Office for Environmental Programs - Theses
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ItemThe TDS content of treated wastewaters and how this impacts on the reuse of these wastewaters for irrigating crops: with particular reference to China and neighbouring countries( 2005)With the rapid growth of population, water shortage is becoming one of the major barriers for sustainable development of human society. Among various options to solve the problem, wastewater reuse is considered as an attractive way with great environmental and economical benefits. Worldwide, irrigation is a very common practice with regard to wastewater reuse. However, a major concern with the long-term application of treated wastewater in irrigation is the potential for salts to build up in the soil. With review of related literatures, this paper analysed the total dissolved salts in raw and treated wastewater and explained the potential salinity and sodicity hazards that they would cause. The formation of salinity and sodicity is a complex process that not only depends on the level of total dissolved salts but also relates to other factors such as weather conditions, crop selection, soil property, irrigation methods, legislation and field practice. Therefore, to maximise crop production and soil protection, it is necessary to adopt an integrated approach to manage crop irrigation using treated wastewater. And the implementation of the integrated approach will determine whether the reuse of treated wastewater is successful especially for countries that wastewater is directly used for crops irrigation without any protective procedures.
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ItemAn assessment of environmental risks of using recycled water to create environmental flows in the Werribee River, Victoria( 2004)Recycled water created from highly treated sewerage is now considered a viable water source for selected, appropriate uses. One potential use is to create environmental flows in stressed rivers if this is a low risk and low cost option. To evaluate these risks, a case study is investigated using the degraded Werribee River, Victoria. Environmental flows could be supplied to the river from the nearby Western Treatment Plant. Risks are identified using the judgement of river and water management experts and are evaluated using conceptual models and a Bayes network. Key risks investigated include risks to human health (gastroenteritis and arbovirsus infection) and risks to environmental health (blue-green algae blooms). Results show that these risks already exist to some degree but are unlikely to increase if recycled water is used to create environmental flows. While the creation of environmental flows with recycled water creates opportunities for health risks to increase, the risk is limited by low numbers of infected hosts. Blue-green algae risks are already high as the river currently exceeds nutrient guidelines. Adding more nutrients will not increase this risk and interestingly improving stream flows using saline recycled water will prevent blue-green algae accumulation, actually decreasing the risk.
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ItemImproving water quality through aquifer storage recovery( 2006)Aquifer Storage Recovery (ASR) is a technique used to store excess water in the sub-surface during periods of low demand for recovery during periods of high demand. Often, the excess water stored is treated effluent, and a secondary benefit of ASR is water quality improvement through reduction of disinfection-by products (DBPs) in this effluent. A review of published data from a number of ASR sites has found there are two processes dominating the DBP concentration of recovered groundwater from an ASR site: biodegradation of DBPs and DBP formation. Favourable conditions for biodegradation of DBPs are a redox environment that is highly reducing as well as the availability of sufficient dissolved organic carbon for microbial consumption. DBP formation during ASR can be reduced by limiting the organic carbon concentration and chlorine residual of the injected water.