Increasing costs for wastewater treatment provide incentives to evaluate system alternatives, especially among small communities with limited financial resources. Land treatment systems with hybrid poplar tree plantations are becoming increasingly popular as one such alternative in the Pacific Northwest. Land treatment systems are made up of a complex dual system: the wastewater treatment system and the poplar tree plantation. The complex dual system must account for temporal and spatial variability of natural systems. The goal of the system design is to optimize system parameters, after accounting for system complexity and variability, to maximize economic return without causing adverse effects on the environment and society. This study presents a system optimization model which accounts for the system complexity and natural variability. The model consists of three submodels: nitrogen loading rate estimation submodel, nitrate leaching submodel and total net revenue estimation submodel. The composite model identifies the maximum total net revenue and determines associated system design parameters. An optimization example for a hypothetical community with a population of 5,000 is presented. The optimal system with no time horizon or land area constraints is expected to return a net revenue of $773,659 over a 296-year project lifetime. The wastewater treatment system is characterized by the optimal nitrogen loading rate of 49 kgN/ha and the corresponding estimated leachate nitrate concentration of 8.80 mgN/L. The poplar tree plantation is characterized by the optimal rotation period of 8 years and the optimal total field size of 202 ha. Additional analysis indicates that total net revenue would not be positive if the design system lifetime was shorter than 60 years, or the maximum field size was smaller than 150 ha. Accounting for land depreciation due to wastewater application reduced the optimal nitrogen loading rate by 2 kgN/ha. Costs for an equity loan would reduce system profitability significantly. Sensitivity analysis demonstrated that the model was sensitive to nitrate leaching and poplar tree growth parameters. It was concluded that calibration for site specific nitrate leaching and poplar hybrid specific growth parameters should be evaluated to have more confidence in model performance. / Graduation date: 2004

Thesis (M. Sc.)--University of Western Sydney, Hawkesbury, 1991. / Includes bibliographical references.

Thesis (doctoral)--University of Lund, 1990. / "CODEN:LUTVDG/ (TVVA-90/1002)." Thesis t.p. inserted. Includes bibliographical references (p. 181-189).

No description available.

Increasing demands for improved water quality in receiving waters, effluent reclamation and reuse have prompted wide interest in the use of wetlands for the treatment of wastewater. Over a four year period, domestic sewage effluent was treated using a range of gravel based, subsurface flow constructed wetland systems. Weekly samples at inlet and outlet points were assayed for suspended solids, biological oxygen demand, organic carbon, total kjeldahl nitrogen, ammonium, nitrate/nitrite, phosphorus, dissolved oxygen, temperature, pH and faecal coliform levels. The wetland system received secondary treated effluent for three years and primary settled effluent for one year. The potential of constructed wetland systems for nitrogen removal and potential pathogen reduction was investigated. Nitrogen removal was characterised by estimation of potential nitrification and denitrification rates within the system. Disinfection performance of the wetland system was assessed by enumeration of faecal indicator bacteria in the system influent and effluent, as well as with distance along the length of the system. The removal rate was estimated, considering influent and effluent faecal coliform concentrations as well as system hydraulic retention time and temperature. / Master of Science (Hons)

The effectiveness of a cheap, low-tech, environmentally and technically favorable treatment of secondary treated municipal wastewater by contaminant removal through a floodplain-soil filter was evaluated using floodplain-simulating field lysimeters, packed with a sandy soil in 2002 and sand in 2003 and 2004. Secondary treated wastewaters from Vaudreuil (2002 and 2003) and Pincourt (2004) Wastewater Treatment Plants were used as influent. This was applied at rates of 0.06, 0.19, and 0.31 m3 m-2 d -1 to vegetated lysimeters, and at a rate of 0.19 m3 m-2 d-1 to bare-soil lysimeters. / Removal of NH4+-N, NO3--N, and COD from the influent was studied in all three years. Irrespective of flow rate or year, the system removed 62~84%, 96~99%, and 6~67% of TKN, NH4+-N, and COD, respectively, from the influent. Under 0.19 m3 m-2 d-1 flow rate, vegetated systems removed slightly more of these constituents from the influent, than did bare-soil lysimeters. Organic degradation mainly occurred in the top 0.1 m soil depth. Degradation of organic and inorganic influent nitrogen increased NO3--N levels in the effluent. Only minimal increases in soil-N levels and N2O emissions occurred with increasing application rates. The nitrogen mass balance accounted for 85∼98% (2003) and 67∼96% (2004) of input nitrogen (through leaching, soil retention, and N2O emissions), the remaining portion being attributable to vegetative effects and volatilization of non-N2O nitrogenous gases. The under established vegetation on the lysimeters reduced nitrogen leaching through soil, being 6% (2003) and 60% (2004) more effective than bare soil. / Effluent water quality improved with decreasing levels of heavy metals. Compared to influent levels, in vegetated lysimeters, under all flow rates, mean effluent As, Cd, Cu, Ni, Pb, and Zn levels had dropped by 58%, 9%, 3%, 37%, 63%, and 52% in 2003, and by 20%, 63%, 5%, 23%, 18%, 57%, and 79% for As, Cd, Cr, Cu, Ni, Pb, and Zn, in 2004. In both years, similar decreases in heavy metal levels occurred in the bare soil lysimeters. Across all flow rates and influent concentrations, soil heavy metal levels increased. In 2004, even low heavy metal content influent further increased (6∼179%) their accumulation in soil. As inputs of heavy metals to the soil increased with the increase in application rates, their associated times to reach maximum permissible limits also decreased. / LEACHN simulation of NO3--N in leachate arising from wastewater application, showed lowered levels with increasing flow rates, due to enhanced denitrification in the resulting anoxic upper soil zones. The simulation under continuous wastewater application at different range of nitrogen concentrations (low, medium, high) showed an increase of NO 3--N levels in the leachate with increasing N-levels. For all flow rates, and under tropical or humid conditions, the effluent NO 3--N levels remained below permissible limits for the low-N content wastewater applications. Intermittent applications, under all wastewater N-contents and flow rates, reduced NO3--N levels in the leachate by 51∼89% compared to continuous wastewater application, and permissible limits were not exceeded. Hence, wastewater with high levels of nitrogenous compounds, as occurs in most developing countries, could be treated by land under an intermittent application pattern, allowing a considerable reduction in nitrate pollution.

Thesis (M. S. - Soil, Water, and Environmental Science)--University of Arizona, 1998. / Includes bibliographical references (leaves 61-69).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 232-241). Also available via the Internet

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 78-86). Also available via the Internet.

Thesis (M. Env. St.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1992. / Photographs mounted in. Includes bibliographical references (leaves 91-96).