The aim of this project was to identify a suitable solution to the problem of landfill leachate at the North Katoomba landfill site. Options were affected by a range of constraints including economics, location and the intrusion of ground water into the landfill. The initial goal was to contain and treat the leachate on site, with the eventual target to discharge into the nearest receiving waters. A constructed wetland option was devised and researched, involving identification of the major pollutants contained within the leachate, developing a concept design and estimating the likely removal efficiencies expected. Investigations identified the primary pollution parameters as microbial and nutrients. Metals were found to be low in concentration although the wetland has the capacity to deal with these pollutants should they become part of the pollution plume. A bench scale constructed wetland system was developed to give an indication of the removal efficiencies. The results suggest that a constructed wetland system would be appropriate for treating landfill leachate at the North Katoomba site. It is recommended that a constructed wetland be established in the field to determine the long term treatment prospects and the potential management problems in a practical application. / Master of Science (Hons)

Bibliography : leaves [34]-[40]

Graduation date: 1994

The risk of the Iraq’s marshlands disappearing is still high unless serious measures are adopted. Sewage discharge and irrigation-water pressure, compounded by the effects of climate changes and the extent of the planned dam construction in upstream countries, make this event more likely. Most of the marshlands’ inhabitants (Marsh Arabs) are suffering from lack of access to safe, clean water and lack of sanitation and are reluctant to look for better places to live and work. Constructed wetlands are among the best alternatives to solve their problems. The application of constructed wetlands to meet more stringent standards for wastewater reuse in agriculture contributes to mitigating the wastewater impact and irrigation pressure on the marshland ecosystem. It is here proposed that a 3.6 ha free-surface flow wetland  could manage the more stringent standard for reuse (15 mg/l) for BOD5 and TSS. A monitoring programme should nevertheless be associated with this kind of project to minimize health risks that may arise as a result of implementation. Despite the absence of studies that deal with wastewater reuse in irrigation projects at the national level (in Iraq), similar studies worldwide provide evidence of reuse possibilities. Furthermore, a performance requirements framework for wastewater reuse in irrigation projects such as the one suggested by Biswas, draws an approach to meet sustainable development indicators and would likely contribute to support and encourage the Marsh Arabs to settle back in their own areas.

The polluted agricultural wastewater, after reaching marine recipients, can cause eutrophication. This problem can be tackled and mitigated by using constructed wetlands as water treatment systems. The fact that constructed wetlands work through long periods of time has led many scientists to evaluate how long they can still treat their influents effectively. The development and growth of vegetation and the accumulation of nutrients on the soils in a wetland are expected to occur. These processes change the wetland efficiency to remove pollutants. In this study, a set of wetlands constructed to treat agricultural wastewater were analyzed in different periods to assess if there is a difference in removal efficiency of nitrogen and phosphorus. This assessment was performed by analyzing the retention rate, k and k20 values, which are variables that quantify the nutrients removal, in different periods of each employed wetland. Some of the observations demonstrated differences when comparing different periods of the wetlands. The nitrogen removal presented better performance in one of the employed wetlands when this was older. Another employed wetland has not shown a clear difference between different periods. In the wetlands with high vegetation densities, the nitrogen removal was more stable over consecutive years. The occurrence of oscillations in nitrogen removal was observed more often in the wetlands with the highest vegetation densities over consecutive years. The phosphorus removal presented no clear differences between different periods. The results suggest that the removal of nitrogen improves after wetland creation due to the growth of vegetation. In addition, they suggest that wetlands with high vegetation densities tend to oscillate the nitrogen removal more or less often according to the density of the vegetation due to the balance between denitrification and decomposition. Further, the results suggest that the removal of phosphorus remains unchanged over longer periods than the periods considered in this study (four to six years) due to the deposition of organic matter on the soils.

