John Blackwell

Wastewater irrigation and environmental health: Implications for water governance and public policy

Climate change is a large-scale and emerging environmental risk. It challenges environmental health and the sustainability of global development. Wastewater irrigation can make a sterling contribution to reducing water demand, recycling nutrients, improving soil health and cutting the amount of pollutants discharged into the waterways. However, the resource must be carefully managed to protect the environment and public health. Actions promoting wastewater reuse are every where, yet the frameworks for the protection of human health and the environment are lacking in most developing countries. Global change drivers including climate change, population growth, urbanization, income growth, improvements in living standard, industrialization, and energy intensive lifestyle will all heighten water management challenges. Slowing productivity growth, falling investment in irrigation, loss of biodiversity, risks to public health, environmental health issues such as soil salinity, land degradation, land cover change and water quality issues add an additional layer of complexity. Against this backdrop, the potential for wastewater irrigation and its benefits and risks are examined. These include crop productivity, aquaculture, soil health, groundwater quality, environmental health, public health, infrastructure constraints, social concerns and risks, property values, social equity, and poverty reduction. It is argued that, wastewater reuse and nutrient capture can contribute towards climate change adaptation and mitigation. Benefits such as avoided freshwater pumping and energy savings, fertilizer savings, phosphorous capture and prevention of mineral fertilizer extraction from mines can reduce carbon footprint and earn carbon credits. Wastewater reuse in agriculture reduces the water footprint of food production on the environment; it also entails activities such as higher crop yields and changes in cropping patterns, which also reduce carbon footprint. However, there is a need to better integrate water reuse into core water governance frameworks in order to effectively address the challenges and harness the potential of this vital resource for environmental health protection. The paper also presents a blueprint for future water governance and public policies for the protection of environmental health.

Water quality monitoring using Landsat Themate Mapper data with empirical algorithms in Chagan Lake, China

Lake Chagan represents a complex situation of major optical constituents and emergent spectral signals for remote sensing analysis of water quality in the Songnen Plain. As such it provides a good test of the combined radiometric correction methods developed for optical remote sensing data to monitor water quality. Landsat thematic mapper (TM) data and in situ water samples collected concurrently with satellite overpass were used for the analysis, in which four important water quality parameters are considered: chlorophyll-a, turbidity, total dissolved organic matter, and total phosphorus in surface water. Both empirical regressions and neural networks were established to analyze the relationship between the concentrations of these four water parameters and the satellite radiance signals. It is found that the neural network model performed at better accuracy than empirical regressions with TM visible and near-infrared bands as spectral variables. The relative root mean square error (RMSE) for the neural network was < 10%, while the RMSE for the regressions was less than 25% in general. Future work is needed on establishing the dynamic characteristic of Chagan Lake water quality with TM or other optical remote sensing data. The algorithms developed in this study need to be further tested and refined with multidate imagery data

Evaluation of a sequential biological concentration system in natural resource management of a saline irrigated area

Abstract Wastewater need not be disposed to an evaporation basin until all useful benefit has been extracted from the waste stream. Sequential Biological Concentration (SBC) of saline drainage streams offers the ability to create a number of financial opportunities, whilst concentrating the waste stream to a manageable volume. In this paper, we present field data from the first three cells of a six-cell SBC system, to evaluate the potential for sustainable management of saline drainage on irrigated lands. The field data indicate that the progressive increase in salinity can be accommodated by using suitable cropping choices, although yields and hence financial returns could be smaller in the cells with the highest salinity water applications. Significant reductions in other pollutants were achieved during flow through the first cell of the SBC system, with appropriate irrigation and drainage management. In the SBC system we are motivated to grow the highest value crops at the different salinities, provided that adequate yields are maintained. Crop yield levels were maintained up to stage 2 which was irrigated with 3.6 dS/m water, but declined to about half in stage 3 when irrigated with 10.8 dS/m water. Changes in soil profile salinity show that a saline soil was progressively ameliorated due to leaching of the excess salts through provision of a subsurface drainage system and irrigation with 1.2 dS/m water. The SBC stage 1 soil salinity changes were very marked during leaching in the first two years, and very gradual in the subsequent years. A similar pattern of soil salinity changes was observed in the other SBC stages. An advantage of the FILTER type systems over traditional land-based sewage treatment is that the FILTER system can operate without building up salt in the soil profile, and thus ameliorate previously salinised sites not considered suitable for irrigated cropping. The performance of the last three cells of the proposed SBC system has been successfully tested in Australia and overseas. This SBC system with suitable modifications could potentially be used to handle saline drainage from other sources in Australia, such as dry land and urban areas.