level. Waste stabilization pond has been recognized as effective treatment system with removal of as high as 90–95% dissolved organic matter and reducing pathogens through microbial activities under aerobic and anaerobic conditions in trickling filter, activated sludge processes, etc. Interactions within and between carbon, nitrogen and phosphorus pools in nutrient cycles of wastewater-fed ponds ultimately result in nutrient removal from wastewater. A series of waste stabilization ponds (anaerobic, facultative and maturation) in which the detritus food chain is dominant over the grazing food chain is popular. It is evident that microbial activities play a crucial role in nutrient recovery from wastewater through microbial degradation of organic load leading to increased biological production while accelerating the enhancement of water quality through microbial-driven ecological processes.

Given the parlous provision of basic sanitation and wastewater treatment globally, the rationale for safe wastewater reuse through aquaculture is presented. Wastewater-fed aquaculture-related responses to counteract negative driving forces, pressures and impacts associated with inadequate sanitation and wastewater treatment and to enhance the state of systems are systematically reviewed with the DPSIR framework. Prospects for a rational design-based approach to safe wastewater reuse using treatment lagoons are discussed. A SWOT (Strengths, Weaknesses, Opportunities and Threats) assessment is presented concerning the future development of safe wastewater reuse through aquaculture. Specific opportunities for value addition to products through cutting-edge biorefinery approaches are reviewed, and the need for appropriate hazard barriers is highlighted. Conditions required to support and promote safe wastewater-fed aquaculture are assessed using the STEPS (Social, Technical, Environmental, Political/Institutional and Sustainability) framework. It is concluded that reuse using intermediaries and biorefinery approaches holds great promise. Widespread adoption of wastewater reuse through aquaculture could contribute to achieving targets specified for sanitation and safe wastewater reuse by 2030 in accordance with the United Nations’ Sustainable Development Goals.

Importance of nutrient harvesting from liquid wastes through aquaculture production in vertically integrated systems is well established. Though wastewater reuse systems in aquaculture widely differ with respect to degree of pretreatment and its methods which have a direct bearing upon the economic conditions of the end users, the ecological and socio-economic impact analyses exhibited overall positivity. Supremacy of heterotrophic microbial pathway coupled with high fish yield at downstream of the wastewater-fed system testifies the ecological efficiency of wastewater in the conversion of wastes to wealth through aquaculture. Urbanization pressure, improved economic condition and betterment in the health quality standards warranted imposition of different safety standards in wastewater aquaculture and quality of the produce with respect to pathogenic load and contaminants. The present paper discussed the waste systems in aquaculture and their analyses in general.

Freshwater is indispensable for sustenance of life on earth, but is rapidly becoming a scarce resource. A centre on wastewater aquaculture was established during the 1970s in Rahara, Kolkata, which initiated research on recycling of sewage water for production of fish through nutrient recovery. Huge volume of sewage water has been treated through different convenient modes and monitored for probable hazards of sewage water before its utilization in aquaculture. Both chemical and biological contaminants were reduced by 80% by different treatment methods. Using specialized farming management protocols through a series of culture trials, it was possible to achieve the fish yield to the tune of around 5.0 t/ha/year. Different aspects of farming such as species selection, stocking density, species ratio, choice of species groups, stocking and harvesting relation and postharvest techniques were considered. Following the WHO guidelines of risk involved in sewage-fed aquaculture, different parameters such as microbial loads, heavy metals and herbicides after sewage intake were analysed and found below safe limits. Using bioassay trials, the impact of sewage with different sewage dilutions has been optimized. Health and hygiene of handlers were critically assessed, but no adverse impacts have been observed. Sewage-fed aquaculture has great potential to develop into an effective alternate system of fish production in the backdrop of freshwater scarcity and increased farm income, though consistent monitoring is entailed from the health and hygiene perspectives.

