Optimization of Biogas Production Process in Solid State Digesters in Semiarid Areas of Northern Tanzania

Solid state digestion process has received much attention due to its low water requirements, making it preferred in semi-arid areas as well. In this study, the performance of the household solid state digesters was evaluated through monitoring of the feedstock mixing ratios and using the digester gas pressure as a measure of performance. Additionally, a batch study to verify the appropriate and optimal mixing ratio of feedstocks was also done. The mixing ratios of cow dung to water ranged from 2:1, 3:1 and 4:1. Total solids determined were 120, 150 and 170 mg/g for the ratios 2:1, 3:1 and 4:1, respectively. Biogas yield for 2:1, 3:1 and 4:1 mixing ratios in laboratory batch mode were 21.4, 22.7 and 46.4 mL/gVS, respectively. These results from a practical scenario show a promising future of the technology which can be adopted by all solid state digester users living in dry areas. Key words: Cowdung, Biogas, Mixing ratio, Batch solid state anaerobic digeste

In-situ synthesis of calcium/magnesium phosphate system for water de-fluoridation: Clay ceramic materials

This research article was published, Elsevier, Volume 278Clay ceramic water filters impregnated with silver colloids have been used to purify water in many parts of East Africa disregarding the removal of fluoride, which is a health-threatening ion in water supplies. This paper presents a synthesis of clay ceramic materials containing in-situ generated calcium/magnesium phosphate system as an adsorbent for water de-fluoridation. The materials were prepared in varied ratios of clay (K) to heat-pretreated dolostone (R) (K:R = 0:100, 90∶10, 85∶15, 75∶25 and 100:0), sintered at temperatures between 500 °C and 900 °C, and characterized using XRF, AAS, CHNS–O analyzer and X-ray PDF analysis. The materials improved in de-fluoridation performance with increase in sintering temperature at 500–700 °C, before exhibiting a sharp drop at 800 °C. The adsorption performance of K:R = 75:25 was higher than that of K:R = 0:100, signifying the effect of clay. The adsorption data obeyed Freundlich isotherm model, suggesting multi-layer adsorption. Fluoride uptake follows pseudo-second-order and intra-particle diffusion models, which suggests a chemisorption process involving rate-limiting intra-particle diffusion

Effect of Elevated Temperature on Compressive Strength and Physical Properties of Neem Seed Husk Ash Concrete.

This research article published by MDPI, 2020High temperature rise mostly caused by a fire outbreak is currently becoming a threat that endangers concrete's structural performance for buildings and the safety of occupants. The behavior of concrete after fire subjection has been of much interest for the structural materials design purposes. This study investigated the physical properties and the compressive strength of M25 concrete incorporating Neem Seed Husk Ash (NSHA), exposed to and through targeted different levels of temperature (200 °C to 800 °C) for a period of three hours in an electric furnace. The NSHA was produced by calcining neem seed husks at 800 °C for six hours and then sieved through the 125 μm sieve. Different amounts of NSHA were investigated while considering the plain concrete as the control sample. 150 concrete cubes of 150 mm sizes were cast and properly cured for 7 and 28 days. The experimental results show that the compressive strength of the 5% NSHA concrete exposed to temperatures up to 400 °C is 21.3% and 23.8% better than the normal concrete at 7 and 28 curing days, respectively. Surface cracks and spalling are noticeable at 600 °C and 800 °C for all samples considered in this study

Performance of water filters towards the removal of selected pollutants in Arusha, Tanzania.

