Browsing by Author "Njau, Karoli"

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Agro-Waste-Derived Hybrid Biochar Exhibits High-Efficiency Removal of Endocrine-Disrupting Compounds
(Springer International Publishing, 2025-04-11) Kasambala, Hildegard; Rwiza, Mwemezi; Mpumi, Nelson; Mwema, Mwema; Njau, Karoli
Poor waste management of the products and products used in water sources becomes a problem for living organisms’ health. Using biosorbent from agro-waste materials becomes the solution for waste management and wastewater treatment. This study investigated the removal of progesterone from aqueous solutions using a biochar adsorbent derived from mixed banana and mango peels. The biosorbent shows high progesterone removal of 97.8 ± 0.02% at 700℃ preparation temperature at an optimal biosorbent concentration of 0.50 g and pH of 8. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Isotherm analysis revealed that the adsorption data best fitted the Freundlich model (R2 = 0.96), with a maximum adsorption capacity (qmax) of 307 mg g−1, indicating multilayer adsorption with a heterogeneous surface. The Brunauer–Emmett–Teller (BET) surface area was 652 m2g−1 with abundant functional groups verified by Fourier Transform Infrared Spectroscopy (FTIR). The Scanning Electron Microscopy image (SEM) indicated that the biochar is porous, contributing to its effectiveness as an adsorbent. Thermodynamics results indicate that the spontaneous nature of adsorption reveals the process. The findings proved the potential of using agricultural mixed waste-derived biochar containing various chemical and physical characteristics as an effective and sustainable adsorbent to remove endocrine disruptors. This technique addresses environmental concerns about water hormone pollution and promotes sustainable waste management practices, but the gradual decrease in adsorption efficiency highlights the importance of optimizing the biochar's chemical composition and structural reliability to maximize its performance.
Agrochemicals use in horticulture industry in Tanzania and their potential impact to water resources
(International Journal of Biological and Chemical Sciences, 2014-04) Lema, Emmy; Machunda, Revocatus; Njau, Karoli
The objective of this review was to analyze the existing information on the use of agrochemicals (Fertilizers and Pesticides) in the Tanzanian horticulture industry especially the Northern regions and their potential to impacting water resources. Agrochemicals play an important role in horticulture, and have been widely used in Tanzania for crop protection and increasing productivity. Apart from these benefits, agrochemicals have the potential to impair the quality of water resources for different end uses. Majority of communities in Tanzania depend on surface water from rivers and lakes for potable uses such as washing, drinking and domestic animals also drink from these sources. Reports from studies done in Northern Tanzania have indicated the presence of significant levels of pesticides, phosphates and nitrates in surface and groundwater. It is apparent that most of the horticultural farms in Northern Tanzania are located on gently sloping land adjacent to water bodies. Thus discharges of wastewaters from horticulture farms may affect the quality of water resources through run-off and groundwater through infiltration if proper management of the agrochemicals is not well adhered to. The agrochemicals that have been widely used and identified as potential environmental pollutants from their use as horticultural chemicals are reviewed. The potentially adverse impacts of these agrochemicals to water resources are discussed. The review concludes with a discussion of the directions for further investigation.
Alternative tanning technologies and their suitability in curbing environmental pollution from the leather industry: A comprehensive review.
(Elsevier Ltd., 2020-04-18) China, Cecilia; Maguta, Mihayo; Nyandoro, Stephen; Hilonga, Askwar; Kanth, Swarna; Njau, Karoli
Chrome tanning remains the most favourite technology in the leather industry worldwide due to its ability to produce leather with attributes desirable for high-quality leather such as excellent hydrothermal stability, better dyeing characteristics and softness. Nevertheless, the technology has been censured globally for its severe environmental detriments and adverse effects on human health and other organisms. Developing alternative eco-friendly tanning technologies capable of producing leather of high quality has remained a challenging scientific inquiry. This review article provides an assessment of various eco-friendly tanning attempts geared towards improving or replacing the chrome technology without compromising the quality of the produced leather. The reviewed publications have ascertained that, these attempts have been centred on recycling of spent liquors; chromium exhaustion enhancement and total replacement of chromium salts. The research gaps and levels of key environmental pollutants from the reviewed technologies are presented, and the qualities of the leather produced from these technologies are highlighted. Of all the examined alternative technologies, total replacement of chromium salts sounds ideal to elude adverse effects associated with chrome tanning. Combination tanning, which implies blending two tanning agents that individually cannot impart desired properties to the leather, is anticipated to be an alternative technology to chrome tanning. Apart from being an eco-friendly technology, combination tanning produces leather with similar features to those produced by chrome tanning. In this regard, blending vegetable tannins with aluminium sulphate provides a promising chrome-free tanning technology. However, further studies to optimize combination tanning technologies to suit industrial applications are highly recommended.
