Efficacy of waste stabilization ponds and constructed wetlands adopted for treating faecal sludge in Africa: a review.

The generation of faecal sludge (FS) in capitals and urban settings of African countries outpaces the available storage, emptying, transportation and treatment technologies. The low technology-based treatment systems for handling FS are preferable and widely adopted in the African context due to their less associated investment and operation costs. The waste stabilization ponds and constructed wetlands were principally developed as wastewater treatment systems however they are widely adopted for treating FS in urban settings of Africa. Less information is known about the efficiency of these systems in lowering FS pollutant concentrations to meet the design specifications and the allowable discharge limits. This paper reviewed the technical efficacy of waste stabilization ponds and the constructed wetlands in treating FS by evaluating the actual treatment efficiency data against the design efficiencies and the maximum allowable discharge limits. The review results revealed that these technologies are user-friendly although they fail to lower the solids concentrations to meet the design and maximum allowable discharge limits. This failure imposes extra costs on operation and maintenance due to the fast filling of solids in the systems hence leading to short-circuiting issues. So, studies on the adequate dewatering technologies of FS before entering the systems are needed.

Evaluating the performance of faecal sludge dewatering technologies in urban settings of developing African countries: a review.

Inadequate dewatering technologies are reported as the dominant challenge in handling faecal sludge (FS) within urban settings of most African countries. Studies have been carried out to evaluate the efficiencies of unplanted sand drying beds (USDBs), decentralized wastewater treatment systems (DEWATS), and geo-tubes. However, limited information is available on comparative capabilities in dewatering the FS. This work reviewed treatment efficiencies by assessing the reported actual waste removal capacities and ascertaining if they align with the design removal provisions. Peer-reviewed papers, books, and technical reports from trusted sources were examined. The results show that all the technologies perform best in dewatering the FS; however, USDBs are widely adopted for city-wide treatment, and the other two are suited for decentralized communities. The USDB is challenged by frequent clogging and poor quality of dewatered sludge when reused or recycled in the production of solid fuel and compost due to sticking sand after sludge harvesting. The DEWATS and geo-tubes increase operational costs when used to treat the FS at a large scale. More studies should be conducted to explore locally made, cost-effective filter media and technologies to enhance the dewatering quality and quantity of the FS and increase the quality of recycled by-products.

This paper reviewed the capabilities of sand drying beds, decentralized wastewater treatment systems (DEWATS) and geo-tubes in dewatering the faecal sludge (FS).All reviewed dewatering technologies significantly reduce the solid concentration of faecal sludge, so they perform best in dewatering the FS.Sand drying beds are considered a suitable technology for city-wide sanitation management, the other two are best suited for decentralized communities.Although sand drying beds are viewed as the most promoted and adopted city-wide dewatering technology, they face clogging and poor quality of harvested dry solids for reuse and recycling purposes.More studies on alternative filter media and/or technologies are urgently needed. If the filter media is in contact and or is removed together with dry sludge during harvesting, then the media should be organic so that it enhances the quality of reused or recycled byproducts.

Data from the batch adsorption of ciprofloxacin and lamivudine from synthetic solution using jamun seed (Syzygium cumini) biochar: Response surface methodology (RSM) optimization.

This dataset expresses the experimental data on the batch adsorption of ciprofloxacin and lamivudine from synthetic solution using jamun seed (JS) (Syzygium cumini) biochar. Independent variables including concentration of pollutants (10-500 ppm), contact time (30-300 min), adsorbent dosage (1-1000 mg), pH (1-14) and adsorbent calcination temperature (250,300, 600 and 750 °C) were studied and optimized using Response Surface Methodology (RSM). Empirical models were developed to predict the maximum removal efficiency of ciprofloxacin and lamivudine, and the results were compared with the experimental data. The removal of polutants was more influenced by concentration, followed by adsorbent dosagage, pH, and contact time and the maximum removal reached 90%.

In situ facile green synthesis of Ag-ZnO nanocomposites using Tetradenia riperia leaf extract and its antimicrobial efficacy on water disinfection.

