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Abstract:Growing vegetables economically in the use of constructed wetland for wastewater treatment can play a role in overcoming water and food scarcity.Allium porrum L., Solanum melongena L., Ipomoea aquatica Forsk., and Capsicum annuum L. plants were selected to grow in hybrid constructed wetland (CW) under natural conditions. The impact of the ratio of nitrate to ammonium nitrogen on ammonium and nitrate nitrogen removal and on total nitrogen were studied in wastewater. Constructed wetland planted with Ipomoea aquatica Forsk. and Solanum melongena L. showed higher removal efficiency for ammonium nitrogen under higher ammonium concentration, whereas Allium porrum L.-planted CW showed higher nitrate nitrogen removal when NO 3 -N concentration was high in wastewater. Capsicum annuum L.-planted CW showed little efficiency for both nitrogen sources compared to other vegetables.

Constructed wetlands (CWs) are an aesthetic and sustainable form to treat wastewater, however, their performance can be increased by improving a number of factors. The pilot-scale hybrid constructed wetland (CW) system was the combination of constructed floating treatment wetlands (CFWs) and horizontal subsurface flow constructed wetlands (HSFCWs); operated for a year and covered all seasons. The research was conducted to investigate the performance of the CW system regarding water depth, spatial, and seasonal removal of pollutants. Nine economical plants species were selected and divided into four groups to grow in CW-I to CW-IV, respectively. Removal increased along the bed and most of the total phosphorus (TP) removal occurred in the second bed, whereas total nitrogen (TN) and ammonium (NH4) removal were associated with the plant root system and biomass. Optimum removal of nutrients with respect to water depth was at 35 cm. TN and NH4 removal patterns were similar in different CWs. TN and NH4 removal were higher during summer compared to winter; only CW-IV showed the opposite trend.

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Groundwater from 33 monitoring of peripheral wells of Karachi, Pakistan were evaluated in terms of pre- and post-monsoon seasons to find out the impact of storm water infiltration, as storm water infiltration by retention basin receives urban runoff water from the nearby areas. This may increase the risk of groundwater contamination for heavy metals, where the soil is sandy and water table is shallow. Concentration of dissolved oxygen is significantly low in groundwater beneath detention basin during pre-monsoon season, which effected the concentration of zinc and iron. The models of trace metals shown in basin groundwater reflect the land use served by the basins, while it differed from background concentration as storm water releases high concentration of certain trace metals such as copper and cadmium. Recharge by storm water infiltration decreases the concentration and detection frequency of iron, lead, and zinc in background groundwater; however, the study does not point a considerable risk for groundwater contamination due to storm water infiltration.

Abstract. The performance and the characteristics of a laboratory-scale ABR (anaerobic baffled reactor) were investigated during different seasons (summer, spring, autumn and winter). ABR successfully achieved COD removal efficiencies 74% during summer, 68% during autumn/spring and 62% during winter. Compartment I, II and III showed high removal rate of COD during whole study period. At lower OLR (organic loading rate), COD removal rate was high. The analysis of biogas production during all seasons showed downward trend with increase of HRTs (hydraulic retention time). Compartment I showed high VFA (volatile fatty acid) synthesis compared to others compartments. The ABR has the potential to provide a greater efficiency and be applicable for all type of seasons and temperature conditions.

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Limited water resources and ensuring access to clean water are critical environmental challenges, especially for the developing world. In particular, rural domestic wastewater has become a significant source for the pollution of freshwater bodies. A modified bio-ecological A2O-wetland system for rural wastewater treatment consisting of a biological unit (anaerobic baffled reactor, anoxic tank and oxic unit, A2O) and an ecological unit (horizontal flow constructed wetland) was developed, and key performance indicators were identified. The bio-ecological treatment system showed high removal efficiency for pollutants, successfully achieving 91%, 85%, 78%, and 92% removal efficiencies for chemical oxygen demand (COD), ammonium (NH 4 -N), total nitrogen (TN), and total phosphorus (TP), respectively. The concentrations of pollutants in the effluent from the system were lower than the Class 1 A regulated values of the Chinese National Standard GB18918-2002. The system offered high removal efficiency, simple operation, and low energy consumption. The A2O-wetland is a good alternative for rural wastewater treatment systems.