Eight agricultural catchments in south Sweden were investigated for factors that may affect phosphorus (P) load and retention in the downstream situated wetlands (WL). P load is known to affect retention, and is determined by hydrological and geographical catchment characteristics. The wetlands were small (0.02-0.88%) in relation to their catchments (CA) and varied in design. Net sedimentation and P retention was determined with sedimentation plates during one year. The variables that best explained differences in particles and TP retention were the hydraulic load (q), TP load and the wetland length to width ratio. Contrary to expectations there was no correlation between factors that could be associated with erosion (i.e. slope and soil clay content) and retention of neither particles nor TP. Generally, the highest amounts of settled particles and P were found close to the wetland inlets, but soil disturbance (i.e. tillage) and high q increased the settling distance. It was likely that the smallest clay particles were too unaggregated to settle within these wetlands. Factors not included, such as wetland vegetation and bioturbation may have a large impact on P retention and this should be further investigated. The study also points to the difficulties in scaling down geological and P loss data from a regional to a local scale, as there can be large local deviations from the regional standard values. An easy method for identification of local “hotspots” for P losses should be of value for planning the location of future wetlands.

Upflow anaerobic sludge blanket (UASB) has been developed and commercially used for treating high-strength wastewaters since 1971, and this process has been extended its applications to domestic sewage treatment since 1980. Constructed wetlands (CWL) can be treated as a simulated natural treatment system, which use solar radiation as the energy source. By analogy with some removal mechanisms in natural wetlands, constructed wetlands are able to transform and remove pollutants from the wastewater. Other features provided by the constructed wetland include wildlife support, hydrologic modification, erosion protection, and open space and aesthetics. It has been applied for domestic wastewater purification for decades. In this study, a pilot UASB-CWL reactor was built to test its performance for the removal of organic compounds and nutrients from a sewage with COD (Chemical oxygen demand) in the range of 200-300 mg/L. The UASB reactor has an active liquid volume of 2.5 liters and the CWL includes a 56 L-tank (CWL-1) followed by a 80 L-tank (CWL-2) in which emergent macrophyte (reed, Phragmites australis L.) and floating macrophyte (Pistia stratiotes L.), respectively, were planted. Effects of hydraulic retention time (HRT) of the test water in the reactor on the pollutant removal were tested. Results indicate that with HRTs of 2, 45, and 64 hours, respectively, in the UASB, CWL-1, and CWL-2, the system exhibited good performances for pollutant removal. The HRTs are equivalent to CODt loadings of 3.06, 0.065, and 0.026 kg/m3.day to the UASB, CWL-1, and CWL-2, respectively. Average total COD (CODt), soluble COD (CODs), total biochemical oxygen demand (BODt), suspended solids (SS), and phosphate-P (P) were 121, 62, 33, 130, and 0.10 mg/L, respectively, and these are equivalent to the removal efficacies of 45-65, 60-80,65-75, 30-50, and 85-95%, respectively. With the operation conditions, average CODt = 28 , CODs = 18, BODt = 10, SS = 18, NH3-N = 18, NO2--N =12 , NO3--N = 1.0, and P = 0.0 mg/L were obtained, and the average removal total efficacies were 93, 93, 90, 75, 72, 95, and 100%, respectively. Effluent qualities are far superior to the national effluent standards for domestic sewage in Taiwan.

In most cases, data from petroleum industry wetland studies indicate that treatment wetlands are equally or more effective at removing pollutants from petroleum industry wastewaters than from other types of wastewater. In this study, we discussed the treatment efficiencies of oil-refinery industry wastewater by pilot-scale constructed wetland systems .The constructed wetland systems were one free water surface system filled with the sandy media and one subsurface flow system filled with the gravel media operated in parallel. Each system planted with Phragmites communis. The hydraulic retention time for the treatment wetland was controlled in turn at 0.96, 0.48, and 0.72 days. The experimental results showed that all of these contaminants could be reliably removed from wastewater by treatment wetland, especially the FWS. The effluents from the constructed wetland systems reusing and recovering were feasible.

Thesis (M.E.S.)--The Evergreen State College, 2004. / Title from title screen (viewed 3/11/2010). Includes bibliographical references (p. 139-150).

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