Pathogen and heavy metal contamination in urban agroecosystems of northern Ghana: Influence of biochar application and wastewater irrigation.

The benefit of biochar as a soil fertility enhancer is well known and has been broadly investigated. Equally, many tropical and subtropical countries use wastewater for irrigation in urban agriculture. To assess the related health risks, we determined pathogen and heavy metal fate associated with biochar application and wastewater irrigation in the urban agriculture of northern Ghana. Rice (Oryza L.) husk biochar (20 t ha-1 ), N-P-K 15-15-15 fertilizer (212.5 kg ha-1 ), and their combinations were evaluated in a field-based experiment. Untreated wastewater and tap water served as irrigation water. Red amaranth (Amaranthus cruentus L.) was used as a test crop and was grown in wet (WS) and dry (DS) cropping seasons. Irrigation water, soil, and vegetables were analyzed for heavy metals, Escherichia coli, fecal coliform, helminth eggs, and Salmonella spp. Unlike the pathogens, analyzed heavy metals from irrigation water and soil were below the FAO/WHO permissible standard for agricultural activities. Wastewater irrigation caused E. coli concentrations ranging from 0.5 to 0.6 (WS) and from 0.7 to 0.8 (DS) log10 colony forming units per gram fresh weight (CFU gFW -1 ) on vegetables and from 1.7 to 2.1 (WS) and from 0.6 to 1.0 (DS) log10 CFU per gram dry weight (gDW -1 ) in soil. Average log10 CFU gFW -1 rates of 6.19 and 3.44 fecal coliform were found on vegetables, whereas in soil, 4.26 and 4.58 log10 CFU gDW -1 were observed in WS and DS, respectively. Helminth egg populations were high in wastewater and were transferred to the crops and soil. Biochar did not affect bacteria contamination. Pathogen contamination on vegetables and in soil were directly linked to the irrigation water, with minimal or no difference observed from biochar application.

Impacts of four ionic liquids exposure on a marine diatom Phaeodactylum tricornutum at physiological and biochemical levels.

With the increasing applications in various industrial areas, toxicity of ionic liquids (ILs) has gained much attention in recent years. In this work, 1-octyl-3-methylimidazolium nitrate ([C8mim]NO3), 1-octyl-3-methylimidazolium chloride ([C8mim]Cl), N-octyl-3-metylpyridinium chloride ([C8mpy]Cl) and N-octyl-3-metylpyridinium bromide ([C8mpy]Br) were used to investigate the impacts of different types of cations and anions on their toxicity to a marine diatom Phaeodactylum tricornutum. Results showed that the four ILs had poor degradability under the culture conditions used in this study, and significantly inhibited the growth of this diatom with 96-h EC50 values of 24.0, 33.6, 16.1 and 14.4mgL-1 for [C8mim]NO3, [C8mim]Cl, [C8mpy]Cl and [C8mpy]Br, respectively. The data indicated that types of cations and anions would affect the toxicity of ILs to this diatom. Additionally, photosynthesis of this diatom was inhibited because significant decrease of chlorophyll a content and damage of PSII reaction centers were observed when it was exposed to the four ILs. Remarkable physiological and biochemical responses occurred in the cells of this diatom to alleviate the damaging effects of the four ILs. For example, content of soluble protein and activities of superoxide dismutase (SOD) and catalase (CAT) in the cells of this diatom increased significantly to form a protective mechanism against the toxicity of ILs, although they decreased in the cultures with high concentrations of ILs (≥20mgL-1). Thus, these results would not only provide strong evidences for evaluating the ecological risks and toxicity of ILs to marine ecosystem, but also help for understanding their toxic mechanisms to marine diatoms.

Feasibility of Growing Chlorella sorokiniana on Cooking Cocoon Wastewater for Biomass Production and Nutrient Removal.

The feasibility of microalgae cultivation using cooking cocoon wastewater (CCW) collected from a silk production factory was investigated in this work. Results showed that Chlorella sorokiniana grew well on the CCW whether it was autoclaved or not. After 7-day cultivation, the biomass increased by 1.57, 2.78, 3.33, and 3.14 times, and by 3.65, 4.03, 3.27, and 2.82 times when this alga was cultivated in the raw CCW (R-CCW) and autoclaved CCW (A-CCW) at the initial dry cell densities of 0.01, 0.04, 0.08, and 0.16 g/L, respectively. The algal photosynthetic growth was not affected when this alga grew on the R-CCW at an initial dry cell density of ≥ 0.04 g/L, while it was significantly inhibited when the initial dry cell density was 0.01 g/L. Additionally, this alga could remove nutrients rapidly from the CCW, and the removal efficiency increased with the increase of initial dry cell density. Thus, it was concluded that the CCW could be used as a good-quality medium for the algal growth, which is worthy of further study and promotion.

Effects of Water Quality and Post-Harvest Handling on Microbiological Contamination of Lettuce at Urban and Peri-Urban Locations of Ouagadougou, Burkina Faso.

Vegetable production in urban gardens of Ouagadougou contributes to food security, but water for irrigation is often of low quality. This is particularly acute if irrigation water is taken from wastewater polluted channels. This study aimed at (i) verifying to what degree irrigation water quality is correlated with contamination of lettuce with Escherichia coli, total coliforms, and Salmonella spp., and (ii) assessing effects of post-harvest handling on pathogen development during the trade chain. We tested pathogen removal efficiency on lettuce by applying post-harvest washing. Irrigation water of production areas in Ouagadougou (n = 10) showed a mean E. coli load of 2.1 × 105 CFU 100 mL-1. In 60% of the cases, irrigation water did not meet the standards of the World Health Organization (WHO) for safe irrigation water, and in 30% of the cases, irrigation water was contaminated with Salmonella spp. Loads of total coliforms on lettuce leaves ranged from 2.9 × 10³ CFU g-1 to 1.3 × 106 CFU g-1, while E. coli averaged 1.1 × 10² CFU g-1. Results on post-harvest handling revealed that microbial loads increased along the trade chain. Overall, half of all lettuce samples (n = 60) were tested positively for Salmonella spp. The experiment showed that appropriate post-harvest handling could prevent the increase of total coliforms.

Performance evaluation of biofil toilet waste digester technologies in Ghana: the efficacy of effluent treatment options.

The study was carried out to assess the efficacy of a standard Biofil toilet digester with regard to its effluent quality and to evaluate the performance of new effluent polishing options being developed by BiofilCom. Influent and effluent were collected from 18 standard Biofil digesters connected to full-flush toilets. Effluent from five pilot installations with improved effluent polishing options were also taken for analyses. Ten other Biofil installations were selected to assess the impact of digester effluent discharge on the surrounding soil. Pollutant concentrations in the Biofil effluent exceeded both Ghana EPA and WHO standards for discharge though pollutant removal efficiencies were high: 84% for biochemical oxygen demand, 86.1% for chemical oxygen demand and 82.4% for total suspended solids. Escherichia coli and total coliform levels were significantly reduced by 63% and 95.6%, respectively, and nutrients were the least removed from effluents. Generally, effluents from the majority of the pilot polishing options met most of the discharge standards. E. coli were present in the soil at all study sites, except one. Biofil digester effluent is discharged subsurface but comparing their effluent quality with standards for discharge into water courses is relevant especially in areas of frequent flooding and high water tables.

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.

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.

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.

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.