Philip Amoah

Quantification of the health risk associated with wastewater reuse in Accra, Ghana: a contribution toward local guidelines

Quantitative Microbial Risk Assessment (QMRA) models with 10,000 Monte Carlo simulations were applied to ascertain the risks of rotavirus and Ascaris infections for farmers using different irrigation water qualities and consumers of lettuce irrigated with the different water qualities after allowing post-harvest handling. A tolerable risk (TR) of infection of 7.7 x 10(-4) and 1 x 10(-2) per person per year were used for rotavirus and Ascaris respectively. The risk of Ascaris infection was within a magnitude of 10(-2) for farmers accidentally ingesting drain or stream irrigation water; approximately 10(0) for farmers accidentally ingesting farm soil and 10(0) for farmers ingesting any of the irrigation waters and contaminated soil. There was a very low risk (10(-5)) of Ascaris infection for farmers using pipe-water. For consumers, the annual risks of Ascaris and rotavirus infections were 10(0) and 10(-3) for drain and stream irrigated lettuce respectively with slight increases for rotavirus infections along the post-harvest handling chain. Pipe irrigated lettuce recorded a rotavirus infection of 10(-4) with no changes due to post harvest handling. The assessment identified on-farm soil contamination as the most significant health hazard.

Influence of urban wastewater on stream water quality and agriculture in and around Kumasi, Ghana

This paper presents some findings from an ongoing International Water Management Institute research project in Ghana on urban wastewater use in agriculture. The paper focuses on the influence of urban wastewater on stream water quality and peri urban agriculture in Kumasi, and aims to develop strategies to reduce environmental pollution and risks from agricultural use of wastewater. It drew on interviews with local authorities, sanitation services providers, vegetable producers, traders and consumers, and on an assessment of the existing sanitation infrastructure and water quality. With few industries in Kumasi, urban wastewater is generated mostly from domestic sources. Population increase and lack of investment have overstretched the few available sanitation facilities, and large volumes of untreated or partially treated wastewater end up in nearby streams. High levels of faecal coliform were recorded in the city and downstream, as well as on vegetables in Kumasi’s markets, as contaminated wastewater streams are used for irrigation. Although urban and peri urban agriculture has a positive impact on food supply and livelihoods, it poses health risks for farmers and consumers. The paper discusses the constraints on addressing these problems and makes some recommendations regarding low-cost strategies for safer use of available water, better urban decentralized wastewater management and increased public awareness.

Effectiveness of common and improved sanitary washing methods in selected cities of West Africa for the reduction of coliform bacteria and helminth eggs on vegetables

Objective  To analyse and improve the effectiveness of common indigenous washing methods for the reduction of faecal coliform (FC) populations on the surface of wastewater‐irrigated vegetables and to determine simple factors affecting their efficacy.

Microbial Hazards in Irrigation Water: Standards, Norms, and Testing to Manage Use of Water in Fresh Produce Primary Production

Accessibility to abundant sources of high-quality water is integral to the production of safe and wholesome fresh produce. However, access to safe water is becoming increasingly difficult in many parts of the world, and this can lead to the production of fresh produce contaminated with pathogenic microorganisms, resulting in increased risk of human disease. Water, an important raw material in the fresh produce chain, is used in considerable amounts in many operations, including irrigation and application of pesticides and fertilizers, but also as a transport medium and for cooling and washing in postharvest practices. In several reported outbreaks related to uncooked fruit and vegetable products, water has been identified as a likely source of the outbreak. The present study, initiated by the ILSI Europe Emerging Microbiological Issues Task Force in collaboration with 8 other ILSI branches and support of WHO/FAO, was undertaken to review the status of, and provide suggestions for, consideration by different stakeholders on water and sanitation and its impact on food safety and public health. A limited number of guidelines and regulations on water quality for agricultural production are available, and many of them are still heavily based on microbial standards and (debated) parameters such as fecal coliforms. Data gaps have been identified with regard to baseline studies of microbial pathogens in water sources in many regions, the need for agreement on methods and microbial parameters to be used in assessing water quality, the fate of pathogens in water, and their transfer and persistence on irrigated/processed produce.

