K. Mathew

Development of a reliable low-cost reverse osmosis desalination unit for remote communities

Research was carried out for two years to investigate the potential of using renewable energy pumped reverse osmosis (RO) for ground water desalination in remote Aboriginal communities of Australia. This has resulted in the development of a prototype pilot scale, low-pressure, wind-powered RO system. This paper presents the prototype design, construction and field testing to determine the quantity and quality of desalinated water produced and the reliability of the prototype operating under field conditions. Conclusions are drawn as to the operating requirements for use with typical Western Australian ground waters and in the Aboriginal community setting.

Integrated waste management

The concept of integrated waste management (IWM) has been developed to provide a means towards sustainability. Population growth coupled with increasing consumption have increased the amount of waste generated across the world while also facilitating the use of IWM to divert waste from landfill toward more long-term sustainable options such as reuse and recycling programmes — programmes that also maintain the longevity of a products life and reduce pressure on natural resources (Figure 26.1) (Ami et al., 2002). The other major factor influencing the formation of IWM strategies is social pressure Huang et al., 2001), Social pressure has been found to cause authorities to implement IWM strategies even where landfill space is available Barth. 2000) and has originated with increased education levels among consumers about current unsustainable and sustainable waste practices (Clarke et al., l99; Huang et al., 2001). The success of IWM strategies is largely attributed to the degree of social acceptance, such that the landfill problem associated with high population density areas has been found to stem from a low social acceptance of reuse and recycling programmes, rather than their absence (Ami et al.. 2002; Bradshaw and Ozores-Hampton, 2002: Mohee, 2002: Poon et al., 2001). An assessment of the social acceptance of IWM strategies is now a precursor for most new programmes and the technologies chosen for 1W M may he dependent on social factors (Kwawe, 2002).

The role of the submergent macrophyte Triglochin huegelii in domestic greywater treatment

Conventional reedbed systems, which are used in wastewater treatment, are little more than monocultures of Phragmites, Baumea, Water Hyacinth (Eichhornia crassipes), Typha or Schoenoplectus. Pond systems, employing a wider range of species, are a means to recycle more nutrients, improve treatment potential and mirror natural ecosystems in ways to sustain the ecosystem. Species of Triglochin, commonly known as water ribbons throughout coastal Australia, are fast-growing submergent macrophytes which seem to be adapted to high nutrient concentrations. In Western Australia, Triglochin huegelii is mainly a submergent plant but its leaves tend to float on the surface in shallow waterways and it has been found seasonally in some ephemeral swamps and lakes. As water receedes, the leaves become emergent. Initial studies using T. huegelii in wastewater treatment experiments has shown that Triglochin has consistently higher concentrations of nitrogen and phosphorus than Schoenoplectus validus, an emergent commonly used for wastewater nutrient stripping, in all parts of the plant - leaves, tubers and roots. In some cases, such as in the leaves, twice as much nitrogen and one and a half times more phosphorus is assimilated in the Triglochin tissue. It is also likely that T. huegelii will remove nitrogen and phosphorus at a greater rate than many other types of aquatic macrophytes. The implication is that instead of only planting the perimeter of lagoons, artificial wetlands and constructed basins we should be planting the bulk of the waterway with submergent species such as Triglochin spp. which may be far more effective in stripping nutrients than emergents currently used for that purpose.

Nitrogen and phosphorus removal from sewage effluent in amended sand columns

Column experiments were conducted to examine the removal of phosphorus and nitrogen from sewage effluent by passage through sand amended with bauxite refining residue (red mud). Red mud was neutralized with 5% gypsum. The study was conducted in two parts. In Part 1 the removal of nitrogen and phosphorus in mixtures of 30, 20 and 10% red mud in sand was compared. Cycles of 10 days flooding with secondary effluent and 18 days drying were used. An average of 24% nitrogen removal was obtained with 30% red mud, 9% removal with 20% red mud and very little removal with 10% red mud. An average of 91% phosphorus removal was obtained with 30% red mud, 63% removal with 20% red mud and 50% removal with 10% red mud. The decrease in phosphorus and nitrogen removal with decreasing red mud content was caused by a decrease in the adsorption capacity of the soil and an increase in the infiltration rate. In Part 2 the use of primary and secondary effluents was compared. Phosphorus removal was excellent using both primary and secondary effluents in columns packed with 30% red mud. Nitrogen removal continued to be poor using secondary effluent (16%) but was significantly greater using primary effluent (74%).

Leachate quality from gypsum neutralized red mud applied to sandy soils

Mixtures of fine bauxite refining residue (red mud), waste gypsum and local sandy soil that are proposed to be used in a catchment nutrient management program, were watered in columns simulating rainfall over a period of 2 yr and the quality of the leachate determined. The major salts released were sodium sulphate, a product of red mud alkalinity neutralization by gypsum, and excess gypsum released at its solubility concentration. At an application rate of 850 t ha−1 of red mud the salts leached to groundwater (40 kg t−1 red mud) would be equivalent to salts leached by rainfall over a 20 yr period from soil without red mud application, and would pose no significant impact when applied to the sandy agricultural soils in the catchment area of an estuary. The leaching of Al, Fe, and Cd from the red mud and gypsum was negligible, while the retention of superphosphate was over 99%. Fluoride from the waste gypsum was leached rapidly and reduced to background concentration (less than 1 mg L−1) within one winter rainfall.

