Performance evaluation of sub-surface flow constructed wetland systems under variable hydraulic loading rates

Wastewater treatment has given an immense attention in the field of pollution control throughout the world. This has become a challenge in developing countries due to the limitations of resources and expertise. Constructed wetlands where water, plants and microorganisms interact to improve the quality of water have been proven to be an effective low-cost wastewater treatment technology in many parts of the world, which does not necessarily require skilled personnel to run the system. However, these systems are not yet widely spread in developing countries due to lack of information. Constructed wetlands can be designed as surface flow or subsurface flow systems, depending on the level of the water column. This study compares the performance of vertical subsurface flow (VSSF) and horizontal subsurface flow (HSSF) constructed wetland systems at laboratory scale at tropical condition. This paper also evaluates the effects of Hydraulic Loading Rate (HLR) on treatment capacity of wastewater parameters such as Five day Biochemical Oxygen Demand (BOD5), Total Suspended Solids (TSS), Nitrate Nitrogen (NO3 —N), Phosphate (PO4 3-), Ammonia Nitrogen (NH4-N ), Fecal Coliforms (FC) and Total Coliforms (TC). Six wetland models of size 1.4 m x 0.5 m x 0.5 m (L x W x H) were constructed and arranged: 1) Two models as VSSF system with plants, 2) Two models as HSSF system with plants, 3) One model as a VSSF control without plants and 4) One model as a HSSF control without plants. An emergent macrophyte specie; cattail (Typha angustifolia), gravel media (size 10 – 20 mm) and synthetic wastewater with average concentrations of BOD5 ; 29.51 ± 4.21 mg/L, NO3 - - N ; 3.22 ± 1.25 mg/L, NH3 - - N ; 15.14 ± 2.65 mg/L, PO4 3- ; 6.78 ± 5.67 mg/L, Fecal Coliform 495.12 * 103 ± 307.12 * 103 counts/100 mL and Total Coliform 915.5 * 103 ± 719.83 * 103 counts/100 mL were used in this study. The HLR was increased from 2.5 – 25 cm/day at 12 days interval during two and a half months period. Sampling was carried out with each HLR from both influent and effluents of each wetland system after 12 days of constant flow rate, and wastewater quality parameters such as the BOD5, TSS, NH4-N, NO3 --N, PO4 3-, pH, Conductivity, FC and TC were measured in all samples. Results show that VSSF systems perform better than horizontal systems, but the treatment performance declines with the increasing HLR in all six wetland models

A statistical approach for landfill classification in Sri Lanka based on waste characteristics

Several parameters have been used to characterize wastes in dumping sites. It is not possible to measure all the parameters and also those parameters are not equally important for management options which are decided on priority basis. In fact some parameters are closely related to other parameters. Therefore, parameters have to be clustered for classifying the wastes in dumping sites. A study was conducted to develop a statistical procedure using available tools to cluster landfills based on landfill waste characteristics. Five waste samples were collected from three landfills in the central province of Sri Lanka to compare the waste characteristics followed by the use of data to elaborate the clustering procedure. Correlation diagrams, principle component and cluster analysis have been applied for eight parameters; Moisture content, Ash content, Unit Volume mass, Lower heating value, Particle density < 2mm, Plasticity index, pH and Electrical Conductivity. Statistical analysis was able to extract two main principle components as primary, and secondary which accounted for 92.1 % of the total variability establishing two main classes which can be further improved to be more representative and precise with the increased number of samples subjected to the analysis

Investigation of landfill suitability based on semi quantitative risk matrix and GIS

Open dumping is the most widely practiced method in Sri Lanka to dispose municipal solid waste (MSW) because it is the cheapest and easiest method compared to other methods available to manage MSW.Currently, there are no guidelines available for a proper selection of landfill dump site which may minimize the environmental, social and economic problems in the country. Site selection for landfill sites is an important aspect from both environmental conservation and social/economical point of view. Data was collected from the Udapalatha area for analyzing. Considering priority of all criteria in comparison with others, a specific risk rate was decided to each criterion according to their total influence on the whole process of decision making. Suitable landfill site was analyzed by using the Geographic Information System (GIS) together with risk assessment. To identify appropriate landfill areas in the study area, five input map layers including surface water bodies, distance from transportation routes, distance from urban areas, land use/land cover, and elevation were used in the mapping. Based on these data a risk assessment wascarried out with a semi-quantitative matrix. The findings obtained from this study could be used for preliminary information to develop criteria for new landfill site selection. Finally, suitable low-risk regions in the area have been proposed for solid waste landfill disposal

Physico-Chemical Characteristic of a Petroleum Contaminated Soil from the Spill site of Jaffna District.

Contamination of soil with petroleum products is among the most common sources of pollution in an industrialized world. This poses severe threats to the local communities and the ecosystem. Consequences of soil contaminations by petroleum products are multi-dimensional and thus their assessment has remained major problem. The presence of total organic carbon (TOC), heavy metals, electrical conductivity (EC) and pH were determined from petroleum contaminated soil samples from the spilled location of power plant premises of Chunnakam, Jaffna district. Three spilled locations have been identified and samples were collected from each location for this study. Control samples were collected from the uncontaminated location from the area same as the geology of the affected area. Results revealed that the heavy metal content of lead and nickel were higher than those of the control site and the recommended permissible limit. Evidence of severe hydrocarbon contamination was confirmed by presence of elevated level total organic carbon in the contaminated soil. Other analyzed metals including ferrous and manganese and physical parameters such as electrical conductivity and pH in the impacted zone have not shown any significant differences, while compared to the control samples