Abstract
Sanitation by-products (i.e. greywater, human urine and toilet compost) reuse for agriculture presents an opportunity to enhance food security while overcoming water scarcity and fertilizers issues in developing countries. However, the risks to health from farmers and consumers’ exposure to pathogenic micro-organisms persistent in sanitation by-products has hindered their popularity in these regions. This study was conducted to apply a quantitative microbial risk assessment to estimate the annual risk probability of Salmonella infection associated with these sanitation by-products reuse for lettuce production and explore options for health risk reduction. Risk was performed a Monte Carlo simulation for farmers and consumers. The exposure routes were contaminated soil ingestion, urine/greywater/compost ingestion and lettuce consumption without washing. Results showed that the annual infection risks of Salmonella through ingestion contaminated soil associated with urine and compost were typical scenario: 9.04 × per-person-per-year (pppy) and 2.97 × pppy, respectively, are higher than the WHO benchmark (≤1.0 × pppy). Conversely, those contaminated from greywater were 6.83 × pppy are meet the WHO benchmark. On the other hand, annual risks through lettuce consumption fertilized with urine (1.20 × pppy) were less than the risks from compost (6.20 × pppy) and greywater (7.76 × pppy). Moreover, the annual risks of infection from greywater ingestion (1.77 × pppy) exhibits a much higher risk than that urine ingestion (6.20 × pppy) approximately two orders of magnitude, and which are higher than the WHO tolerable limit of risk. The risk assessment outcomes of using sanitation by-products to lettuce production should be promoted with proper awareness of the risk by farmers and consumers.
Highlights
Sanitation by-products have been recognized as potential resources for agriculture as nutrients and water irrigation
The results showed that the annual infection risks of Salmonella for worker farm ingesting involuntary soil contaminated with toilet compost are significantly higher than the tolerable limit of risk defined by the WHO (2006) as 10−6 pppy
The results present the low annual risks infection of consumer exposure to Salmonella, and which are below the threshold recommended by WHO (2006)
Summary
Sanitation by-products (i.e. greywater, human urine, and toilet compost) have been recognized as potential resources for agriculture as nutrients and water irrigation. The reuse of sanitation by-products for agriculture would be an attractive option for small scale farmers in poor regions, who suffer from limited irrigation resources and poor access to chemical fertilizers Among these resources, greywater is defined as wastewater generated from domestic activities such as dish washing, laundry and bathing, in contrast to black water, which is a mixing of feces, urine, and flush (Wiel-Shafran et al, 2006). The decline in crop production due to loss of soil organic component, erosion, and nutrient runoff has generated interest in the recycling of fecal sludge compost into soil nutrients Overall, it has been reported by many researchers that human excreta or/and fecal sludge compost can be used as organic fertilizers for growing crops and improve soil structure (Jamal & Fawad, 2019), while reducing the sanitation problem caused by the indiscriminate disposal of fecal sludge into the environment (Appiah-Effah et al, 2015)
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