East Kolkata Wetlands (EKW) have been recognized internationally as an important Ramsar Site with its long history of metamorphosis from saltwater area to freshwater aquaculture system fed with wastewater. It has been rendering livelihood opportunity to a large number of people in and around Kolkata through production of cheap protein source of food fish. This large-scale wetland system is utilized for wastewater treatment cum fish farming. The chapter attempts to focus important facts relating to wastewater-fed aquaculture, along with unique features that characterize such wetlands sustainable over the times. Nevertheless, this wetland system is now facing concerns which need to be resolved for benefits of fish farmers and fish consumer as well. Some measures have been addressed for sustainable management of the wetland system that would provide ecosystem service to cater the benefit of protein food production for present and future generations.

Water quality and biological factors strongly affect the growth of fish in aquaculture ponds. Deterioration of water quality and adverse biological factors, regardless of the nature of aquaculture ponds, would cause poor ecosystem health and disease occurrence in the cultured fishes. Wastewater-fed aquaculture is a well-established climate-resilient practice that contributes substantially to inland fish production in India and elsewhere. Enhancement of fish production in such systems is, however, limited by suboptimal conditions of water quality and disease occurrences. Investigations in wastewater fish culture wetlands revealed various stressors that affect fish growth and production. These stressors are (1) suboptimal diurnal as well as seasonal water quality with DO level fluctuating from 0 to 18.0 mg/l, high CO₂ (nil–16.0 mg/l), high unionized ammonia (0.11–0.42 mg/l) and low transparency (<14 cm) throughout the culture period and (2) biological stressors manifested by the abundance of urceolariid ciliates (Trichodina, Tripartiella spp.) in the hyper-mucus-secreting fish gills. The stress caused by the multiple stressors are physiologically manifested in the resident fish populations by significant changes in the levels of stress-sensitive blood parameters such as haematocrit, plasma cortisol, cholesterol, glucose, chloride and lactic acid levelss. Morphological alterations are exhibited in the form of hyperplasia, hypertrophy and oedema in the gills, proliferation of mucous cells and decrease in chromatophores in fish skin. These factors affect the growth of fish as reflected by the reduced condition factor. Stressed fish in such systems become prone to various infectious and noninfectious diseases such as fin and tail rot, dropsy, bacterial gill disease, saprolegniasis, trichodiniasis, myxosporean diseases, dactylogyrosis, argulosis, ergasilosis, hypoxia and algal toxicosis. Rapid assessment of the fish health needs to be conducted using the health assessment index (HAI) method and necessary remedial measures be adopted.

Municipal wastewater poses a win-win strategy toward environmental protection as well as for water conservation through its reuse in various economic-driven activities. Wastewater reuse reduces the demand for conventional freshwater resources and provide enormous nutrients for biological production. Sewage sludge is also well recognized for its special role in soil conservation and enhances soil fertility and helps soil loss through erosion. Safe reuse of wastewater has thus become inevitable. Sewage effluent and sludge must be treated and managed properly to avoid any adverse impacts on the environment and human health. Though conventional sewage treatment plants and recently developed bioreactors are used to treat municipal sewage for improvement of water quality for reuse, the waste stabilization pond (WSP) system has gained considerable importance as an integral tool for treating wastewater as well as for closing the loop between sanitation-driven nutrient source and culture of fish and vegetable crops in aquaponics. The concept of engineered resilient ecosystem is being applied to reclaim the partially treated municipal wastewater for ecosystem service. Macrophytes, microalgae, probiotics, annelids, mollusks, crustaceans, fishes, etc. have been rightly designated as living machines due to their immense beneficial biofilter potentials for reclamation of eutrophicated water bodies, heavy metal-contaminated perturbed aquatic systems, etc. Wise use of ecological principle, traditional knowledge, right selection of biodiversity, design of sustainable ecosystem, appropriate eco-technology, and patience for development are required where all aspects of technological, economical, legal, social, environmental, public health, and institutional are considered. A successful wastewater management decision requires a comprehensive, impartial evaluation of centralized and decentralized treatment systems.