The Comparison of Three Types of Indonesian Solar Box Cookers

This paper describes the influences which govern solar box cookers: HS 7534, HS 7033 and the newest design HS 5521. The best of solar cooker, type HS 7033 gave oven temperature of 202°C between 12:00 and 12:45 p.m. on October 7, 1997. Thirty-four units of this type have been field tested since September 1997. It was found that these solar cookers have a good heat storage capability, therefore they can be used for consecutive cooking. The optimization of the size, the aperture area, the insulator thickness, the oven volume and the reflector area leads to a new design, type HS 5521. Its volume is only 35% of the volume of HS 7033 and cheaper. The performance comparison of the last two solar cookers are described based on the data collected during testing with and without load. The HS 5521 has the same heat collection rate and is able to cook as fast as HS 7033.

Desalination using renewable energy in Australia

The history and performance of renewable energy driven desalination plants in Australia are reviewed. Included are the 3 500 m2 of solar stills built in South Australia in 1966, the two small scale photovoltaic reverse osmosis (RO) plants currently operating in Central Australia, a larger containerised photovoltaic RO plant from Western Australia, a Wind Powered RO Plant in Shark Bay, Western Australia, and two experimental Windmill powered RO plants designed at Murdoch University.

Groundwater recharge of sewage effluent through amended sand

Abstract The performance of a groundwater recharge basin at the Kwinana Groundwater Recharge Site in Western Australia was monitored between 1983 and 1986. A primary aim of the monitoring programme was to study the improvement in the removal of faecal coliforms and nutrients (nitrogen and phosphorus) by amending the sand of the recharge basin with gypsum-neutralized red mud (fine bauxite refining residue). The study consisted of five operating stages. Stage 1 was a baseline study using unamended sand. Stages 2–5 were after sand amendment with red mud. Continuous flooding and flooding/drying regimes were studied with primary effluent or a mixture of primary and secondary effluents. Phosphorus removal was maintained at a high level (over 80%) in all of the stages after the sand amendment. Faecal coliform removal was generally excellent, except at the beginning of each stage when primary effluent was used, and only a thousand-fold reduction was achieved. Removal improved with time and most monitored bore samples contained no faecal coliforms/100 ml. With one exception the groundwater met water quality criteria for irrigation. Nitrogen removal of approx. 45% was obtained with primary effluent using a cycle of flooding and drying (stage 3). Continuous flooding with primary effluent (stage 5) did not improve denitrification. No nitrogen removal was observed with a mixture of two-thirds secondary effluent and one-third primary effluent.

H2S paper strip method – a bacteriological test for faecal coliforms in drinking water at various temperatures

Epidemics arising from waterborne diseases are a global health problem. Faecal contamination of drinking water is the main cause of these outbreaks. According to WHO (1996) for drinking water to be safe, a 100 ml sample should not contain any coliform bacteria. The standard methods currently used for routine testing have many limitations especially when applied in remote areas. The H2S method has been developed as an on-site, inexpensive and easy to use method to test drinking water for remote and rural areas. The present work analyses the reliability of the H2S method for detecting faecal contamination in drinking water. The minimum level of faecal coliforms that could be detected and the incubation period required at various levels of contamination were studied. The range of temperatures at which the method was effective and the incubation period required at various temperatures were also determined. The H2S method was found to be able to detect contamination down to a level of 1 CFU/100 ml of coliform bacteria. Although the H2S method could be used at a temperature range of 20 to 44oC, temperatures between 28 to 37oC gave faster results. An incubation period of only 24 hours was required at 37oC, which was found to be the most suitable incubation temperature. The incubation period increased with a decrease or increase in temperature.

Greywater treatment with the submergent Triglochin huegelii—a comparison between surface and subsurface systems

Initial studies using Triglochin huegelii, a Western Australian species, in wastewater treatment experiments have shown that Triglochin has consistently removed more nitrogen and phosphorus, in all parts of the plant leaves, tubers and roots, than most other indigenous emergent macrophyte species. Our recent results have again shown that these types of plants do effectively assimilate nutrients from greywater. There was an increase in total N and total P in biomass measurements of T. huegelii leaves, roots and tubers during the course of the investigation. Sixteen percent of the greywater input N and 3% of input phosphorus was incorporated in plant tissue. Two further experiments were conducted using different environmental conditions for the plants. A comparison was made between root zone and complete pond conditions, with loading rate and retention times both doubled in some tanks. We found that more nutrients were absorbed by the plants in the pond system, with greater differences in nitrogen levels in the leaves (x 2) than in under-ground roots and tubers (x 1.6). Plants in ponds with the highest nutrient loading (10 1 tanks) demonstrated the greatest growth and nitrogen gain, while tanks having the longest retention time (5 1 tanks) had proportionally more N and P retention.