Reducing health risks from wastewater use in urban and peri-urban Sub-Saharan Africa: applying the 2006 WHO guidelines

Where rapid urbanization is outpacing urban capacities to provide sound sanitation and wastewater treatment, most water sources in city vicinity are heavily polluted. This is of great concern as many of the leafy vegetables eaten raw in the cities are produced in these areas. Following the new WHO guidelines, different non-treatment options at farm, market, and kitchen level were field tested for health risk reduction with special consideration to efficiency and adoption potential. As most households are used to vegetable washing (although ineffectively), an important entry point for risk reduction is the increased emphasis of the new guidelines on food preparation measures. A combination of safer irrigation practices (water fetching, on-farm treatment, and application), the allocation of farmland with better water sources, and improved vegetable washing in kitchens appear to be able to reduce the potential risk of infections significantly, although it might not be possible to reach the ideal threshold without some kind of wastewater treatment. The on-farm trials carried out in Ghana also explored the limitation of other risk reduction measures, such as drip irrigation, crop restrictions and cessation of irrigation under local circumstances considering possible incentives for behaviour change.

Quantification of human norovirus GII, human adenovirus, and fecal indicator organisms in wastewater used for irrigation in Accra, Ghana.

Quantitative microbial risk assessment (QMRA) is frequently used to estimate health risks associated with wastewater irrigation and requires pathogen concentration estimates as inputs. However, human pathogens, such as viruses, are rarely quantified in water samples, and simple relationships between fecal indicator bacteria and pathogen concentrations are used instead. To provide data that can be used to refine QMRA models of wastewater-fed agriculture in Accra, stream, drain, and waste stabilization pond waters used for irrigation were sampled and analyzed for concentrations of fecal indicator microorganisms (human-specific Bacteroidales, Escherichia coli, enterococci, thermotolerant coliform, and somatic and F+ coliphages) and two human viruses (adenovirus and norovirus genogroup II). E. coli concentrations in all samples exceeded limits suggested by the World Health Organization, and human-specific Bacteroidales was found in all but one sample, suggesting human fecal contamination. Human viruses were detected in 16 out of 20 samples, were quantified in 12, and contained 2-3 orders of magnitude more norovirus than predicted by norovirus to E. coli concentration ratios assumed in recent publications employing indicator-based QMRA. As wastewater irrigation can be beneficial for farmers and municipalities, these results should not discourage water reuse in agriculture, but provide motivation and targets for wastewater treatment before use on farms.

Zero Risk Does Not Exist: Lessons Learned from Microbial Risk Assessment Related to Use of Water and Safety of Fresh Produce

Risk assessments related to use of water and safety of fresh produce originate from both water and food microbiology studies. Although the set-up and methodology of risk assessment in these 2 disciplines may differ, analysis of the current literature reveals some common outcomes. Most of these studies from the water perspective focus on enteric virus risks, largely because of their anticipated high concentrations in untreated wastewater and their resistance to common wastewater treatments. Risk assessment studies from the food perspective, instead, focus mainly on bacterial pathogens such as Salmonella and pathogenic Escherichia coli. Few site-specific data points were available for most of these microbial risk assessments, meaning that many assumptions were necessary, which are repeated in many studies. Specific parameters lacking hard data included rates of pathogen transfer from irrigation water to crops, pathogen penetration, and survival in or on food crops. Data on these factors have been investigated over the last decade and this should improve the reliability of future microbial risk estimates. However, the sheer number of different foodstuffs and pathogens, combined with water sources and irrigation practices, means that developing risk models that can span the breadth of fresh produce safety will be a considerable challenge. The new approach using microbial risk assessment is objective and evidence-based and leads to more flexibility and enables more tailored risk management practices and guidelines. Drawbacks are, however, capacity and knowledge to perform the microbial risk assessment and the need for data and preferably data of the specific region. Practical Application This manuscripts intends to give an extensive overview of approaches and challenges of past and future quantitative microbial risk assessment studies in the fresh produce chain related to the use of water in order to aid further research efforts in this area.

