ICE - Institution of Civil Engineers - Virtual Library

An assessment is made of the performance of a horizontal flow sub-surface constructed wetland (SSCW) for polishing effluent from an activated sludge process (ASP) treatment plant. The results of experiments conducted at Mother Dairy Pilot Plant, New Delhi, India are reported in this study. The treated wastewater from the ASP was retreated by subsurface CW planted with Phragmites australius. CW has been extensively researched in Europe and USA. Very limited studies on the suitability of the CW have, however, been reported under tropical and subtropical climatic conditions. The parameters studied were pH, total suspended solids (TSS), total dissolved solids (TDS), chemical oxygen demand (COD), biochemical oxygen demand (BOD), PO₄-P, total Kjeldahl nitrogen (TKN), total coliforms (TC) and faecal coliforms (FC). The study was carried out for various temperatures, hydraulic and organic loading conditions. The average efficiency for TSS, BOD, TC and FC was found as 81·02, 88·93, 97·16 and 99·31% respectively under hydraulic loading varying from 24 to 74·8 l/m²/day. The highly encouraging results of these experiments have proved the viability of CW as tertiary (polishing) unit in tropical and subtropical climatic conditions.

Understanding of riverine and estuarine mixing processes remains limited, and predictions are highly sensitive to specific features of natural systems. One reason for this is the very complex variations of hydrodynamic and physio-chemical properties with the tidal phase. This study presents the results of two field works during which a range of flow and chemical parameters were recorded simultaneously at several locations along a small sub-tropical estuary. The studies were conducted in contrasting (wet and dry) conditions. Field measurements indicated that the hydrodynamics and water conductivity were dominated by tidal forcing and, to a lesser extent, by freshwater inputs. There were generally significantly greater differences between longitudinal sites than between vertical depths, although some marked differences were observed between the upper and lower estuarine zones. The comparative results between wet and dry field studies illustrated some marked stratification in wet weather along the whole of the estuary, implying that the surface samples were not representative of the average water column properties. Overall, the complexity of the hydrodynamics and water quality has some impact on water quality modelling of the system.

Densely populated Taiwan is situated in a highly seasonal subtropical region dominated by typhoon-generated hydrology. Flood and induced inundation occur frequently in the typhoon season and subsequently cause severe damage to property and loss of human life. There are significant challenges in effective disaster reduction and timely support for the authorities to mitigate floods and inundation. Recent advances in cyberinfrastructure in Taiwan have made it possible to build a synthetic system that is better suited to meet such challenges. This paper describes a human-centred system that has been deployed with a framework utilising cyberinfrastructure. It uses grid technology to integrate collaboratively inter-institutional resources and disciplines for flood mitigation. The human-centred system designed for this flood mitigation study comprises a real-time communication platform among geographically distributed institutions, a flood-monitoring sensor network system to assess current and historical flood situations and associated data collection, and computing and data grids to support flood forecast research. The method of linking information and data generated and delivered by the system to flood mitigation decision support is also explored. The flood mitigation grid has been fully utilised by the Taiwan Water Resources Agency.