In this work, Ag-ZnO nanocomposites were prepared by a green synthesis route using aqueous leaf extract of Tetradenia riperia and investigated for antibacterial activity against Escherichia coli and Staphylococcus aureus. To optimize the synthesis of the Ag-ZnO, the effects of precursor concentrations, pH, and temperatures were studied. The Ag-ZnO nanocomposites were characterized by XRD, ATR-FTIR, FESEM, and TEM. Results show that the concentration of 8% Ag, the temperature of 80 °C, and a pH of 7-8 were optimal for the synthesis of Ag-ZnO nanocomposites. The XRD analysis showed the decrease in particle size of Ag-ZnO from 23.6 to 14.8 nm with an increase in Ag concentrations, which was further supported by FESEM analysis. TEM image of 8% Ag provides more information on the coexistence of Ag on ZnO where an average particle size of 14.8 nm was determined. The ATR-FTIR analysis confirmed the presence of phenolic compounds, which work as reducing and stabilizing agents. The antimicrobial activity results show that Ag-ZnO nanocomposite demonstrated a higher antimicrobial potency on E. coli than on S. aureus. Therefore, Tetradenia riperia leaf extract is a viable route for the synthesis of Ag-ZnO nanocomposites to be used for various applications, including water disinfection.

What influences individuals to invest in improved sanitation services and hygiene behaviours in a small town? A formative research study in Babati, Tanzania.

Sub-Sahara African countries face immense challenges in ensuring adequate sanitation and hygiene behaviours to the rapidly growing populations. Attempts to address these challenges require empirical evidence to inform policy and planning. We contribute toward that goal by unveiling findings of formative research conducted in Babati, a rapidly growing town in Tanzania. We conducted a cross-sectional study involving 486 households, to unwind motives and barriers for individuals to invest in improved sanitation services and hygiene behaviour change. We used several methods including household survey, focus group discussions, behaviour observations and spot checks. The findings revealed that households derive their motivation to invest in improved sanitation and hygiene practices from comfort, raising social status, and the need for personal safety and privacy. Other motives include fear of penalties and fines and fear of disease outbreaks, whilst the barriers include, limited water availability and accessibility, environmental factors, property rights, cultural issues, financial constraints, and a person's attitude. Quantitative data were subjected to multivariate analysis to identify determinants of households to invest in sanitation and hygiene practices. The logistic regression analyses revealed that sources of water, property rights, and education level were the main determinants of households to invest in sanitation and hygiene facilities, while household income was the main determinant for households to invest in both construction of handwashing facility and water treatment. We argue that the initiative to promote sanitation and hygiene behaviour change in small towns should focus on promoting motivation factors and abating the determinant factors identified in this study.

Two-stage banana leaves wastes utilization towards mushroom growth and biogas production.

Banana leaves wastes (BL) were subjected to fungal treatment using Pleurotus ostreatus to produce edible mushrooms and biogas in the anaerobic digestion process. Effects of fungal treatment on mushrooms production, lignin degradation, trace elements compositions and biogas yield during the anaerobic digestion process were evaluated. Treatment with P.ostreatus for 36 d resulted in the production of 181 ± 19 g of edible mushrooms per 2 kg of BL with biological efficiency of 37 ± 4%. Lignin concentration in fungal treated BL decreased by 10% indicating an improvement on its digestibility. Important trace elements (Fe, Mn, Mo, Co and Ni) necessary for the improvement of the anaerobic digestion process were also significantly reduced (P < 0.05) during the fungal treatment process. The biogas yield for the fungal treated BL was 282 mL g-1 VS-1 of which this study suggests that could be improved through trace element supplementation during the anaerobic digestion process.

Quantitative assessment of metal contamination and associated pollution risk in sediments from the Mara River in Tanzania.

For most rivers in sub-Saharan Africa, information about pollution indices related to sediments is sparse. Sedimentological research of rivers that empty into Lake Victoria is highly patchy and wide apart. The present study determined the levels and associated risk of As, Cd, Cr, Hg, and Pb in sediments collected from four different sites along the Mara River that empties into Lake Victoria in Tanzania. Samples were collected in the dry and rainy months in 2019. Pollution indices, namely geo-accumulation index (Igeo), enrichment factor (EF), contamination factor (CF), modified contamination degree (mCd), pollution load index (PLI), potential ecological risk factor (Eri), and potential ecological risk index (RI) were used to evaluate the influence of heavy metal contamination in sediments. Dry month mean concentrations, in milligram per kilogram, of heavy metals were as follows: As (11.04 ± 0.13), Cr (1.02 ± 0.29), Cd (0.43 ± 0.05), and Hg (0.01) in the dry month. Respective sediment heavy metal concentrations for the rainy month were 22.22 ± 0.05 mg As/kg, 3.84 ± 0.34 mg Pb/kg, 1.53 ± 0.15 mg Cd/kg, 1.43 mg Cr/kg, and 0.03 mg Hg/kg. Generally, the risk indices showed high values in the rainy month and low values in the dry month, especially for As and Cd-an indication of anthropogenic influence. Correlation coefficient analysis for Pb and Cd showed a strong positive correlation (r = 0.99, p < 0.01)-this may suggest a similar source or similar transport behavior. Special attention needs to be paid with regard to rainy season As and Cd enrichment in the study area.

