Sudha Goel

Solid waste management in Kolkata, India: practices and challenges.

This paper presents an overview of current solid waste management (SWM) practices in Kolkata, India and suggests solutions to some of the major problems. More than 2920ton/d of solid waste are generated in the Kolkata Municipal Corporation (KMC) area and the budget allocation for 2007-2008 was Rs. 1590 million (US

Factors influencing arsenic and nitrate removal from drinking water in a continuous flow electrocoagulation (EC) process

40 million), which amounts to Rs. 265/cap-y (US

Removal of Natural Organic Matter (NOM) from Drinking Water Supplies by Ozone-Biofiltration

6.7/cap-d) on SWM. This expenditure is insufficient to provide adequate SWM services. Major deficiencies were found in all elements of SWM. Despite 70% of the SWM budget being allocated for collection, collection efficiency is around 60-70% for the registered residents and less than 20% for unregistered residents (slum dwellers). The collection process is deficient in terms of manpower and vehicle availability. Bin capacity provided is adequate but locations were found to be inappropriate, thus contributing to the inefficiency of the system. At this time, no treatment is provided to the waste and waste is dumped on open land at Dhapa after collection. Lack of suitable facilities (equipment and infrastructure) and underestimates of waste generation rates, inadequate management and technical skills, improper bin collection, and route planning are responsible for poor collection and transportation of municipal solid wastes.

Willingness-to-pay for solid waste management service attributes: Kolkata Municipal Corporation area, India, as a case study

An experimental study was conducted under continuous flow conditions to evaluate some of the factors influencing contaminant removal by electrocoagulation (EC). A bench-scale simulation of drinking water treatment was done by adding a filtration column after a rectangular EC reactor. Contaminant removal efficiency was determined for voltages ranging from 10 to 25 V and a comparative study was done with distilled water and tap water for two contaminants: nitrate and arsenic(V). Maximum removal efficiency was 84% for nitrate at 25 V and 75% for arsenic(V) at 20 V. No significant difference in contaminant removal was observed in tap water versus distilled water. Increase in initial As(V) concentration from 1 ppm to 2 ppm resulted in a 10% increase in removal efficiency. Turbidity in the EC reactor effluent was 52 NTU and had to be filtered to achieve acceptable levels of final turbidity (5 NTU) at steady-state. The flow regime in the continuous flow reactor was also evaluated in a tracer study to determine whether it is a plug flow reactor (PFR) or constantly stirred tank reactor (CSTR) and the results show that this reactor was close to an ideal CSTR, i.e., it was fairly well-mixed.

Defluoridation of Groundwater Using Electrocoagulation and Filtration: Efficiency and Energy Consumption

Removal of natural organic matter (NOM) in biofilters can be affected by many factors including NOM characteristics, use of pre-ozonation, water temperature, and biofilter backwashing. Laboratory experiments were performed and a biofilter simulation model was developed for the purpose of evaluating the effects of each of these factors on NOM removal in biofilters. Four sources of NOM were used in this study to represent a broad spectrum of NOM types that may be encountered in water treatment. In batch experiments with raw NOM, the removal of organic carbon by biodegradation was inversely proportional to the UV absorbance (254 nm)-to-TOC ratio and directly proportional to the percentage of low molecular weight material (as determined by ultrafiltration). The extent and rate of total organic carbon (TOC) removal typically increased as ozone dose increased, but the effects were highly dependent on NOM characteristics. NOM with a higher percentage of high molecular weight material experienced the greatest enhancement in biodegradability by ozonation. The performance of laboratory-scale continuous-flow biofilters was not significantly affected by periodic backwashing, because backwashing was unable to remove large amounts of biomass from the filter media. Model simulations confirmed our experimental results and the model was used to further evaluate the effects of temperature and backwashing on biofilter performance.

Extent and rate of biodegradation of different organic components in municipal solid waste

This paper examines public perceptions towards qualitative and quantitative attributes of a solid waste management (SWM) system in terms of willingness-to-pay (WTP) values. A stated choice (SC) survey instrument was designed and data was collected from residents in the Kolkata Municipal Corporation (KMC) of West Bengal, India. Respondents were approached randomly and face-to-face interviews were carried out. The behavioural data collected from residents are analysed by developing a standard multinomial logit (MNL) model and model coefficients are used for calculating the WTP values. Using the WTP values, the total disutility of SWM system is expressed in the form of generalised cost (GC).

