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Sustainability and optimisation of treatment and use of wastewater in agriculture

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Irrigating crop production with wastewater

The worldwide threat of fresh water shortages has compelled researches to investigate alternative water sources for the irrigation of agricultural crops. As such, utilising wastewater has gained considerable value, and initiating means by which this source of water can be used are being evaluated.

Climate Change and Environment

In order to tap wastewater sources and convert them into suitable forms for reuse, new treatment and irrigation technologies needed to be developed. Wastewaters carry biochemical, bacterial and faecal effluents that may pose serious health risks. As such, it was important to understand how effective Free Water Systems (FWS) were in removing harmful content from wastewater. Free Water Systems act like a natural filtering environment where water lies in a manmade wetland over a specified length of time. The water is purified through various natural environmental processes such as percolation and vegetation filtration. These processes reduce such factors as Total Suspended Solids (TSS), Biological Oxygen Demand (BOD) and Total Faecal Coliforms (TFC) as well as water's nitrogen and phosphorus levels. While FWS are effective, a new, low cost, epuvalisation tertiary treatment technique was developed. This technique aimed at sustainable water usage by recycling municipal wastewater effectively so as to allow its safe discharge back into the environment. Alternatively, the water treated could also be used for agricultural use, mainly for non-edible crops. Utilising the water produced from this system required investigation into the most appropriate irrigation methods that would best compliment recycled wastewater for agricultural use. The effects of wastewater on irrigation systems had to be understood. For example, integrated drippers with low sensitivity to physical clogging, tested in Tunisia, yielded the best results, providing optimum irrigation uniformity. Micro-aspersion and auto-regulated drippers on the other hand, showed the worst results due to their poor technological conception. Finally, to determine the effectiveness of the project it was important to evaluate the effects on soil and plant complexes that wastewater usage and irrigation methods produced. Overall, crop and plant growth performance was compatible to that of growth patterns when fresh or borehole water was used. Depending on the crop type and irrigation method used, growth performances were also significantly improved. As such, wastewater usage should, when correctly processed, recycled and applied, provide an acceptable alternative to using fresh water sources. Since the emphasis is on sustainable development, the technology goes a long way in improving agricultural practices to meet with these requirements.

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