Anaerobic digestion of banana winery effluent for biogas production
(International Journal of Environmental Protection and Policy, 2014-09-30) Bakili, Sophia; Gessesse, Amare; Mtei, Kelvin; Njau, Karoli
he efficiency of banana winery effluent (BWE) in biogas production through improving fermentation process was investigated in this study. The study was conducted in a batch system under mesophilic temperature of 35oC achieved by using controlled thermostat waterbath. Two sets of experiments (labeled as experiment 1 and experiment 2) with five reactors each, were performed in the laboratory. For experiment 1, reactor A was treated as a control with no addition of urea while 1g,2g,3g and 4g of urea were added in reactors B,C,D and E respectively. For experiment 2, different amount of sucrose, that is 0.18g, 0.27g, 0.36g and 0.44g were added in the reactors B, C, D and E correspondingly, and reactor A without sucrose addition was used as the control .Results for experiment 1 revealed that reactor A produced largest volume of biogas (1.93L) followed by reactor B with least amount of urea where 1.37L of biogas was generated. Other reactors produced smaller volume of biogas during the study period. For experiment 2 results indicated large volume of biogas (2.72L) was produced in reactor C with 0.27g of sucrose followed by reactor D (2.71L) with 0.36g sucrose. The biogas produced contained 68.9% - 74.6% methane (CH4). This study concluded that addition of nitrogen source does not increase biogas production from Banana winery effluent while addition of carbon source is important as a source of energy for enhancing C: N ratio for process stability and biogas production.
Anaerobic treatment of tannery wastewater using ASBR for methane recovery and greenhouse gas emission mitigation
(Elsevier, 2017-10) Mekonnen, Anduale; Letaa, Seyoum; Njau, Karoli
The objective of this study was to develop and optimize a pilot scale Anaerobic Sequencing Batch Reactor (ASBR) for the treatment tannery wastewater and reduction of greenhouse gas emission. The performance of the pilot scale ASBR was evaluated at the OLRs of 1.03, 1.23, 1.52 and 2.21 kg m−3 d−1 under mesophilic condition (31 °C). The removal efficiencies of COD and methane yield in the pilot scale ASBR were in the range of 69–85% and 0.17 ± 0.2–0.30 ± 0.02m3/kg COD removed, respectively. The optimum COD removal and methane yield were obtained at OLR of 1.03 kg m−3 d−1 (HRT of 4 days) in the stepwise feeding mode. The maximum amount of COD (83.3 ± 3.6%) converted to methane was also obtained in the same loading rate. At this OLR, the volumetric methane production would be 148,190 m3 per year when the digester will be operated at full scale level. The total amount of GHG emission reduction from factory is estimated in the range between 1500 and 3032 tons CO2-eq per year. Generally, the results of this study showed that ASBR is efficient on generating biogas and reducing greenhouse gas emission while treating high strength wastewater such as tannery. Hence, a full scale ASBR should be developed and used to treat the wastewater generated in the tanning industries.
Analysis of Different Techniques for Improving Performance of Flat Plate Solar Collectors for Fruits Drying
(Tanzania Journal of Engineering and Technology (TJET), 2014-06) Bakari, Ramadhani; Minja, Rwaichi; Njau, Karoli
Fruits drying had become a broader technology in fruits and vegetables value addition. The technology is reported to be a promising way of dying without incurring higher cost but its adaptation has not been feasible in rural areas. Solar dryers have been developed but its poor performance limits its applicability. In this study, several techniques for modifications of traditional solar collector were addressed. It was observed that, varying collector designs in different techniques, a range of collector performances can be employing double duct counter flow, compared to conventional collectors. Likewise performance difference between conventional collectors and studied models were found to be 8%, 7.2%, 6.1% and 5.2% for model parked with charcoal 5 mm wire mesh, 4mm glass thickness and 8 baffles respectively. This study shows that, double duct counter flow system is the best option for improving the performance of the collectors, followed by charcoal and wire mesh. On the hand, using 4 mm glass thickness gave improved performance, however, it is recommended for collector size not exceeding 2 m in length.
