Electroless plating wastewater contains mixed metals element. Although precipitation is the most common method applied to remove metals from the wastewater, it fails to completely precipitate all the metals at a single pH. The present work evaluates the effectiveness of the sulphide and the hydroxide precipitation for removal of nickel, zinc and copper from industrial wastewater, namely acid rinse and nickel rinse samples. The optimum pH and coagulant dosage were determined via Jar Test for both types of samples. Sulphide precipitation removed heavy metals more efficient than hydroxide precipitation. For the acid rinse sample, 95.32% of nickel was removed using sulphide precipitation while 76.66% removal using hydroxide precipitation. For nickel rinse sample, 93.75% of zinc was removed using sulphide while 68.8% removal using hydroxide. 65.75% of nickel was removed using both sulphide and hydroxide. Total removal of copper was achieved for both hydroxide and sulphide precipitation, either from acid rinse or nickel rinse samples.

Municipal solid waste is a growing concern in cities of developing countries and households are the main contributor. Lack of reliable data sources remain one of the major drawbacks for deciding on effective waste management option. However, continued growth in municipal waste if left unattended will only intensify the problem and thus demands proactive action. Therefore, the objective of this study is to analyse waste composition and to evaluate the possible planning for effective management. The study area puncak alam selected because it is one of the rapid development area in Kuala Selangor. Using a stratified sampling method, 200 households selected from residential area. The rate of household waste generation in puncak alam is found to be 1.0 kg/capita/day and estimated each household generate 2.5kg/day. Household waste composition was 60 % organic waste, 24% recyclable waste that comprised of 8% paper and paper products,3% glass, 4% metal, 9% plastic, and 11% other waste. Organic waste has the highest score and if not managed properly, creates serious health and environmental hazards. It could be managed efficiently by composting at household and local government level.

Plating industry wastewater is one of the processes that may contain various types of heavy metals. The most common heavy metals that mostly found are copper, nickel, cadmium, chromium, silver, zinc, and lead. In this study, three types of metals which are copper, zinc and chromium trivalent were removed using hydroxide precipitation and sulphide precipitation. Both performances of the method were observed and compared. A jar test was used to determine the optimum pH, coagulant dosage and precipitant dosage. The coagulant and precipitant used in this experiment was ferric chloride (FeCl3), poly aluminium chloride (PAC), sodium hydroxide (hydroxide precipitant) and sodium sulphide (sulphide precipitation) respectively. In order to remove chromium trivalent, sodium metabisulfite was used to reduce chromium hexavalent to chromium trivalent. Based on the result, hydroxide precipitation can remove 86.61% of copper, 99.81% of zinc and 99.99% of chromium trivalent. While, for sulphide precipitation, 93.91% of copper, 99.37% of zinc and 99.99% of chromium trivalent were removed. Therefore, sulphide precipitation can remove better mixed heavy metals, thus it also produces less total suspended solid compared to hydroxide precipitation.

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The aim of this study is to investigate odour emission profiles from storage of local food waste and to assess the potential health risk caused by exposure to volatile compounds. Food waste decomposition process was conducted for 14 days and kept at 20°C and 30°C in self-made bioreactor. VOCs emissions from both samples were collected at different stages of decomposition starting at day 0, day 1, day 3, day 5, day 7, day 10, day 12 and day 14. It was analyzed using TD-GC/MS. Findings showed that various VOCs were released during decomposition of food waste. Compounds produced were influenced by time, temperature and the physico-chemical characteristics of the compounds. The most abundant compound released was dimethyl disulfide. Potential health risk of exposure to this compound is represented by hazard ratio, HR, calculated at 1.6 x 1011. Since HR equal to or less than 1.0 is considered negligible risk, this indicates that the compound posed a potential risk to human health.