B. Sen Gupta

Adsorption characteristics of Cu and Ni on Irish peat moss

Peat has been widely used as a low cost adsorbent to remove a variety of materials including organic compounds and heavy metals from water. Various functional groups in lignin allow such compounds to bind on active sites of peat. The adsorption of Cu(2+) and Ni(2+) from aqueous solutions on Irish peat moss was studied both as a pure ion and from their binary mixtures under both equilibrium and dynamic conditions in the concentration range of 5-100mg/L. The pH of the solutions containing either Cu(2+) or Ni(2+) was varied over a range of 2-8. The adsorption of Cu(2+) and Ni(+2) on peat was found to be pH dependent. The adsorption data could be fitted to a two-site Langmuir adsorption isotherm and the maximum adsorption capacity of peat was determined to be 17.6 mg/g for Cu(2+) and 14.5mg/g for Ni(2+) at 298 K when the initial concentration for both Cu(2+) and Ni(2+) was 100mg/L, and the pH of the solution was 4.0 and 4.5, respectively. Column studies were conducted to generate breakthrough data for both pure component and binary mixtures of copper and nickel. Desorption experiments showed that 2mM EDTA solution could be used to remove all of the adsorbed copper and nickel from the bed.

Microfiltration of water-based paint effluents

Abstract The major hurdle associated with water recycling in water-based paint manufacturing processes is microbial contamination and related deterioration of product quality and shelf life. The common problems associated with microbial degradation are change in viscosity, pH, colour and loss of surface adhesion properties. Owing to these reasons, water recycling is not widely practised in water-based paint manufacturing processes. The present study focuses on tertiary treatment of effluent by chemical coagulation and cross-flow microfiltration (0.2 μm pore size) to produce water of sufficient quality for reuse in various stages of water-based paint manufacturing. The coagulation and flocculation were carried out in a ‘jar test’ rig at a controlled pH, and coagulant dosage was optimised by turbidity and zeta potential measurements. The filtrate was subjected to cross-flow microfiltration and permeate was tested for necessary quality attributes. Screening of aerobic microbes and fungi were conducted by streaking the samples on nutrient agar and malt extract agar, respectively. Iron sulfide agar tubes were used for screening anaerobic microbes or the sulfate reducing bacteria. The tests showed that permeate was free from microorganisms. The process was implemented in a paint manufacturing plant in Malaysia, which resulted in 55% reduction in water consumption.

A simple chemical free arsenic removal method for community water supply - A case study from West Bengal, India

This report describes a simple chemical free method that was successfully used by a team of European and Indian scientists (www.qub.ac.uk/tipot) to remove arsenic (As) from groundwater in a village in West Bengal, India. Six such plants are now in operation and are being used to supply water to the local population (www.insituarsenic.org). The study was conducted in Kasimpore, a village in North 24 Parganas District, approximately 25 km from Kolkata. In all cases, total As in treated water was less than the WHO guideline value of 10 microg L(-1). The plant produces no sludge and the operation cost is 1.0 US

Arsenic in groundwater and its influence on exposure risks through traditionally cooked rice in Prey Vêng Province, Cambodia

per day for producing 2000 L of potable water.

A survey of tap water quality in Kuala Lumpur

Arsenic (As) contamination of communal tubewells in Prey Vêng, Cambodia, has been observed since 2000. Many of these wells exceed the WHO As in drinking water standard of 10 μg/L by a factor of 100. The aim of this study was to assess how cooking water source impacts dietary As intake in a rural community in Prey Vêng. This aim was fulfilled by (1) using geostatistical analysis techniques to examine the extent of As contaminated groundwater in Prey Vêng and identify a suitable study site, (2) conducting an on-site study in two villages to measure As content in cooked rice prepared with water collected from tubewells and locally harvested rainwater, and (3) determining the dietary intake of As from consuming this rice. Geostatistical analysis indicated that high risk tubewells (>50 μg As/L) are concentrated along the Mekong Rivers east bank. Participants using high risk tubewells are consuming up to 24 times more inorganic As daily than recommended by the previous FAO/WHO provisional tolerable daily intake value (2.1 μg/kg BW/day). However, As content in rice cooked in rainwater was significantly reduced, therefore, it is considered to be a safer and more sustainable option for this region.