Sanitation and Hygiene Practices in Small Towns in Tanzania: The Case of Babati District, Manyara Region.

Formative research findings from the fast-growing Babati town were used to assess the prevalence of sanitation and hygiene practices among individuals and institutions and associated factors. A cross-sectional study involving household surveys, spot-checks, focus group discussions, in-depth interviews, and structured observations of behaviors showed that 90% of households have sanitation facilities, but 68% have safely managed sanitation services. The most common types of household sanitation facilities were pit latrines with slab (42%) followed by flush/pour flush toilets (32%). Therefore, the management of wastewater depends entirely on onsite sanitation systems. The majority of households (70%) do not practice proper hygiene behaviors. Thirteen percent of the households had handwashing stations with soap and water, handwashing practice being more common to women (38%) than men (18%). The reported handwashing practices during the four critical moments (handwashing with soap before eating and feeding, after defecation, after cleaning child's bottom, and after touching any dirt/dust) differed from the actual/observed practices. Households connected to the town's piped water supply were more likely to practice handwashing than those not directly connected. Sanitation and hygiene behaviors of the people in the study area were seen to be influenced by sociodemographic, cultural, and economic factors. The conditions of sanitation and hygiene facilities in public places were unsatisfactory. There is an urgent need to ensure that the sanitation and hygiene services and behaviors along the value chain (from waste production/source to disposal/end point) are improved both at the household level and in public places through improved sanitation services and the promotion of effective hygiene behavior change programs integrated into ongoing government programs and planning.

Alternative tanning technologies and their suitability in curbing environmental pollution from the leather industry: A comprehensive review.

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.

Refining Network Lifetime of Wireless Sensor Network Using Energy-Efficient Clustering and DRL-Based Sleep Scheduling.

Over the recent era, Wireless Sensor Network (WSN) has attracted much attention among industrialists and researchers owing to its contribution to numerous applications including military, environmental monitoring and so on. However, reducing the network delay and improving the network lifetime are always big issues in the domain of WSN. To resolve these downsides, we propose an Energy-Efficient Scheduling using the Deep Reinforcement Learning (DRL) (E2S-DRL) algorithm in WSN. E2S-DRL contributes three phases to prolong network lifetime and to reduce network delay that is: the clustering phase, duty-cycling phase and routing phase. E2S-DRL starts with the clustering phase where we reduce the energy consumption incurred during data aggregation. It is achieved through the Zone-based Clustering (ZbC) scheme. In the ZbC scheme, hybrid Particle Swarm Optimization (PSO) and Affinity Propagation (AP) algorithms are utilized. Duty cycling is adopted in the second phase by executing the DRL algorithm, from which, E2S-DRL reduces the energy consumption of individual sensor nodes effectually. The transmission delay is mitigated in the third (routing) phase using Ant Colony Optimization (ACO) and the Firefly Algorithm (FFA). Our work is modeled in Network Simulator 3.26 (NS3). The results are valuable in provisions of upcoming metrics including network lifetime, energy consumption, throughput and delay. From this evaluation, it is proved that our E2S-DRL reduces energy consumption, reduces delays by up to 40% and enhances throughput and network lifetime up to 35% compared to the existing cTDMA, DRA, LDC and iABC methods.

Where does land use matter most? Contrasting land use effects on river quality at different spatial scales.

