M. H. Rahman

Application of low-pressure nanofiltration coupled with a bicycle pump for the treatment of arsenic-contaminated groundwater☆

Abstract A nanofiltration (NF) membrane process coupled with a bicycle pumping system was examined by using arsenic-contaminated tube well water in a rural area of Bangladesh. It was operated under the conditions of low recovery and low operational pressure. It was proposed using both permeate and concentrate of NF membranes for drinking water and another purpose. Rejection characteristics of arsenic compounds such as arsenite [As(III)] and arsenate [As(V)] were also investigated. Arsenite, a neutral solute at pH 8, showed lower rejection than arsenate, which existed in ionized forms at pH 8. In this sense the pre-oxidation of arsenite to arsenate was necessary to obtain safer drinking water using the NF process. Furthermore, the reverse osmosis (RO) process could be operated under the conditions of high operational pressure at 4MPa by using a bicycle pedal pump. Rejection of arsenite and arsenate with the RO membrane was over 95%. However, treatment of concentrate with a high concentration of arsenic might be necessary for the application of the RO process where recovery was obtained at 66%. A high recovery of 66% was delivered at three times a higher concentration of arsenic in concentrate than feed water. Consequently, a low-pressure NF process with the pre-oxidation of arsenite to arsenate or the RO process coupled with a bicycle pumping system could be applied to the treatment of arsenic-contaminated groundwater in areas where electricity supply is not efficient or feasible

Unplanned urbanization: Assessment through calculation of environmental degradation index

Urbanization is an inevitable phenomena for the country like Bangladesh. The push and pull factors help to migrate people from rural area to urban area. As a result haphazard and unplanned urbanization create environmental degradation. Survey data reveals that inadequate solid waste disposal services, lack of adequate public water supply, traffic congestion, water logging, air pollution, noise pollution, hill cutting are the main problems in the city area. Concentration of dust as well as SOx, NOx exceeded the allowable limit at the selected points. Groundwater level of Sylhet city has a considerable lowering over the last few decades. It has lowered from 3380 mm below ground in 1982 to 7880 mm below ground. Sylhet is located in highly seismic risk zone but most of the buildings and other structures in this area are constructed without considering earthquake risk. Environmental degradation index was calculated based on economical condition of the country.

Composting barrel for sustainable organic waste management in Bangladesh

To ensure quick and uniform aerobic stabilization of biowaste through domestic composting and to prevent malodorous emissions, two modifications were made to a conventional steel barrel composter by: (1) providing 0.0125 m diameter openings throughout the sides and (2) placing a 0.0254 m diameter perforated polyvinyl chloride (PVC) pipe in the middle portion of the barrel. The volume of composting waste before modification of the composting barrel was 40% of the original volume and it was 70%, 4 weeks following the modifications. In addition, the nutrients in the compost were found to be in a more suitable range after modification of the composting barrel. The carbon–nitrogen ratio (C/N) of the compost was in the ideal range of 11–15 in the modified composting reactor but it was quite high (24–25) in the conventional barrel. This modified barrel composting plant proved to be an efficient, eco-friendly, cost-effective solution for the management of organic solid waste materials in developing and technologically less sophisticated countries such as Bangladesh.

Climate Change Impacts and Adaptation Strategies for Bangladesh

Climate Change and Growth in Asia is a comprehensive analysis of the major issues of climate change and global warming and their possible impacts on the growth of major Asian economies. The book addresses the climate change crisis in Asia within the context of three major challenges to growth: population, poverty and greenhouse gas emissions.