Antibiotic-resistant microbial populations in urban receiving waters and wastewaters from Tanzania
(Elsevier, 2023) Ripanda, Asha; Rwiza, Mwemezi; Nyanza, Elias; Miraji, Hossein; Bih, Numfor; Mzula, Alexanda; Mwega, Elisa; Njau, Karoli; Vuai, Said; Machunda, Revocatus
Antimicrobial resistance against certain medications in the pathogenic microbial community is globally increasing due to the continual discharge and disposal of pharmaceuticals in the environment. The phenomenon resulted in significant antibiotic resistance among several exposed Enterobacteriaceae species, with wastewater treatment plants (WWTPs) and rivers serving as significant reservoirs. Despite antibiotic resistance being a tragedy, particularly in treating diseases by using antibiotics, local and regional studies indicating the severity, resistant species and the molecular level insight into these pathogens are scarce, thus requiring immediate intervention. This study, therefore, investigated wastewater from wastewater treatment ponds and receiving waters for the presence of resistant pathogens through phenotypical and molecular approach screening of their genes. Among the 57 analyzed samples, 18 (67%, n = 27) isolates of Klebsiella spp.., 4 (80%, n = 5) isolates of Proteus spp., 1 (100%, n = 1) of isolated Pseudomonas aeruginosa and 6 (18%, n = 34) of E. coli found were resistant to at least 1 among the tested antibiotics. E. coli had an 83% higher proportion of multi-drug resistance (MDR) than Klebsiella spp.., which had 68.5%, and no MDR was shown by P. aeruginosa isolates. Among the 20 bacterial isolates of antibiotic-resistant genes, showed that E. coli harboured 39%, followed by 22% of Klebsiella spp. Eleven (11) isolates of these 20 (55%) contained sulphonamides resistant genes: Sul 1 (n = 4) and Sul 2 (n = 7). Ten (10) isolates (50%) contained the tetracycline-resistant genes in which 4 isolates showed the Tet A, Tet B – 1 and 5 isolates contained Tet D. β-lactamases (bla CTX-M and bla SHV) were found in 7 isolates (35%). The existence of these antibiotic-resistant species in the urban receiving and wastewater presents a threat of transmission of diseases to humans and animals that are not cured by the existing medications, jeopardizing public health safety.
The application of nutrient budget models to determine the ecosystem health of the Wami Estuary, Tanzania
(Elsevier, 2018-04) Kiwango, Halima; Njau, Karoli; Wolanskic, Eric
Using the LOICZ and the UEE models we estimated the nutrient budget in the Wami River estuary, Tanzania, to better understand the functioning of the ecosystem and assess its health. We found that during the wet season, when river flows are high, the residence time of the estuary is typically one day or less, and thus little of the riverine nutrients are processed in the estuary. During the dry season the residence time is much longer and as a result the nutrients are processed in the system. The nutrient budget reveals the importance of other sources of nutrients than just dissolved riverine nutrients; these include riverine detritus inflow, mangrove litter fall, and nutrients from hippo excretion. We found no sign of eutrophication. The estuarine food web thus appears healthy in the saline region of the estuary. However, excessive water abstraction in the catchment has resulted in severely decreased flows in the Wami River in the dry season, to the point that the freshwater part of the estuary has essentially disappeared, i.e. the estuary is now saline up to the tidal limit during the dry season. Though the estuary is protected by being included in the Saadani National Park, the system is stressed by dry season salinization, which is seriously affecting the freshwater-dependent flora and fauna. This calls for remedial ecohydrology-based measures at both the watershed scale and the local scale.
