Kitchen waste (KW) can be utilized to produce biogas due to its high biodegradability, calorific value and nutritive value to microbes, which will reduce our dependency on fossil fuels. The research work was conducted to investigate the production ability of biogas as an alternative energy from KW with co-digestion of cow manure (CM) through anaerobic digestion (AD). Firstly, three digesters were prepared to observe the individual degradation rate of KW, CM and co-digested KW with CM at room temperature (25°C~30° C) and at temperature of 37°C (mesophilic digestion) respectively and observed the degradation rate for co-digested KW with CM was higher than KW and CM alone. Secondly, three digesters were constructed to observe the effect of alkalinity at temperature 37° C and loading rate 200 gm/L. Three alkali (NaOH) doses 1.0%, 1.5% and 2.0% on wet matter basis of kitchen waste were applied to improve biodegradability and biogas production. The highest degradation rate was 6.8 ml/gm which was obtained from 1.5% NaOH and also observed that biogas production was almost doubled from treated KW than untreated KW. Finally, a portable biogas reactor was fabricated for pilot-scale biogas production which included an agitator and heating system. This reactor was operated at both 37° C and room temperature at a loading rate of 200 gm/L and observed that the digestion rate was faster at 37°C than room temperature. The prime object of this work was to investigate the prospect of kitchen waste for biogas production and ultimate protection of environment from the bad effect of methane gas that would be produced by uncontrolled anaerobic digestion.
The rapid growth of textile industry in Bangladesh plays an important role in economic development. The sludge from the wastewater treatment plant in textile units is considered hazardous as it is often contaminated with heavy metals of dyestuffs and chemicals. Currently, land filling is the most common practice for textile sludge disposal. Leaching of heavy metals from textile sludge is a growing concern in Bangladesh. This study attempts to find out an environment-friendly solution for the management of the textile sludge. In this study, sludge samples were collected from treatment plants of various textile units located at Savar, Gazipur and Narsingdi. An electric incinerator was designed, fabricated and installed for the incineration of textile sludge. The sludge samples were incinerated at 500 0 C, 700 0 C and finally at 800 0 C for different time intervals. The volume reduction of the sludge samples was nearly 80% at 800 0 C. The incineration techniques were used for volume reduction and destruction of the hazardous elements. The oven dried samples were powdered and mixed at various proportions (0%, 10%, 20%, and 30%) with clay for making the ceramic products and also mixed with sand, cement and aggregates for making blocks for the stabilization of heavy metals in sludge. The properties of ceramic products such as firing shrinkage, bulk density, leaching of Heavy metals and the compressive strengths were evaluated. Incinerated ash samples were also used for ceramic tiles and block preparations. The concentrations of heavy metal in leachate from the stabilized sludge samples were very low. The compressive strength, bulk density, water absorption of the stabilized sludge and ash samples were examined and the results showed that up to 10% of the raw sludge and 10-20% ash samples could be used for stabilization and/or solidification and additionally, 80% volume reduction of the raw sludge could be obtained.
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