Inland waterbodies are environmentally impacted with the wastes generated through industries and domestic sewage resulting in pollution and complex ecosystem changes. Sustainable green technology has been emerging as an important tool for remediation of perturbed waterbodies as well as wastewater-fed aquaculture ponds. Various methods for bioremediation such as biostimulation, bioaugmentation, plant-based-assisted bioremediation, phytoremediation, biofilm-/periphyton-based bioremediation, biofloc technology, biodegradation, biotransformation, nano(bio)-remediation, enzymatic bioremediation/recombinant DNA technology, biosorption and nutriremediation for alleviation of the contamination in waterbodies have been discussed. In addition, improved technology interventions in terms of abiotic and biotic stress management, environmental enhancement, stock enhancement/replenishment, species enhancement/selection of the right species, environmentally sound enclosure culture technologies, management enhancement and integrated multi-trophic aquaculture have been explored.

Municipal wastewater generated by household activities is a storehouse of fertilizers often causing eutrophication of aquatic systems and environmental degradation if not properly managed. Aquaponics is a green and sustainable eco-technological approach integrating aquaculture in hydroponic system and can play a pivotal role in harnessing nutrient from wastewater resources. Consequently, the nutrient-rich wastewater may be reclaimed with concurrent production of fish crops and economically important aquatic plants that can fetch high income from wastewater. The present chapter deals with the potentials of aquaponics in turning wastewater into suitable water for producing fish and different crops for food and nutritional security as well as environmental sustainability.

There is an unprecedented increase in per capita use of, especially water, during the past few decades. In view of the vital significance of water resources, unsustainable use of water resources would cause serious impediment to the growth of economy and standard of living worldwide. Therefore, new approaches for a sustainable utilization of water resources are of utmost importance for a secure future. In recent past, a number of new wastewater treatment technologies have been developed which paved the way for achieving the sustainability through judicious water resource utilization and management. The new wastewater treatment technology, especially the integration of urban water and waste management systems, is a promising approach for the improvement of sustainability of global water resources.

The presence of various inorganic and organic pollutants in aquatic streams has readily increased as a result of industrialization and urbanization. Among the technologies available, adsorption has widely been used for the removal of various contaminants from aqueous media, and accordingly different adsorbents have already been prepared over the years. The choice of adsorbent for purification of a specific type of wastewater containing specific pollutants is mainly determined by the concentration and type of the pollutant(s) present in the wastewater, the efficiency/cost ratio of the adsorbents and the adsorption capacity of the adsorbent for the specific pollutant(s) of interest. In recent years, researchers have focused their efforts on the use of various low-cost biosorbents and also some synthesized polymer-based adsorbents for removal of heavy metal ions from wastewater. The purpose of this article is to provide comprehensive, up-to-date and critical information on the adsorption of different heavy metal pollutants by various types of biosorbents and polymer-based synthetic adsorbents. Further, the article describes the possible application of adsorption-based water remediation technology for wastewater-fed aquaculture.

Municipal wastewater is a valuable resource because of its immense nutrient and water reuse potentials though untreated sewage has negative impacts on environment and human health. Properly treated wastewater is, however, safe and can be reused for aquaculture, agricultural and landscape irrigation, industrial processes, etc. In urban areas, reclaimed wastewater are used mainly for non-potable purposes such as recreation centre; sports grounds; school yards; play grounds; edges and central reservations of highways; irrigation of landscaped areas around public, residential, commercial and industrial buildings; and many other allied sites. Partially reclaimed wastewater is used for decorative and ornamental purposes such as fountains, reflecting pools and waterfalls, etc. It is frequently used for fire protection and toilet and urinal flushing in commercial and industrial buildings. In general, low-quality wastewater is widely used for agriculture and aquaculture; high-income countries, however, use treated wastewater for agriculture and landscape irrigation and for different food crops and other crops and nursery products. Currently, industrial water consumption was up to 22% of global water use. Industrial water use in Europe and North America accounted for half of their total water use, whereas in developing countries, it was about 4–12% of national water use, though there is enough scope for increase. Wastewater can be reused within a business itself or between several businesses through industrial symbiosis. The exchange of waste products for the mutual benefits of two or more businesses is also known as industrial symbiosis. It is suggested that the high cost-treated wastewater should be made efficient in use, and there should be appropriate sector-wise use of recycled wastewater. Efficiency of recycling of wastewater implies that allocation of recycled water to different sectors be made in such an optimal way that the overall economic efficiency is maximized. Recycled water is often more expensive than existing water supply. Efficiency of wastewater recycling in developed countries should be increased to reduce the cost of supply of recycled water so that it can compete efficiently with alternative sources of water. In cost-effective analysis, costs included both direct and indirect costs that are associated with the programme together with the intangible positive and negative externalities. An effective planning, management and regulations are necessary for profitable reuse of municipal wastewater for different economic-driven activities.