Application of sustainability indicators for the evaluation and selection of robust organic-rich wastewater treatment technology for resource recovery
(AIMS Press, 2024-10-29) Chrisogoni, Paschal; Rwiza, Mwemezi; Njau, Karoli
A comparative study was conducted to compare the performance of waste stabilization ponds (WSPs) with an upflow operation type advanced facultative pond integrated with constructed wetland (AFP-CW) technologies. Our aim was to address gaps in economic, environmental, and social aspects identified in traditional WSPs. Economic, environmental, and social sustainability indicators were used in a mathematical model to select a sustainable technology for organic-rich wastewater treatment for resource recovery. The results showed that for the AFP-CW, economic, environmental, and social indicators were weighted at 10.18%, 51.11%, and 38.71%, respectively, while for WSPs, the percentages were 14.55, 48.39, and 37.06, respectively. The composite sustainability indicator (CSI) for AFP-CW was 42.14% and for WSPs was 39.27%, with the global sustainability indicator (GSi) reaching 21.54% for AFP-CW and 18.88% for WSPs. A sensitivity analysis revealed that the maximum global sustainability indicator was 22.34% for AFP-CW and 19.54% for WSPs. Overall, the AFP-CW was considered a more sustainable technology for wastewater treatment, with lower economic but higher environmental and social sustainability indicators compared to WSPs, which showed higher economic but lower environmental and social sustainability indicators. The sustainability of AFP-CW is supported by its small construction area, nutrient recovery in sludge, biogas recovery, reduced global warming impact, as well as nutrient and water recycling for irrigation.
Application of up-flow anaerobic sludge blanket reactor integrated with constructed wetland for treatment of banana winery effluent
(IWA Publishing, 2017-08-01) Paschal, Charles; Njau, Karoli; Gastory, L; Katima, J
Agroprocessing constitutes sizeable industries in the Eastern Africa region discharging wastes into the environment. Proper management of industrial waste is perceived as expensive and enforcement of laws is weak. Generally, there is low awareness of environmental and socio-economic consequences of polluting the environment. The Banana Investment Limited (BIL) in Arusha Tanzania which produces banana wine from ripe bananas was discharging untreated wastewater into the environment. This project aimed at treating the BIL wastewater to meet environmental standards and recover nutrients, water and energy. The feeding wastewater to the up-flow anaerobic sludge blanket (UASB) with flow rate of 62.4 m3/d had concentrations (mg/L) of chemical oxygen demand (COD) (4,959.3 ± 388.7), BOD5 (1,453.7 ± 110.3), total suspended solids (TSS) (2,431.0 ± 190.5), NH4+ (7.2 ± 1.1), NO3− (23.4 ± 3.2), PO43− (5.12 ± 0.73), volatile fatty acid (0.60 ± 0.09), and Alkalinity (60.00 ± 8.98). After 17 months of operation the system achieved removal efficiencies (%) of COD (99.0), BOD5 (98.6), TSS (96.0), NO3− (88.7), PO43− (50.8). There was a net generation of NH4+ (387.8%) in the system. The biogas produced in the UASB is collected at a rate of 163 m3/d and is used in the boiler at BIL. The dried sludge and the treated water are used for irrigation. The study concluded that integrating the bio-digestion process with polishing stage for water, nutrient and energy recovery ensures compliance to environmental law and provides incentive to treat wastewater while also mitigating greenhouse gases.
Approaches to the mitigation of ammonia inhibition during anaerobic digestion – a review
(IWA Publishing, 2020-06-03) Mutegoa, Eric; Hilonga, Askwar; Njau, Karoli
The digestion process of organic waste rich in high ammonia content has always been a gridlock during methanogenesis process. The free ammonia may increase inhibition/toxicity, which in turn affects the microbial community in the digester and eventually leading to process failures. Substantial methods have been proposed and assessed for curtailing ammonia emissions in anaerobic digesters to attain a safe and steady process so that along with high methane production, high quality of effluents can also be recovered. There are several means for lowering the erratic ammonia in organic wastes which has been in use currently such as the decrease of pH, which favour the formation of ammonium over ammonia in the equilibrium. For example, the use of chemical additives that attach ammonium-N. Ammonia can also be removed from nitrogen-rich substrates during anaerobic digestion through other methods such as struvite precipitation, membrane distillation, air stripping, ion exchange, and adsorption. A thoroughly survey from different articles has shown that ion exchange, adsorption and changing of the C/N ratio through co-digestion technique, are the most commonly studied methods for mitigating ammonia inhibition in wastewater during anaerobic digestion. A detailed review of these methods in the context of nitrogen-rich substrates will be discussed in this paper.
