This paper examines the environmental impact of the use of compacted sewage sludge:red gypsum (SS:RG) mixture as intermediate landfill cover in terms of yield and quality of leachate as characterised by hydraulic conductivity and leaching behaviour. A series of column tests using the constant head method is carried out by percolating the synthetic leachate through samples that have been compacted at various degrees (60, 70, 75, 80 and 85%). The leachate quality is monitored at pre-determined days for pH, COD, Cu, Fe and Zn. In general, hydraulic conductivity decreases in three stages, in which the first stage is mainly attributed to the particle rearrangement and hydration of calcium silicate hydrate (CSH). The hydration of CSH increases the pH, which causes the heavy metal to precipitate and be entrapped within the matrices of CSH gel, thereby further reducing the porosity and hydraulic conductivity. A minimum of 75% compaction has shown favourable final porosity, hydraulic conductivity, and leachate quality, although a minimum of 80% compaction is recommended in order to achieve a satisfactory compressive strength of greater than 345 kPa for a landfill operation.

This study aims to determine suitable biochar precursor for local production of biochar as an alternative low-cost solution to address the persistent water supply issue in rural areas in Sarawak. A series of physicochemical characterization and adsorption studies were conducted for biochar pyrolysed from bamboo, dried leaves, wood shavings, rice husk, tree branch and wood chip, in a stainless-steel canister (without oxygen) at 600oC for three hours using a muffle furnace. Bamboo was the only precursor which fulfilled the requirements for water treatment in rural areas, i.e., biochar yield, structural integrity in water and adsorption characteristics. The pyrolysis of bamboo achieved a biochar yield of 32.8%, which attributed to the high fixed carbon content of 70.9% required for adsorption. The biochar consisted of homogeneous carbon structures with BET surface area of 317 m2/g, total pore volume of 0.189 cm3/g and micropores averaging 1.218 nm, which demonstrated favourable adsorption characteristics. The selection of bamboo as precursor is practical in rural areas as it is easily obtained and safe to be pyrolyzed into biochar. The application of biochar for water treatment helps to overcome the water supply issues and promote sustainable biomass waste management in rural areas.

Manganese slag is a by-product from the production of ferrosilicon and manganese alloys. It has been found to possess pozzolanic properties and is therefore suitable for use in concrete mixtures. This paper investigates the properties of normal concrete with ground manganese slag as a binder replacement in terms of workability, compressive strength, flexural strength, and leaching characteristics. In this study, it is found that using ground manganese slag as a binder replacement increases the slump of fresh concrete. It is also found that using ground manganese slag as a binder replacement reduces both the development of compressive and flexural strengths. However, at a 10% binder replacement rate, the deterioration is considered minimal. The results of leaching characteristics from 'The Tank Test' show that using ground manganese slag as a binder replacement increases the alkalinity of the solution surrounding the concrete, indicating that the metal ions in the ground manganese have diffused and dissolved in the solution.