Developmental Design of Anaerobic Wetland System for Mining Waste Water Treatment

Abstract

Problem statement: Tin mining is one of the oldest industries in Malaysia that have started since 1820s. These mining activities have resulted in about 13,700 hectors of tin tailings throughout the peninsula. These tailings have created numerous environmental problems such as threat to natural reserves due to landscape changes, damage to natural drainage, pollution and destruction of natural habitats. Approach: This research provided an approach for designing a constructed wetland system for treatment of tin-contaminated wastewater from mining catchment, a system that is known to provide a more economical treatment than the conventional system. Design of wetland was mostly based on the review of scientific literature, theoretical modelling and verification of performance via a pilot system. Results: Initially, physio-chemical characteristics and concentration of heavy metals in the soil and ponds were evaluated. It was found that the soil and water quality of area is highly degraded. This study will help for the design of the wetland for wastewater treatment. The study area consists of five mined out ponds in the catchment, each pond arranged in series with a 48 h hydraulic retention time. Wetland system comprises of three compartments in series-an ‘inflow’ pond receiving untreated tailings water overflowing into a wetland compartment, which in turn overflows into an ‘outflow’ pond receiving the now treated water. Each compartment filled with approximately 50 cm depth of a mixture of the cattle manure as (25%) and municipal waste compost (75%) as substrate. Waterproof baffles in each wetland compartment serve to increase the flow path of the water, thereby increasing the potential for sulphate retention. Additionally 30 tonnes of limestone will be deposited at the far end of the wetland, to facilitate final pH adjustment if it should be required. On site a computer connected to the pumps regulates the flow of tailings water through the systems. Conclusion: The planting density chosen is based on similar research on constructed wetlands. Proposed anaerobic wetland is first of its kind introduce for mining waste water treatment in Malaysia. Good results have achieved on laboratory scale operations for this system.