Assessing the Impacts of Land Use and Climate Changes on River Discharge towards Lake Victoria
(MDPI, 2023-05-08) James, Renatus; Amasi, Aloyce; Wynants, Maarten; Nobert, Joel; Mtei, Kelvin; Njau, Karoli
The Lake Victoria basin’s expanding population is heavily reliant on rainfall and river flow to meet their water needs, making them extremely vulnerable to changes in climate and land use. To develop adaptation and mitigation strategies to climate changes it is urgently necessary to evaluate the impacts of climate change on the quantity of water in the rivers that drain into Lake Victoria. In this study, the semi-distributed hydrological SWAT model was used to evaluate the impact of current land use and climate changes for the period of 1990–2019 and assess the probable future impacts of climate changes in the near future (2030–2060) on the Simiyu river discharge draining into Lake Victoria, Northern Tanzania. The General Circulation Model under RCPs 4.5, 6.0 and 8.5 predicted an increase in the annual average temperature of 1.4 ◦C in 2030 to 2 ◦C in 2060 and an average of 7.8% reduction in rainfall in the catchment. The simulated river discharge from the hydrological model under RCPs 4.5, 6.0 and 8.5 revealed a decreasing trend in annual average discharge by 1.6 m3/s from 5.66 m3/s in 2019 to 4.0 m3/s in 2060. The increase in evapotranspiration caused by the temperature increase is primarily responsible for the decrease in river discharge. The model also forecasts an increase in extreme discharge events, from a range between 32.1 and 232.8 m3/s in 1990–2019 to a range between 10.9 and 451.3 m3/s in the 2030–2060 period. The present combined impacts of climate and land use changes showed higher effects on peak discharge at different return periods (Q5 to Q100) with values of 213.7 m3/s (Q5), 310.2 m3/s (Q25) and 400.4 m3/s (Q100) compared to the contributions of climate-change-only scenario with peak discharges of 212.1 m3/s (Q5), 300.2 m3/s (Q25) and 390.2 m3/s (Q100), and land use change only with peak discharges of 295.5 m3/s (Q5), 207.1 m3/s Q25) and 367.3 m3/s (Q100). However, the contribution ratio of climate change was larger than for land use change. The SWAT model proved to be a useful tool for forecasting river discharge in complex semi-arid catchments draining towards Lake Victoria. These findings highlight the need for catchment-wide water management plans in the Lake Victoria Basin.
Assessing the Performance of Constructed Wetland for Acid Mine Drainage Treatment Using Sugarcane Molasses as a Carbon Source
(Scientific Research Publishing, 2025-04-22) Buddy, Zainabu; Njau, Oscar; Rugaika, Anita; Njau, Karoli
Acid mine drainage (AMD) is a widespread environmental issue at mining sites globally. AMD is caused by pyrite oxidation which produces an acidic discharge > 2500 mg/L of sulfate, dissolved heavy metals at high amounts and low pH (2 - 4.5). AMD has serious health impact on living organisms. The present study aimed to assess the performance of locally available, high-organic matter containing by-products, specifically sugarcane molasses (SCM), as a carbon source for AMD treatment. In batch experiments containing SCM and control, 99% sulfate and nitrate reductions were reached. Heavy metal removal efficiencies > 94% were achieved for Cu, Fe, Mn, and Zn, in the SCM inoculated columns, while efficiencies > 42% were recorded in the control columns. The column experiments removed 99% of the initial Al concentrations but were not very effective in COD reduction to acceptable limits. The findings reported by this study verify that high carbon containing substrates can be used to remediate metal and sulfate contaminated water in mining areas.