A probabilistic model of gastroenteritis risks associated with consumption of street food salads in Kumasi, Ghana: evaluation of methods to estimate pathogen dose from water, produce or food quality.

With a rapidly growing urban population in Kumasi, Ghana, the consumption of street food is increasing. Raw salads, which often accompany street food dishes, are typically composed of perishable vegetables that are grown in close proximity to the city using poor quality water for irrigation. This study assessed the risk of gastroenteritis illness (caused by rotavirus, norovirus and Ascaris lumbricoides) associated with the consumption of street food salads using Quantitative Microbial Risk Assessment (QMRA). Three different risk assessment models were constructed, based on availability of microbial concentrations: 1) Water - starting from irrigation water quality, 2) Produce - starting from the quality of produce at market, and 3) Street - using microbial quality of street food salad. In the absence of viral concentrations, published ratios between faecal coliforms and viruses were used to estimate the quality of water, produce and salad, and annual disease burdens were determined. Rotavirus dominated the estimates of annual disease burden (~10(-3)Disability Adjusted Life Years per person per year (DALYs pppy)), although norovirus also exceeded the 10(-4)DALY threshold for both Produce and Street models. The Water model ignored other on-farm and post-harvest sources of contamination and consistently produced lower estimates of risk; it likely underestimates disease burden and therefore is not recommended. Required log reductions of up to 5.3 (95th percentile) for rotavirus were estimated for the Street model, demonstrating that significant interventions are required to protect the health and safety of street food consumers in Kumasi. Estimates of virus concentrations were a significant source of model uncertainty and more data on pathogen concentrations is needed to refine QMRA estimates of disease burden.

Temperature and deactivation of microbial faecal indicators during small scale co-composting of faecal matter

Small scale co-composting of faecal matter from dry toilet systems with shredded plant material and food waste was investigated in respect to heat development and deactivation of faecal indicators under tropical semiarid conditions. Open (uncovered) co-composting of faecal matter with shredded plant material alone did not generate temperatures high enough (<55 degrees C) to reduce the indicators sufficiently. The addition of food waste and confinement in chambers, built of concrete bricks and wooden boards, improved the composting process significantly. Under these conditions peak temperatures of up to 70 degrees C were achieved and temperatures above 55 degrees C were maintained over 2 weeks. This temperature and time is sufficient to comply with international composting regulations. The reduction of Escherichia coli, Enterococcus faecalis and Salmonella senftenberg in test containment systems placed in the core of the compost piles was very efficient, exceeding 5log10-units in all cases, but recolonisation from the cooler outer layers appeared to interfere with the sanitisation efficiency of the substrate itself. The addition of a stabilisation period by extending the composting process to over 4 months ensured that the load of E. coli was reduced to less than 10(3)cfu(-g) and salmonella were undetectable.

From world cafes to road shows: using a mix of knowledge sharing approaches to improve wastewater use in urban agriculture

This paper documents the application of several innovative knowledge sharing approaches and some of the lessons learnt in a project addressing food safety concerns deriving from wastewater irrigated vegetables in Ghana. Knowledge sharing activities received particular attention in the project to facilitate its impact pathway, in particular to (i) verify preliminary research messages on good practices, (ii) raise awareness and build capacity, and (iii) equip various stakeholder groups with knowledge, skills and materials. Key approaches and tools applied were the world café approach for the verification of research messages. The approach brought together farmers, traders and street food vendors to openly discuss proposed improvements in current practices and their potential for wider uptake. For target-oriented message dissemination multi-media training materials were prepared following recommendations from the intended users, like extension agents, catering and farmer field schools. The materials made use of local-language radio broadcasts, training and awareness videos, illustrated flip charts showing good and bad practices for wastewater use and improved teaching materials. Finally, for enhanced mutual learning so called road Shows were used to facilitate knowledge sharing between researchers, end-users, policy- and decision-makers. These allowed all stakeholders to follow the pathogen pathway from farm to fork while learning about the importance of well-identified intervention points and mutual responsibility. All applied approaches added significant value to the research work and facilitated its impact potential as first feedback shows. However, the applied tools do not come for free. They require careful preparations, the ability to listen and skillful facilitation.