This paper presents the findings of a study carried out to investigate the efficiency of selected common water filters in the removal of Escherichiacoli, organic matter and fluoride. Additionally, the Total Suspended Solids, Turbidity andcolour were also considered for assessing the performance of the filters in ensuring safe water provision. The results showedthat various filters performed differently at particular retention times. Removal of Escherichia coli, was found to be 100%, 75%, 96%, 96.5, 98.5%forbio-sand, slow sand, ceramic, bone char and membrane purifier respectively. Organic matter removal was found to be 47%, 43%, 53%, 43.4% for bio-sand, slow sand, ceramic and membrane purifier respectively, while, fluoride removal was found to be 95.5% for bone char filter. Furthermore, filters were also assessed in terms of media availability, buying costs, operation, benefits/ effectiveness towards major pollutants, and drawbacks. The study concluded that filters currently present in the market especially in Arusha are effective towards specific pollutants. To remove multiple pollutants, an integrated filter would be needed for optimized performance.Key words: water filters, water purification, E. coli, organic matter, fluorid

Recovery of acetyl cholinesterase inhibition by Methanolic Bark Extract of Acacia nilotica from Organophosphate Pesticides Exposure in mice model

This research article published by International Journal of Biosciences, Vol. 16, No. 1, 2020Organophosphates (OPs) pesticides are reported to cause acute poisoning because of their ability to inhibit acetyl cholinesterase enzyme (AChE). Available antidotes drugs are atropine sulfur, Pralidoxime (2-pyridine aldoxime methyl chloride) and diazepam, which act to recover OP-AChE inhibition. These are controlled drugs not easily accessed and very expensive. In this present study Acacia nilotica was assessed for its antioxidant activity, and in vivo AChE depression and recovery from OP-AChE inhibition. The mice were exposed in three different OPs including chlorpyrifos 480g/l (CPF), Fenitrothion 10g/l (FNT) and Profenophos 720g/l (PFP). The methanolic bark extract of A. nilotica had a substantial increase of absorbance readings from 2.895±0.0032 to 3.716±0.0259 compared to standard (ascorbic acid) from 0.108±0.0033 to 1.468±0.0297 at P<0.05. AChE depression and recovery were assessed by using the AChE test mate kit to analyze blood collected from the mice’s tail. Recovery effect under crude methanolic extract from A. nilotica, ascorbic acid and normal feeding were compared with the untreated group. Results have shown that there is a significant decrease of AChE level from Day zero to 14th day in all treated groups of CPF, PFP and FNT which indicate poisoning. Significance of AChE recovery observed only in male mice in all treatment groups. This is a first study to assess and report the antioxidant activity of stem bark methanolic extracts of A. nilotica in controlling organophosphate pesticide toxicity in mice, hence further studies on isolation of active compounds are recommended

Photocatalytic degradation of azo dyes in textile wastewater by Polyaniline composite catalyst-a review

This research article was published by Elsevier B.V in 2022Azo dyes in industrial textile and dye effluent (5–30%) have become irresistibly recalcitrant and toxic to both treatments and the environment respectively. Global concerns about the persistent nature of these dyes and the limitation of the conventional treatment currently in place have led to this critical analysis and evaluation of the photocatalytic approach using nano-technology. The review of literature has indicated that although this approach is effective, however, the limitation of frequent electron-hole recombination during the process coupled with challenges of agglomeration of nano particle powder, photo-corrosion and photosensitivity of the various nano-materials are still challenges associated with the development of polymeric based nano composite catalyst of polyaniline (PANI). The unique features of incredible charge transport properties, surface morphology and enhanced functional properties gave PANI the choice of use among other conductive polymers for composite fabrication with materials such. Photoactive properties, conductivity mechanical, thermal and chemical stability equally offers the polymer the propensity of bandgap tunability when in composites with other materials. Consequently, effective recovery and reuse of the composite catalyst for more than four runs with efficiency > 90% becomes obtainable. These appreciable advantages offer fabricated nano composite polymeric-based catalysts an effective outlook of use in the remediation of toxic azo dyes industrially as compared to the bio-catalyst and pure nano adsorbent materials. Therefore, the review discusses the treatment process for azo dyes, fabrication and performance evaluation of improved composite catalyst of PANI as an alternative to the conventional catalyst in wastewater and recommends for further investigation in PANI to enhance treatability of azo dyes

Cattle dung production, management and utilization practices in the smallholding dairy farming systems of East Africa: A situational analysis in Lushoto District, Tanzania