Assessment of agrochemical residues in wastewater from selected horticultural farms in Arusha, Tanzania
(International Journal of Environmental Sciences, 2015-09-07) Emmy, Lema; Machunda, Revocatus; Njau, Karoli
Arusha region in Tanzania has been involved for quite some time on commercial horticulture. The use of agrochemicals results to increased crop productivity and consequently offers farmers major economic returns. However, the use of agrochemicals and the adjacency of horticultural farms to streams and rivers have the potential to contribute to water pollution if control measures are not effective. We analysed the physical and chemical parameters of wastewater discharged from selected horticultural farms in Arusha and detected nitrates (NO3-), phosphates (PO43-), sulphates (SO42-) and permethrins insecticide in the effluents discharged into the environment. The mean concentration levels ranged from (4.5 ppm - 64.08 ppm) for NO3-, (3.22 ppm - 47.64 ppm) for PO43-, (91.42 ppm - 139 ppm) for SO42- and permethrin was 0.63 ppm. Of all the farms monitored, eighty percent (80%) had high levels of PO43-, sixty percent (60 %) had high levels of NO3- and twenty percent (20 %) had high levels of permethrin above the allowable limits for discharge into receiving water resources. It may be concluded that the continued agrochemical use may lead to contamination of adjacent water resources which may in the long run cause adverse health effects to the downstream water users. Continual monitoring of agrochemical residues is recommended to inform and ensure compliance with the stipulated standards and regulations for wastewater discharg
Assessment of dairy wastewater treatment and its potential for biogas production at Tanga fresh limited
(Tanzania Journal of Science, 2016-03-16) Nyaki, Anna; Njau, Karoli
The extent of pollution of dairy wastewater treated in a septic tank and its potential for biogas production was investigated. Performance of the existing treatment system was assessed through characterization of both raw and treated effluents. From the analysis parameters likeChemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), Total Suspended Solids (TSS), alkalinity, turbidity, color and phosphorus disclosed inadequate system performance with treated effluent displaying higher values of organic matter than the allowed discharge limits according to the national standards. Optimal conditions for biogas production such as temperature, pH and type of inoculum were determined through batch experiments. The optimum conditions were 35 oC and pH 7.0 with cow dung as inoculum type, which resulted in production of 0.49 m3 of biogas per Kg COD of dairy wastewater. The reduction efficiencies of COD, TS and VS were 98%, 78% and 73%, respectively. Therefore, these conditions can be applied for treatment of wastewater at Tanga fresh limited (TFL) Plant, to ensuring adequate dairy wastewater treatment and recovery of biogas while preventing environmental pollution from the 100 m3 of dairy wastewater produced daily.
Assessment of fluoride removal in a batch electrocoagulation process: A case study in the Mount Meru Enclave
(Elsevier B.V., 2021-03-04) Mureth, Risala; Machunda, Revocatus; Njau, Karoli; Dodoo-Arhin, David
The presence of excessive amounts of fluoride than prescribed standards has been reported in various sources of domestic water supply around the slopes of Mount Meru and other parts in Tanzania. Efforts to remove the excessive fluoride have been carried out using various technologies. In this study, electrocoagulation experiments were carried out to assess its efficiency on fluoride removal. The fluoride concentration tested ranged from 1.37 to 48 mg/L in both synthetic and natural waters. The voltage applied in the electrocoagulation (EC) process ranged from 0 to 50 V while maintaining pH values of 4 to 9. The representative experimental results for the Ngarenanyuki river water with initial fluoride concentration of 29.5 mg/L accomplished a removal efficiency of 90% at an optimal electrolysis time of 30 min, an applied voltage of 30 V and an optimal pH of 6. The method showed efficient fluoride removal in water to allowable limits by World Health Organization (WHO) and Tanzania Bureau of Standards (TBS) (1.5 mg/L). Despite the voltage applied (30 V), the pH at neutrality remained unchanged thus making the process more efficient. At this voltage (30 V) the process has been reported previously also to have the capability of disinfecting the water and hence rendering such water safe for use
Assessment of fluoride removal in a batch electrocoagulation process: A case study in the Mount Meru Enclave.
(Elseiver, 2021-03-01) Mureth, Risala; Machunda, Revocatus; Njau, Karoli; Arhin, David
The presence of excessive amounts of fluoride than prescribed standards has been reported in various sources of domestic water supply around the slopes of Mount Meru and other parts in Tanzania. Efforts to remove the excessive fluoride have been carried out using various technologies. In this study, electrocoagulation experiments were carried out to as- sess its efficiency on fluoride removal. The fluoride concentration tested ranged from 1.37 to 48 mg/L in both synthetic and natural waters. The voltage applied in the electrocoag- ulation (EC) process ranged from 0 to 50 V while maintaining pH values of 4 to 9. The representative experimental results for the Ngarenanyuki river water with initial fluoride concentration of 29.5 mg/L accomplished a removal efficiency of 90% at an optimal elec- trolysis time of 30 min, an applied voltage of 30 V and an optimal pH of 6. The method showed efficient fluoride removal in water to allowable limits by World Health Organiza- tion (WHO) and Tanzania Bureau of Standards (TBS) (1.5 mg/L). Despite the voltage applied (30 V), the pH at neutrality remained unchanged thus making the process more efficient. At this voltage (30 V) the process has been reported previously also to have the capability of disinfecting the water and hence rendering such water safe for use.
