Esi Awuah

COMPARATIVE PERFORMANCE STUDIES OF WATER LETTUCE, DUCKWEED, AND ALGAL-BASED STABILIZATION PONDS USING LOW-STRENGTH SEWAGE

A bench-scale continuous-flow wastewater treatment system comprising three parallel lines using duckweed (Spirodela polyrhiza), water lettuce (Pistia stratiotes), and algae (natural colonization) as treatment agents was set up to determine environmental conditions, fecal coliform profiles and general treatment performance. Each line consisted of four ponds connected in series fed by diluted sewage. Influent and effluent parameters measured included environmental conditions, turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate, nitrite, ammonia, total phosphorus, fecal coliforms, mosquito larvae, and sludge accumulations. Environmental conditions and fecal coliforms profiles were determined in the sediments (0.63 m), suspensions (0.35 m), and surfaces (0.1 m) of each pond. Acidic conditions were observed in the pistia ponds, neutral conditions in duckweed ponds, and alkaline conditions in algal ponds. Fecal coliforms log removals of 6, 4, and 3 were observed in algal, duckweed, and pistia ponds, respectively, in the final effluents, with die-off rates per pond of 2.7, 2.0, and 1.6. Sedimentation accounted for over 99% fecal coliform removal in most of the algal and pistia ponds. BOD removal was highest in the duckweed system, followed by pistia and algae at 95%, 93%, and 25%, respectively. COD removals were 65% and 59%, respectively, for duckweed and pistia, while COD increased in algal ponds by 56%. Nitrate removals were 72%, 70%, and 36%, respectively for duckweed, pistia, and algal ponds. Total phosphorus removals were 33% and 9% for pistia and duckweed systems, while an increase of 19% was observed in the algal treatment system. Ammonia removals were 95% in both pistia and duckweed and 93% in algal systems. Removals of total dissolved solids (TDS) were 70% for pistia, 15% for duckweed, and 9% for algae. Mosquito populations of 11,175/m2, 3516/m2, and 96/m2 were counted in pistia, algal, and duckweed ponds, respectively. Low turbidity and low sludge accumulation characterized the macrophyte ponds. Performance in the removal of fecal coliforms in the algal-based treatment system and organic load removal in both macrophytes and algal-based treatment systems met the Ghana Environmental Protection Agency guideline values.

The effect of different percentages of bulking agent (sawdust) on microbial quality of faecal sludge.

The use of raw sludge spread on land as conditioner and fertilizer has been practised over the years in urban agriculture. However, this raw sludge (biosolids) is associated with a potential health risk as a result of the pathogenic microorganisms it contains. The study considered the dewatering of faecal sludge (FS) mixed with sawdust to produce biosolids that can be applied as manure for agricultural use. It assessed the bacterial and helminth egg qualities of the biosolids produced from FS-sawdust mixture. Bench-scale unplanted filter beds were used for dewatering of FS mixed with different percentages of sawdust. The sludge consisted of public toilet sludge and septage in the ratio of 1:3. An analysis of variance of the completely randomized design was undertaken and a P-value below 0.05 was considered statistically significant. The sawdust-FS mixture analysed after complete dewatering showed significant reduction in microbial (bacteria) content (P < 0.05) and helminth eggs, making the biosolids produced safe for farmers and the environment. The bulking agent improved the quality of the biosolids, with greatest pathogen removal observed in the 150% sawdust, whilst the least reduction was recorded in the 0% sawdust (control).

Needs assessment to strengthen capacity in water and sanitation research in Africa: experiences of the African SNOWS consortium.

BackgroundDespite its contribution to global disease burden, diarrhoeal disease is still a relatively neglected area for research funding, especially in low-income country settings. The SNOWS consortium (Scientists Networked for Outcomes from Water and Sanitation) is funded by the Wellcome Trust under an initiative to build the necessary research skills in Africa. This paper focuses on the research training needs of the consortium as identified during the first three years of the project.MethodsWe reviewed the reports of two needs assessments. The first was a detailed needs assessment led by one northern partner, with follow-up visits which included reciprocal representation from the African universities. The second assessment, led by another northern partner, focused primarily on training needs. The reports from both needs assessments were read and stated needs were extracted and summarised.ResultsKey common issues identified in both assessments were supervisory skills, applications for external research funding, research management, and writing for publication in the peer-reviewed scientific literature. The bureaucratisation of university processes and inconsistencies through administration processes also caused problems. The lack of specialist laboratory equipment presented difficulties, particularly of inaccessibility through a lack of skilled staff for operation and maintenance, and of a budget provision for repairs and running costs. The lack of taught PhD modules and of research training methods also caused problems. Institutionally, there were often no mechanisms for identifying funding opportunities. On the other hand, grantees were often unable to understand or comply with the funders’ financial and reporting requirements and were not supported by their institution. Skills in staff recruitment, retention, and performance were poor, as were performance in proposal and paper writing. The requirements for ethical clearance were often not known and governance issues not understood, particularly those required by funders.ConclusionsSNOWS believes that working with African universities to develop networks that support African-led research driven by the local context is an effective approach to develop and retain research skills needed to change policy and practice in water, sanitation, and hygiene in Africa.

