Optimal bed thickness and effective size for improving wastewater quality for irrigation
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ORIGINAL RESEARCH
Optimal bed thickness and effective size for improving wastewater quality for irrigation Godwin King‑Nyamador1 · Peace Korshiwor Amoatey1 · Samuel Amoah1 · Benny Adu‑Ampong2 Received: 6 August 2020 / Accepted: 24 October 2020 © Islamic Azad University 2020
Abstract With the increased use of wastewater for irrigation, there is the need to reduce the contaminant levels in wastewater. The slow sand filtration (SSF) is one such method that can be used to improve wastewater quality. However, the treatment quality depends among other factors on the depth of sand bed and the effective size. Acquiring sand of a particular effective size is becoming increasing difficulty and, therefore, this study sought to investigate over a specified area, the optimal depth and effective size that will be able to get rid of contaminants in wastewater. In separate experiments, three depths (30 cm, 40 cm and 50 cm) and two effective sizes (0.27 mm and 0.45 mm) were set up to investigate their effectiveness in removing Faecal coliform, E. coli and heavy metals (Pb, Cu and Fe) for wastewater from a peri-urban drain used for irrigating vegetables. Results showed that a minimum sand bed thickness of 40 cm and an effective size of up to 0.45 mm reduced the contaminants tested significantly, wastewater from the drain can be treated. It must be mentioned that the finer sand (0.27 mm) had a slightly better removal efficiency. This implies that the extra cost of acquiring sand of relatively smaller effective size and a higher bed depth with the aim of improving wastewater quality can be saved. Further investigations are being carried out on the combined effects of the optimal sand bed depth and effective size. Keywords Bed depth · Effective size · Kawukudi · Slow sand filter · Wastewater irrigation
Introduction Water, the most common liquid on earth covering about three-quarters of the earth’s surface is essential for the survival of all living things. Despite its valuableness to life, it is increasingly becoming a scarce resource in many arid and semi-arid countries [1]. It is used by humans in many ways such as drinking, domestic use, industrial use and agricultural irrigation. Agriculture is the largest consumer of the earth’s fresh water of about 42% [2]. Wastewater is any water used either domestically or industrially and contains waste materials or substances. It was defined by Raschid-Sally and Jayakody [3] as a combination of domestic effluents (consisting of black and grey water), effluents from commercial establishments (like * Peace Korshiwor Amoatey [email protected]; [email protected] 1
Department of Agricultural Engineering, University of Ghana, P. O. Box LG 77, Legon, Accra, Ghana
Department of Agricultural Engineering, KNUST, Kumasi, Ghana
2
hospitals), industrial effluents (where present) and stormwater from runoff. The composition of wastewater is dependent on the uses to which the water was put and may contain a variety of pathogens and other contaminants such as bacteria, viruses, protozoa
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