Management and treatment of landfill leachate by a system of constructed wetlands and ponds in Singapore.

Lorong Halus, Singapore's first landfill leachate treatment system, consists of a pre-treatment system (8,000 m(2)), five constructed reed beds (38,000 m(2)), five polishing ponds (13,000 m(2)), an education centre and a learning trail for visitors. Eight species of wetland plants (total 160,000 plants) were selected for their ability to uptake nutrients, tolerance to low phosphorus concentrations and resistance to pest infestations. The wetland was launched in March 2011 and water quality monitoring started in April 2011.

Effects of temperature on metal tolerance and the accumulation of Zn and Pb by metal-tolerant fungi isolated from urban runoff treatment wetlands.

Aims: To investigate the ability of two fungi to accumulate Zn and Pb, the effect of temperature on their metal tolerance and possible mechanisms involved in metal accumulation.

Methods And Results: Beauveria bassiana and Rhodotorula mucilaginosa isolated from constructed wetlands receiving urban runoff were grown in modified glycerol asparagine medium containing elevated levels of Zn and Pb at 30 degrees C. Beauveria bassiana accumulated up to 0.

Landfill leachate treatment by an experimental subsurface flow constructed wetland in tropical climate countries.

Municipal leachate was treated in an experimental unit of constructed wetlands of subsurface flow type. The parameters studied were organics (BOD and COD), solids and heavy metals (Zn, Ni, Cu, Cr and Pb). Using two types of emergent plants of Scirpus globulosus and Eriocaulon sexangulare, more than 80% removal was achieved for all the parameters.

The performances of vegetative treatment systems for highway runoff during dry and wet conditions.

The performances of two different highway runoff treatment systems, a horizontal subsurface flow-constructed wetland and a vegetated balancing pond, are described. Both systems have been assessed by collecting inlet and outlet grab samples during wet and dry weather conditions, and automatically controlled storm event samples have been obtained for the constructed wetland. Removal efficiencies are discussed for BOD (grab samples only), suspended solids, Cd, Cr, Cu, Ni, Pb, Zn, nitrate and sulphate, and explanations are offered for the trends observed under different weather conditions.

Treatment of agricultural wastewater in two experimental combined constructed wetland systems in a tropical climate.

Two designs of experimental combined constructed wetland systems were constructed: vegetated (Scirpus grossus Linn) subsurface horizontal flow bed followed by a vegetated vertical flow bed and a vegetated vertical flow bed over an unvegetated horizontal flow sand bed. The systems were used to compare the nitrification/denitrification efficiency in a tropical climate which has temperatures above an average of 25 degrees C throughout the year. The effluent from a biogas digester of pig farm wastewater with TKN and COD concentrations of approximately 400 and 1,000 mg/L was fed every 4 hours intermittently.

An experimental constructed wetland system for the treatment of highway runoff in the UK.

This paper compares the performance of an experimental highway runoff treatment system, incorporating a subsurface flow constructed wetland, with that of a vegetated balancing pond. Both systems are located on the same major road in the UK which opened in November 1998. Copper, chromium and nickel total aqueous metal concentrations, although low, have been consistently removed (maximum efficiencies of 67.

Nitrogen removal in a combined system: vertical vegetated bed over horizontal flow sand bed.

Pig farm wastewater creates various problems in many areas throughout Thailand. Constructed wetland systems are an appropriate, low cost treatment option for tropical countries such as Thailand. In this study, a combined system (a vertical flow bed planted with Cyperus flabelliformis over a horizontal flow sand bed without plants) was used to treat settled pig farm wastewater.

Artificial wetlands and water quality improvement.

This paper illustrates the role of plants to assist the treatment of water pollution in man-made wetlands in tropical and temperate climates. It also considers the potential for environmental education of these wetland systems. The management and natural treatment of pollution is described in the Mai Po Marshes, Hong Kong and a wetland in London which is also an important site for birds.

An assessment of the impact of motorway runoff on a pond, wetland and stream.

The impact of soil filtered runoff from a section of the M25 outer London motorway (constructed in 1981) on a pond, wetland and stream in a nature reserve was investigated by monitoring water, sediment. The tissues of the emergent plants Typha latifolia and Glyceria maxima collected from the pond were analysed for the heavy metals, Cd, Pb, Cu and Zn. Macroinvertebrates were monitored in the stream and biotic indices applied to the data.

The design of vegetative constructed wetlands for the treatment of highway runoff.

The Environment Agency for England and Wales are responsible for assessing the effects of highway runoff and for monitoring the treatment systems/procedures which have been introduced for the reduction of deleterious effects. The Agency is looking into the improvement of surface water management in terms of best management practices and plans to work in partnership with the Highways Agency to achieve this aim. Among the treatment options being considered are constructed wetlands.

The determination of the toxic influences to Gammarus pulex (amphipoda) caged in urban receiving waters.

: A statistical procedure comprising principal component analysis and multiple regression has been applied to the in situ mortality response data for Gammarus pulex caged downstream of a combined sewer overflow (CSO) and a surface water outfall (SWO). The mortality and heavy metal bioaccumulation responses of the species as well as seventeen different chemical and hydrological characteristics of the receiving watercourse were monitored continuously for 36 days. Flow rate, BOD5, suspended solids, total ammonia, total aqueous copper and lead concentrations and dissolved aqueous concentrations of zinc and copper influenced the mortality response of Gammarus pulex.