Optimising ventilation to control odour in the ventilated improved pit latrine

The rate of ventilation through the vent pipe of a ventilated improved pit latrine is the main technical factor that determines its efficiency in odour control aside the maintenance and cleaning practices of the users. Even though the factors affecting the ventilation rate have been well researched, they have not been previously related in a mathematical model to quantify the relative effect of the various factors on the ventilation rate. The objective of this paper is to develop such a model that could be used to optimise and predict the ventilation rate as a function of relevant design criteria and weather conditions. The ventilation rates produced by various design modifications in an experimental ventilated improved pit latrine were measured under monitored weather conditions. A linear regression model was used to assess the relative effect of the various design modifications and the elements of weather on the ventilation rate. It was found that the diameter of the vent pipe is the most important factor which accounts for 53% of variations in the ventilation rate, followed by the external wind speed, which accounts for 25% of changes in ventilation. The provision of windows in other sides of the superstructure other than the windward side leads to a reduction of 32% in the ventilation rate and accounts for 9% of the variations in the ventilation rate. A regression model developed in this study could be used to optimise and predict the ventilation rate based on a set of design criteria and meteorological data.

The Search for an Efficient Black Fly Trap for Xenomonitoring of Onchocerciasis

Onchocerciasis is a neglected tropical disease that has plagued mankind for decades with pathologies that involve the eyes and the skin. The WHO and the global health community have earmarked the disease for global elimination by 2045. However, as control programmes shift focus from reduction of the burden of the disease to elimination, new tools and strategies may be needed to meet targets. Monitoring Onchocerca volvulus larvae in the black fly vectors is an important tool needed to monitor disease dynamics and certify elimination. For decades, human landing collections have been the sole means of acquiring vectors for monitoring of the disease. This procedure has been plagued with ethical concerns and sometimes the inability to harvest enough black flies needed to carry out effective monitoring. Since the 1960s, the WHO recognized the need to replace human landing collections but relatively few field studies have designed and tested alternative traps. This review article systematically discusses some of the key traps tested, their successes, and their challenges. It is the aim of the review to direct research and development focus to the most successful and promising vector traps which could potentially replace the human landing collections.

A Perspective Analysis of Dams and Water Quality: The Bui Power Project on the Black Volta, Ghana

Large dams play an important role in promoting economic and social development in many countries. However, the construction of such dams can have a detrimental effect on the environment. The aim of this study was to investigate perceptions of drinking water quality among inhabitants of selected communities within the Bui Dam environs. With the help of questionnaires, 100 respondents from communities “near to the dam” were randomly selected and interviewed. Their responses were compared with another 100 respondents selected from “far from the dam” communities. These were augmented with in-depth interviews, focus group discussion, and personal observation. Analysis of the results showed that, there were greater proportions (31%) of the participants who lived in “near communities” within the age category 20–25 compared to 19% of their “far communities” counterparts. There were significantly greater proportions of female respondents in the “near to the dam” (57%) compared to respondents in the “far from the dam” communities (52%). The study further showed that the perception of risk of consuming contaminated drinking water was more common among “far from the dam” communities (odds ratio = 4.57). The perception of the quality of water based on some physical properties was investigated as part of our study. Analysis of the results showed that significantly greater proportion of the “far from the dam” communities (35%) perceived their water had an objectionable smell compared to 7% of inhabitants of their other counterparts (p value = 0.001). The study further showed that significantly greater proportion of the study participants in the far from the communities perceived that their water had colour (65%) and they did not drink water from any other source (63%) apart from their stream. The study demonstrated that generally, inhabitants within the study communities perceived the construction of the Bui Power Project has negatively affected their drinking water quality.

Nutrient and Microbial Reduction Properties in Pervious Composites for Blackwater Treatment

The focus of this experiment was to compare the treatment performance of nutrient and microbial reduction in granite (GR), shredded polyethylene terephthalate (SP) and palm kernel shell (PKS) composites after solid/liquid separation of blackwater. Laboratory tests were conducted on replicated specimens of the GR, SP, and PKS pervious composites and the mechanisms of microbial reductions and nutrient transformation in blackwater treatment investigated after filtration. Six cylindrical specimens measuring 110 mm × 100 mm and made from the GR, SP, and PKS were used to determine the physical and hydrologic properties (density and permeability) of the specimens. Additional six pervious specimens measuring 0.3 m × 0.3 m × 0.05 mm were used for the solid/liquid separation of blackwater. Blackwater was first infiltrated through a layer of coir fibre and net lining and then run through each pervious composite specimen. Nutrient (ammonium, nitrate, nitrite, total nitrogen, and total phosphorus) and microbial (Escherichia coli and coliforms) analyses were conducted on the effluent from the specimens and compared. The GR, SP, and PKS particle sizes were seen to be uniformly graded and similar. The composite specimens did not have significant effects on the nutrient transformations and removal of organic matter but for total phosphorus. However, escherichia coli and other coliforms’s growth were limited in the SP. Hydrophobic interactions between the SP composite and microbial cells of the microbes could have promoted attachment and limited their growth. It was observed that the mean pH in the effluent filtered through the composites was higher than in the influent partly due to the availability of calcium carbonate in the cement. The study suggests that the SP composite is a promising alternative to the GR composite for the reduction of microbial constituents in blackwater vis-a-vis its light-weight compared to the other pervious composites.