Assessment of water quality variation in rivers through comparative index technique and its reliability for decision making
(Tanzania Journal of Science, 2018) Kitalika, Aldo; Machunda, Revocatus; Komakech, Hans; Njau, Karoli
The National Sanitation Foundation (NSF) and Weighed Arithmetic Index (WAI) methods for water quality index (WQI) have been studied to evaluate their reliability in water quality assessment in rivers. Water samples were collected in various GPS predetermined points in Temi, Nduruma, Tengeru and Maji ya Chai rivers-Tanzania during wet and dry seasons and were analyzed for several water quality parameters using standard methods as per APHA. Medium to excellent water qualities were observed for pristine environment in three rivers except Maji ya Chai under NSF and WIA methods, respectively. Excellent water quality was observed in the pristine environment of Temi and Tengeru rivers during wet season. Maji ya Chai water was identified unsuitable for drinking throughout the year. Fecal Coliforms (FC), Nutrients content, BOD and Fluorides (F- ) were the major contributors to the poor water quality in Maji ya Chai whereas FC and Nutrients were a serious problem in flood-plain for other rivers. The two methods showed different overall Water Quality Indices using the same data thus, making them unreliable tools for water quality assessment when used simultaneously for the same purpose. Therefore selection of the method for water quality assessment and decision making may depend on the water use.
Avoiding the Use of Exhausted DrinkingWater Filters: A Filter-Clock Based on Rusting Iron
(MDPI, 2018-05-02) Ndé-Tchoupé, Arnaud Igor; Lufingo, Mesia; Hu, Rui; Gwenzi, Willis; Ntwampe, Seteno Karabo Obed; Noubactep, Chicgoua; Njau, Karoli
Efficient but affordable water treatment technologies are currently sought to solve the prevalent shortage of safe drinking water. Adsorption-based technologies are in the front-line of these efforts. Upon proper design, universally applied materials (e.g., activated carbons, bone chars, metal oxides) are able to quantitatively remove inorganic and organic pollutants as well as pathogens from water. Each water filter has a defined removal capacity and must be replaced when this capacity is exhausted. Operational experience has shown that it may be difficult to convince some low-skilled users to buy new filters after a predicted service life. This communication describes the quest to develop a filter-clock to encourage all users to change their filters after the designed service life. A brief discussion on such a filter-clock based on rusting of metallic iron (Fe0) is presented. Integrating such filter-clocks in the design of water filters is regarded as essential for safeguarding public health.
Bacterial communities structure in constructed wetlands for municipal and industrial wastewater treatment in Tanzania
(IWA Publishing, 2023) Msaki, Gerubin; Kaale, Sadikiel; Njau, Karoli; Lyimo, Thomas
Bacteria are the largest and most essential microorganisms in wastewater treatment systems. Despite the vital role bacteria play in enhancing wastewater treatment, its community structure and diversity remain poorly known. This study elucidated bac- terial diversity and community structure in constructed wetlands (CWs) for municipal and industrial wastewater treatment using a culture-independent approach. Analysis of physicochemical parameters and Illumina high-throughput sequencing of V3 and V4 hypervariable regions of 16S rRNA gene bacterial community was performed. The results showed that the Proteobacteria were dominant (48.66%) phyla across all CWs. The Gammaproteobacteria class (27.67%), family Comamonadaceae (35.79) and Genus Flavobacterium (4.35%) were dominant across studied CWs. Bacterial abundance increased from the inlet to the outlet, with CWs having a higher abundance around the outlet, showing a good performance. The Shannon–Wiener index showed the highest species diversity (H ¼ 1.45) in Banana Investment Limited CWs treating industrial wastewater. This study found significant bacterial diversity across studied CWs, with higher abundance and diversity at the outlet indicating better per- formance than those with low abundance and diversity at the outlet. We recommend a longitudinal investigation at each CWs section to confirm and establish the role of bacterial diversity on the performance pattern of CWs.