Assessment of municipal solid waste from households in Khulna city of Bangladesh.

Waste management is a major concern for both developed and developing countries, with a particular focus on household waste because it makes up a significant proportion of municipal waste. The aim of this study is to assess the state of solid waste management practice in Khulna, as well as to characterize and quantify municipal solid waste as a step toward effective management. To collect information on the existing waste management methods, structured questionnaires were used to conduct surveys of household residents. In this study, whole wards (31 wards) of Khulna City Corporation (KCC) were clustered in 9 groups and selected one ward from each group. To analyze household waste, 75 households from each ward were selected and collected waste for 7 days. The selected household was categorized into five different socioeconomic strata such as low-income, lower-middle-income, middle-income, higher-middle-income and higher-income families. Besides, the assessment was carried out on the production and characterization of household waste that was produced in KCC. The waste samples were quantified, separated and characterized in the laboratory. Results reveal that biodegradable waste is the most prominent type and its percentage is about 81 %. The amount of waste production is positively correlated with income level. The waste generation rate of households for high-income families was 0.652 kg/cap/day while this rate got almost half for a low-income family and its value is o.312 kg/cap/day. Source separation of waste plays a vital role to reduce plastic leakage to the SDP. The result shows the proportion of plastic in mixed waste and source-separated waste after sorting by the waste collector was 4.04 % and 2.99 %, respectively. Survey results show that 42.96 % of respondents think that the source-separated waste should be collected during the period of 12pm to 02pm. A proposed management process was developed for household waste based on the output of this study.

Effects of using arsenic-iron sludge wastes in brick making.

The arsenic-iron sludge generated in most of the treatment systems around the world is discharged into the nearest watercourse, which leads to accumulative rise of arsenic and iron concentrations in water. In this study, attempts were made to use the arsenic-iron sludge in making bricks and to analyze the corresponding effects on brick properties. The water treatment plant sludge is extremely close to brick clay in chemical composition. So, the sludge could be a potential substitute for brick clay. This study involved the addition of sludge with ratios 3%, 6%, 9% and 12% of the total weight of sludge-clay mixture. The physical and chemical properties of the produced bricks were then determined and evaluated and compared to control brick made entirely from clay. Results of different tests indicated that the sludge proportion and firing temperature were the two key factors in determining the quality of bricks. The compressive strength of 3%, 6%, 9% and 12% sludge containing brick samples were found to be 14.1 MPa, 15.1 MPa, 9.4 MPa and 7.1 MPa, respectively. These results indicate that the compressive strength of prepared bricks initially increased and then decreased with the increase of sludge proportion. Leaching characteristics of burnt bricks were determined with the variation of pH at a constant temperature. The optimum amount of sludge that could be mixed with clay to produce good bonding of clay-sludge bricks was found to be 6% (safely maximum) by weight.

Association of Vibrio cholerae O1 with the cyanobacterium, Anabaena sp., elucidated by polymerase chain reaction and transmission electron microscopy.

It has been hypothesized that Vibrio cholerae is an autochthonous flora of the estuarine and brackish water environment. Zooplankton and phytoplankton have been considered as possible reservoirs. The present study was carried out in microcosms to confirm the role of a cyanobacterium, Anabaena sp., as a reservoir of V. cholerae O1 using culture, polymerase chain reaction (PCR) and immunoelectron microscopy. Survival of culturable V. cholerae in microcosms was monitored by using tellurite taurocholate gelatin agar. Culturable V. cholerae were detected for up to 1 h in association with Anabaena sp. from a microcosm. However, viable but nonculturable (VBNC) V. cholerae O1 were detected for up to 25 months using PCR and immunoelectron microscopy. Results also showed that VBNC V. cholerae can multiply and maintain their progeny in the mucilaginous sheath of Anabaena sp. This is the first time that PCR and immunoelectron microscopy have been used to detect nonculturable V. cholerae in association with Anabaena sp. This study further clarifies the role of Anabaena sp. as a possible reservoir of cholera.