Stability and performance enhancements of Electrokinetic-Fenton soil remediation

A safe drinking water programme known as The National Drinking Water Quality Surveillance Programme (NDWQSP) was launched by the Ministry of Health, Government of Malaysia in 1983 to ensure safe practices in water treatment and distribution. The aim of this work was to assess the effectiveness of this programme in the improvement of tap water quality in and around Kuala Lumpur. The results indicate that there was no microbial contamination in 100 random samples collected from 20 selected areas. Other quality parameters such as colour, pH, turbidity, hardness, magnesium, sulphate and chloride were within acceptable limits. Heavy metals such as Cu2+, Pb2+, Cr (total), Ni2+, Cd2+, Fe (total) and Mn (total) were also under control. The only exception was Ba2+, which did not comply with the standard and was up to ten times higher than the guideline value. Moreover, there was significant variation in water quality as indicated by the test results.

Clarification of yeast by colloidal gas aphrons

Electrokinetic process is a potential in situ soil remediation process which transports the contaminants via electromigration and electroosmosis. For organic compounds contaminated soil, Fenton’s reagent is utilized as a flushing agent in electrokinetic process (Electrokinetic-Fenton) so that removal of organic contaminants could be achieved by in situ oxidation/destruction. However, this process is not applied widely in industries as the stability issue for Fenton’s reagent is the main drawback. The aim of this mini review is to summarize the developments of Electrokinetic-Fenton process on enhancing the stability of Fenton’s reagent and process efficiency in past decades. Generally, the enhancements are conducted via four paths: (1) chemical stabilization to delay H2O2 decomposition, (2) increase of oxidant availability by monitoring injection method for Fenton’s reagent, (3) electrodes operation and iron catalysts and (4) operating conditions such as voltage gradient, electrolytes and H2O2 concentration. In addition, the types of soils and contaminants are also showing significant effect as the soil with low acid buffering capacity, adequate iron concentration, low organic matter content and low aromatic ring organic contaminants generally gives better efficiency.

A survey of sewer rehabilitation in Malaysia: application of trenchless technologies

Colloidal gas aphrons or CGAs were employed in a flotation column for the recovery of yeast from aqueous solutions. The CGAs sparging rate was a critical factor that governed the efficiency of the process. The separation efficiency was less than 30% at a sparging rate of 1.3 ml sec−1 and increased exponentially up to 90% as the sparging rate was increased to 2.4 ml sec−1. Whereas there was no appreciable change in the separation efficiency with CGAs sparging rates for high initial feed concentrations, the maximum achievable efficiency decreased with an increase in the initial feed concentration. In general, a decrease in pH will improve the separation efficiency.

Transient Crystal Size Distribution in DTB and FC Crystallizers

This work presents a review of applicable sewer rehabilitation options using trenchless technology in Malaysia. The typical problems faced in wastewater collection systems are analysed and factors that determine the selection method are outlined. This study also highlights the necessary steps to be taken prior to the rehabilitation work. The trenchless technology reviewed here comprises repair, renovation and replacement options. The cost-effectiveness of different rehabilitation methods was identified to assess the economic viability of various options in the Malaysian context. This study reveals that not all the trenchless technologies available in the market are suitable for use in Malaysia, mainly due to incompatibility of the rehabilitation materials used. Furthermore, as trenchless rehabilitation generally involves higher capital outlay than open-cut methods, the choice of rehabilitation method has to be made on a case-to-case basis.

Studies on fixed bed biosorption and elution of copper using polyvinyl alcohol-immobilized seaweed biomass

This work deals with the transient analysis of crystal size distribution (CSD) for imperfectly mixed draft tube baffled (DTB) and forced circulation (FC) crystallizers. The DTB and FC crystallizers are described by the Compartmental and Mixed models respectively. Monte Carlo (MC) scheme has been employed for simulation purposes. The simulation results have been compared with the available experimental data of BENNETT and VAN BUREN for continuous urea crystallizers.