Impact assessment of treated/untreated wastewater toxicants discharged by sewage treatment plants on health, agricultural, and environmental quality in the wastewater disposal area
Introduction
Soil and water quality are issues, which affect the quality of our food, health and environment in general. Growing levels of pollution and over-consumption of resources demand some sort of solution. Anthropogenic impact on natural environments and especially on aquatic ecosystems is currently a topic of increasing concern. Deterioration of surface water and especially river water quality has recently observed in many aquatories (Boehm et al., 2002; Campolo et al., 2002; Jain, 2002; Nobukawa and Sanukida, 2002; Tara et al., 2003). The potential causes of such a situation are various point and non-point sources (Duda, 1993). Most of these sources lead to the pollution of rivers. The quality of river water may vary depending on the geological morphology, vegetation and activities in the catchments, as well as on the location of the sampling site, either upstream in the mountains or the lower reaches of the river course (Markantonatos et al., 1995; Brezonic et al., 1999).
The Ganga is the most important river system in India. It rises in the Gangotri glacier in the Himalaya mountains at an elevation of 7138 m above mean sea level in the Uttar Kashi district in the state of Uttaranchal, India. Already half a billion people almost one-tenth of the world’s population live within the river basin at an average density of over 500 per square kilometer. This population is projected to increase to over one billion people by the year 2030. Today the 2510 km long river supports 29 class I cities, 23 class II cities and 48 towns, and thousands of villages. Nearly all the sewage from these populations goes directly into the river, totaling over 1.3 billion liters per day. Further 260 million liters of industrial waste, run off from the 6 million tons of fertilizers and 9000 tons of pesticides used in agriculture within the basin enters into the river. A large quantity of solid waste including thousands of animal carcasses and several hundred human corps also released into the river every day for spiritual rebirth.
In view of this, Ganga Action Plan (GAP) was formulated in the 25 class I towns along the bank of the river based on comprehensive survey of the Ganga basin. In the planning stages of GAP-I in the mid 80s, conventional technologies for sewage treatment were adopted with designs on normative basis by the state implementing agencies due to lack of experience in this area. For the first time in the country under integrated sanitation project of Indo-Dutch cooperation of the Ganga Action Plan, Phase-I, and innovative sewage treatment technology called up-flow anaerobic sludge blanket process (UASB) was experimented with sewage of 5 MLD capacity and had been in successful operation since then. Sewage treatment plants (STPs) provide agriculture benefits by supplying irrigation and non-conventional fertilizer. Farmers for irrigation in the adjoining villages use partly treated water from STPs with significant amount of nutrients. Therefore STPs under GAP, apart from reducing the pollution load of households and industrial effluents to meet pollution standard, provide irrigation and fertilizer benefits to farmers. There are about 35 STPs under GAP with 13 located in Uttar Pradesh, 7 in Bihar, and 15 in West Bengal. Besides providing irrigation, some of the STPs are supporting pisciculture, especially in West Bengal. All these STPs have capacity to treat a wastewater volume of 919.82 million liters per day. A variety of pollutants can be removed from the sewage by biological and chemical degradation, sorption to sludge or volatilization (Rogers, 1996). In different countries, studies have been carried out for the occurrence and removal of pollutants and comparative evaluation in sewage and landfill leachates (Hannah et al., 1986; Marttinen et al., 2003). Very few studies are available on the impact assessment of wastewater/sludge disposal on the environment quality. Thus the aim of this study was to investigate the impact assessment of treated/untreated wastewater toxicants discharged by sewage treatment plants on health, agriculture and environmental quality in the wastewater disposal areas.
Section snippets
Study area
To assess the impact of the wastewater/sludge disposal (metals and pesticides) on the environmental quality of the receiving/application areas around sewage treatment plants (STPs), two plants viz., UASB, Jajmau, Kanpur (5 MLD) and STP, Dinapur, Varanasi (80 MLD) were identified and selected for study. Environmental samples (surface water, ground water, soil, vegetables, crops, food grains, milk etc.) were collected from different villages, both in the receiving (exposed) viz., Shekhpur,
Chemicals and instrumentations
All the solvents and chemicals were of analytical grade. Distilled water was occasionally analyzed similar to wastewater samples to control the laboratory contamination if any. The pH measurements were made using a pH meter model Elico, L-27. An ANTEK-3000 Gas Chromatograph equipped with ECD/FPD and capillary column was employed for the analysis of BHC isomers, DDT isomers and metabolites, endosulfan, malathion, methyl parathion, ethion and dimethoate residue levels. The capillary column
Wastewater (untreated/treated)
The raw (untreated) and treated wastewater samples were collected from the inlet and outlet of both the sewage treatment plants (STPs) in Jajmau, Kanpur (5 MLD) and Dinapur, Varanasi (80 MLD) during the peak (morning and evening) and non-peak (noon) hours and analyzed for metals and pesticides. The metals and pesticides residue levels (mean) at the inlet and out let of the two-sewage treatment plants (Kanpur and Varanasi) are given in Table 1. The result of the physicochemical analysis and
Impact of wastewater toxicants (metals and pesticides)
The conventional type STPs are basically to reduce the organic load, these are not very effective in reducing the levels of metals and pesticides except that a large fraction of these toxicants present in the wastewater is retained with the sludge generated by STPs while the remaining part getting out with the treated wastewater/effluents.
Acknowledgements
The authors are thankful to the Director, Industrial Toxicology Research Centre, Lucknow for providing all necessary facilities for this work and consistent encouragement and guidance throughout the studies.
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