This research article was published by Journal of Biodiversity and Environmental Sciences in 2018This focus review aims to update the dung and manure production, management and utilization in the East African countries and its associated challenges particularly in the case of Lushoto district, in northern Tanzania. Attention and efforts are continuously being made to promote the use of cattle dung though the challenges still exist. Majority of smallholder farmers in the East Africa poorly manage cattle dung such that its quality is impaired. Such practices include exposing the dung uncovered in a heap and applying directly to the crops. A survey conducted at Lushoto district in the smallholder dairy farmers observed poor management from collection of dung, processing or storage to utilization causing losses of potential nutrients when it’s used as manure. Additionally, the knowledge on other uses of cow dung such as for biogas production is not adequately known. This review, therefore, revealed the need for training farmers on issues related to dung management and utilization such as the nutrient recycling at the farm scale. Cattle dung has been for a long time used as manure in agricultural production and recommendations especially on the applications and users have been generalized to a wide range of areas. There is a need to establish area specific recommendation on dung management from production to the final use. For sustainability of the knowledge, readable materials, an appropriate intervention of biogas plant, manure storage (shade structure) and decomposition process that will create awareness from production to farm application are required

Assessment of agrochemical residues in wastewater from selected horticultural farms in Arusha, Tanzania

This research articles was published by International Journal of Environmental Sciences in 2015Arusha 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 dischar

Numerical Analysis of Heat Exchanger for Spray-Assisted Low-Temperature Desalination System

This research article was published by Hindawi in 2020A numerical study for heat exchanger for spray-assisted low-temperature desalination system is presented for an existing low-temperature desalination unit at Arusha Technical College. This is aimed at recognizing the effect of mass flow and physical parameters like tube layout (diameter and length) on the overall heat transferred and the pressure drop in the shell-and-tube heat exchanger (STHX), as well as the impact of these parameters on the heat transfer coefficient and the overdesign of the STHX. Also, the study provides a suitable mathematical model for the replacement of the current condensation unit which tends to reduce energy consumption by reducing some of the electrical components in the system. A Math CAD model was developed using the Delaware method to obtain the mentioned parameters. The results show that at 0.8 kg/s flow rate a maximum heat transfer coefficient of 23212 W/m2K is achieved in a minimum diameter of 10 mm within a maximum tube length of 1000 mm heat exchanger and the pressure drop seems to be very low in a range of 0.328-0.957 Pa from all configurations. The configuration with 1000 mm tube length and 10 mm diameter performed well on the mass flow of 0.3 kg/s-0.8 kg/s by providing a suitable overall heat transfer coefficient of 2306-2539 W/m2K, while 12.8 is a maximum overdesign coefficient achieved on 0.8 kg/s mass flow. The study results show the possibility of using STHX instead of the current condensation unit in implementing a proposed system layout with the minimum effect of energy consumption

Impacts of Wood Fuel Uses on Forest Cover: The Case of Semiarid Areas in Northern Tanzania

Satellite images for the years 1987, 1997, 2002 and 2017, and questionnaire surveys were used to assess energy sources and demands as well as the impacts of wood fuel use to forest cover changes in Meru and Mwanga Districts. The major energy sources identified include cow dung cake, firewood, charcoal, liquefied petroleum gas and biogas. The total energy demands from these sources were 1400 (in Meru), 6289, 724 and 21 kg per day, respectively. The amount of biogas was not quantified since the reactors were constructed locally with no reading meter. Analysis from Landsat images showed variations in forest cover. The areas covered with forests in Meru were found to be 1510, 1723, 1612 and 1327 ha for 1987, 1997, 2002 and 2017, respectively. The changes observed in Mwanga District were 31705, 31988, 17939 and 30960 ha for 1987, 1997, 2002 and 2017, respectively. From the findings it was observed that, the ongoing use of wood fuel in semi-arid areas of Meru and Mwanga could deplete forests completely. The study concludes that charcoal and firewood consumptions are real threats to the long-term persistence of forests in Tanzania and proposes the use of renewable energy such as biogas for alleviating forest losses. Keywords: Biogas, energy sources, Satellite image