Evaluation Of Non-Treatment Interventions For Reducing Health Risks Associated with Wastewater Irrigated Spring Onions
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Date
2011-07-14
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Abstract
In Ghana, urban sanitation infrastructure is poor and only a small portion of the wastewater generated is collected for treatment. The bulk ends up in drains and nearby water bodies and is used by vegetable farmers for irrigation. The purpose of this study was to assess the effectiveness of using locally feasible non-treatment interventions such as good farming and handling practices through producer-consumer pathway to reduce contamination on wastewater-irrigated spring onions. Spring onion samples were collected between November and April, 2008 in the dry season and analysed for thermotolerant coliforms by the MPN (three tubes) technique and helminth eggs using the flotation sedimentation method. The Statistical Package for Social Scientists (SPSS) version 13.0 was used for testing the various statistical relationships between and within variables. The initial study tested the effectiveness of cessation of irrigation prior to harvesting, management of watering can irrigation to reduce contamination and determination of major source of contamination of spring onions at production site. Post-harvest feasibility study was also carried out to understand the current handling practices of spring onions by market women, which served as a guide to develop appropriate ones. Sanitizers (salt and vinegar solution) were also tested for their efficacy in decontaminating spring onions at the kitchen. Spring onion was tracked from farm, to the market, and to the kitchen and subjected to selected feasible interventions. Samples were taken before and after each non-treatment intervention treatment and their effectiveness assessed. The result of the study showed that, an average of 0.52 log units for thermotolerant coliforms and 0.06 helminth eggs per 100 g of spring onions were removed on each day of cessation of irrigation. This corresponded to an average daily loss of 0.15 kg fresh weight of spring onions. Decreasing watering heights, whether with watering cans perforated or not increased thermotolerant coliforms significantly since results showed that bulbs of spring onion harbou6red the major source of contamination. Survival of thermotolerant coliforms and helminth eggs was higher in spring onions stored in sacks and lower in those stored in baskets. At the market, washing of spring onion (whole plant) with water proved to be the best option for reducing both thermotolerant coliforms and helminth eggs. However, washing affected the firmness of spring onion leaves, and as a result washing only the bulbs in a bowl of water (8.5 litres) for two minutes, was selected as the easily adoptable intervention. Use of vinegar solution was a more effective sanitizer than salt solution at the kitchen. The sum of the individual log unit reduction for the different non treatment options assessed in the study equal to 5.07 (vinegar) and 5.0 (salt solution) log units for thermotolerant coliforms with 2.2 (vinegar) and 1.5 (salt solution) helminth eggs for vinegar and salt solution, respectively. The multiple barrier approach (tracking same stock of spring onions from farm to kitchen) study suggests that to prevent thermotolerant coliforms and helminth eggs contamination on spring onions, adequate pre-harvest protection against pathogen contamination and post harvest cleaning and disinfection strategies need to be employed.