In view of present scarcity and qualitative degradation of freshwater due to myriad factors such as rapid rise in population growth, indiscriminate use of insecticides and pesticides, industrialization, global warming, and many others, wastewater has been considered as potential resource with its multiple types of reuse and applications in industry, urban areas, agriculture, irrigation, aquaculture, etc. The economic as well as environmental benefits of wastewater are immense by the way of reducing pollution and generating income and employment and conserving water resource. In the process of reusing wastewater in aquaculture, the system incurs some costs which are regarded as externality costs in addition to capital cost and operational costs of farms. This externality costs are social costs incurred for public health protection as the system is associated with health risk. This chapter attempts to examine all the positive as well as negative impacts of wastewater aquaculture and quantify the impacts. In cost-benefit analysis, total benefits accrued are weighed against total costs incurred. The conventional cost-benefit analysis of wastewater aquaculture is not sufficient to evaluate the impact as it does not take into account the indirect benefits (costs) of environmental impacts which are nonmonetary issues being public good in nature. In order to perform a comprehensive cost-benefit analysis, this study attempts to evaluate all these environmental, social, and ecological impacts by valuing them in monetized way by eliciting people’s willingness to pay (WTP), shadow price, and opportunity cost. Appropriate policy measures are suggested for maintenance, proper management, monitoring, safeguarding public health, and upscaling of the system with the objective to maximize economic, environmental, and social gain with minimum costs and sustainable development.

Wetlands are renewable and cost-effective complex nature of integrated natural biological resources. The wise use of aquaculture in the form of sewage-fed fishery provides a multitude of ecological functions such as flood reduction, groundwater recharge, habitat and biodiversity restoration, employable opportunity, etc. Wetlands are classified into 19 categories to include all varied nature of wetlands starting from plain land to high altitude as well as man-made to natural. Sharp decline or destruction of these ecosystems due to serious human intervention poses a threat to environmental sustainability. The present study highlights the steps of impact assessment, its different processes, evidences of impact assessment, impact analysis using diverse parameters to establish a report on management and monitoring of wetlands with special reference to East Kolkata Wetlands (EKW). The US Environmental Protection Agency (USEPA) has adopted three tiers or levels of methods for assessment system. East Kolkata Wetlands are unique ecological sensitive areas and are established as wise use of wetlands where the city sewage is used by mastering the activities of resource recovery. It also focused on the process of initial environmental examination (IEE) and strategic environmental assessment (SEA) which are recognized as the outcome of Agenda 21. Finally, impact analysis of biological organisms, especially fish through histological, histochemical, topological, enzymological and hormonal studies would be the important and added methods and techniques for future workers in the process of conceptual modelling on wetlands.

The United Nations Conference on the Human Environment, 1972, declared environment of quality is the basic right of human being. It laid emphasis on protection and improvement of environment for inter- and intra-generational equity. India as a participatory nation by the 42nd amendment of the constitution incorporated provisions under Art. 48A and Art. 51A (g) for protection and improvement of natural environment. Environment (Protection) Act, 1986, is the elaborate text of such constitutional mandate. The Act has made provisions for creation of institutions to shape an environmentally sound future. Consequently, by considering alarming effects of wastes − solid, liquid or e-waste – on environment, various rules are framed by the Central Government for the establishment of regulatory authorities to manage the situation. Present study covers the enforceability of such laws and rules to achieve the end, i.e. salubrious environment for all.