Degradation of Plastics

AbstractFluoride is a geogenic pollutant found in groundwater in several parts of the world. A possible treatment strategy for removing fluoride from groundwater to meet drinking water standards is the use of electrocoagulation (EC). EC has to be combined with filtration to meet drinking water standards for fluoride and turbidity. The objective of this study was to evaluate the use of iron (Fe) electrodes (mild steel) for defluoridation of groundwater using EC and filtration in continuous-flow mode. Different operating conditions were examined and included the use of baffles, varying flow rates, voltages, and different reactor configurations. The use of baffles was observed to increase removal efficiency. EC and filtration in continuous flow mode with Fe electrodes and no baffles gave a maximum removal efficiency of 36.2%. Addition of baffles improved efficiency to 42% with two baffles and 46.7% with one baffle; the difference between one versus two baffles was within analytical variability. The pH increa...

Development and Application of a Multi-Criteria Decision Making (MCDM) Tool for Solid Waste Management: Kolkata as a Case Study

Rates and extent of biodegradability of four different organic components of municipal solid waste (leaf litter, newspaper, magazine paper and A4 sheet) were evaluated under optimum conditions. Total solids (TS) removals in biotic samples ranged from 74.7% to 78.8% while volatile solids removals ranged from 75.7% to 84.8%. Significant biodegradation of tannin-lignin was observed for all four components and removals ranged from 53% to 79.5%. Biodegradation rates were measured for all components and were found to fit second-order kinetics best. Biodegradation rate constants for all biotic samples ranged from 0.0317 to 0.0352 L/g-d. Control samples that had been autoclaved initially had higher biodegradation rates ranging from 0.0303 to 0.0537 L/g-d.

Forecasting Solid Waste Generation Rates

Today, plastics are an integral part of modern society. Living without plastics is almost impossible ever since their mass production began in the 1950s (Barnes et al. 2009). Plastics are versatile materials mainly due to their molecular structure and additives, and have many different positive applications that have eased human life to a great extent. However, plastics are a major treatment and disposal problem in urban solid waste management as plastics are relatively inert and non-biodegradable (Nayak et al. 2011). It is an undeniable fact that the environment and its biodiversity is greatly disturbed and damaged as a result of the rampant and uncontrolled use and disposal of these non-biodegradable materials (Barnes et al. 2009; Teuten et al. 2009). The impact of plastics on the environment is now a global concern since treatment and disposal methods are limited while rates of production and usage are increasing. Incineration of these plastic wastes generates toxic and harmful gases causing air pollution and is a common practice in many less developed and developing countries as appropriately engineered/planned landfill sites to dispose these wastes are very limited. Additionally, many disposal methods that are not acceptable like open dumping, uncontrolled incineration, unscientific composting and improper landfilling are often followed in countries like India (Kandakatla et al. 2012). Increasing concern among people about this problem has stimulated interest in the field of biodegradation of polymers such as polyethylene and polystyrene, etc., which are very stable in nature, and are not readily biodegradable. Globally, about 140 million tonnes of synthetic polymers are produced every year (Masayuki 2001) and only about 10% of these materials are recycled or reused as the disposal options are extremely limited.

Recovery of Manganese from Scrap Batteries of Mobile Phones

Solid Waste Management (SWM) is a major challenge for developing countries due to rapid increase in Solid Waste (SW) generation rates and financial constraints for proper management. Poorly managed SW causes severe consequences to society like financial and aesthetic degradation, environmental pollution and is a serious health hazard. SWM consists of six functional elements: generation, storage, collection, transfer, processing or treatment and disposal. Current regulations hold the administrative, i.e., municipal authority responsible for SWM and all expenditure on collection, transfer, processing and disposal of SW has to be met using the financial resources available. The main sources of revenue for any municipal authority are municipal or property tax and octroi. In a survey of municipal budgets and revenues for five major cities in India, 38 to 83% of the revenues were derived from these sources (Sekhar and Bidarkar 2013). Non-tax revenue, grants and other contributions formed the remaining part of the total revenues. In general, policy makers prepare SWM plans by optimizing expenditure on collection, transfer, processing and disposal of SW which is proportionate to municipal tax based on direct costs to households. Additional expenditure to be incurred by the municipal authority in improving the system has to be recovered from the community as additional municipal tax. Also, any savings by the municipal authority are transferred to the households in terms of tax relief. However, these SWM plans fail to account for inconvenience costs to users and environmental costs.