Understanding the influence of land-use activities on river quality has been a key focus of river monitoring programs worldwide. However, defining which land-use spatial scale is relevant remains elusive. In this study, therefore, we contrasted the influence of land use on river quality using three types of land-use estimators, namely circular buffers around a monitoring site, circular buffers upstream of the monitoring site and the entire watershed area upstream of the monitoring site. The land-use percentage compositions within the Usa-Kikuletwa River catchment in northeastern Tanzania were quantified using Landsat-8 satellite images with a maximum mapping resolution of 30 m. Redundancy analysis models and generalized linear models were used to evaluate the influence of land use on macroinvertebrate assemblages and physico-chemical water quality at different spatial scales in the dry and wet seasons. Overall, a substantial fraction of variation in physico-chemical water quality, macroinvertebrate taxon richness, Chao-1 and TARISS (Tanzania River Scoring System) score could be explained by land use of the entire watershed area upstream of the monitoring site in the dry and wet seasons. However, macroinvertebrate abundances showed strong links with more local land-use patterns within 100 m and 2 km radii. Circular buffers upstream of monitoring sites were more informative for macroinvertebrate assemblages than circular buffers around the monitoring sites. However, the latter did correlate well with physico-chemical water quality variables. Land-use variables correlated across spatial scales (i.e., 100 m up to 2 km radii), but not with the land use in the entire watershed area above the monitoring site. Our results indicate that physico-chemical water quality variables and macroinvertebrates may respond differently to land-uses at different scales. More importantly, our results illustrate that the choice regarding spatial land-use metrics can bias conclusions of environmental impact studies in river systems.

Water-Handling Patterns and Associated Microbial Profiles in relation to Hygiene in Babati Town, Tanzania.

Introduction: In rapidly urbanizing centres in Tanzania, water supply infrastructure lags behind the speed of urbanization, affecting water availability and accessibility. We believe that inhabitants' access water using various ways which are characterizable and understanding them could inform about the risks to hygiene-related diseases. This study aimed at characterizing water-handling chains and their microbial profiles in Babati town to inform hygiene education policy and water supply planning. Methodology: A cross-sectional study design employing a proportional sampling for each of the 8 wards was conducted between November 2016 and March 2017. A total of 564 samples of water were collected using the USA EPA procedures from 37 randomly selected households. Water samples were collected from the common sources of water as well as from the downstream points to multiple storage containers. Using EPA membrane filtration techniques, two microorganisms were tested: fecal coliforms and Salmonella typhi. Results. Three water-handling chains/patterns in Babati town were determined, and they were as follows: (i) untreated-source-to-treated-reservoir-to-households (untrS2trR2HH) chain, (ii) untreated-source-to-untreated-reservoir-to-households (untrS2untrR2HH) chain; (iii) untreated-source-straight-to-households (untrS2HH) chain. In terms of the microbial profile, the most contaminated water-handling chain was the untreated-source-straight-to-households (untrS2HH). The number of users in these three chains was not statistically significantly different (p=0.5226), meaning that all people utilized the various chains almost equally, depending on the water situation. Most households (83%) did not treat their drinking water making those using the untreated-source-to-household chain (untrS2HH) most vulnerable to waterborne diseases. Conclusion: Determination of water-handling chains among the household is a novel approach which allows an understanding of the points at which highest fecal loading occurs. This approach therefore may inform the development of policies in the areas of household hygiene education, drinking water treatment, and water supply planning in urbanized towns in Tanzania and other developing countries.

Water defluoridation by Fe(III)-loaded sisal fibre: Understanding the influence of the preparation pathways on biosorbents' defluoridation properties.

Defluoridation properties of two Fe(III)-loaded plant biomass (Fe(III)-activated sisal fibre (Fe(III)-ASF) and post-alkalized Fe(III)-ASF (PA-Fe(III)-ASF)) distinguished by preparation pathways through exclusion/inclusion of post-alkalization are presented, with the aim of understanding the influence of post-alkalization in the preparation pathway to their fluoride removal properties. Findings reveal that PA-Fe(III)-ASF shows higher chemical stability with removal efficiency increasing towards acidic conditions, whereas Fe(III)-ASF manifests a lower chemical stability with removal efficiency increasing (in a wider pH range) with the increase in pH. This is attributable to the nature of the interactions between Fe(III) and the biomass surface functional groups. The removal efficiency by PA-Fe(III)-ASF has a strong positive correlation (0.98) to the surface charge/speciation induced by pH and the reverse is true for the Fe(III)-ASF. These findings therefore suggest that the principal fluoride removal mechanism is electrostatic interactions and ligand exchange for PA-Fe(III)-ASF and Fe(III)-ASF, respectively. Therefore, inclusion/exclusion of post-alkalization in preparation steps is an important aspect to consider in the production of Fe(III)-loaded biosorbents for water defluoridation for acquisition of specific defluoridation properties.

Mass transfer approach and the designing of horizontal subsurface flow constructed wetland systems treating waste stabilisation pond effluent.

Pilot-scale constructed wetlands (CWs) that allowed wastewater to flow with high interstitial velocities in a controlled environment were used to evaluate the possibility of using mass transfer approach to design horizontal subsurface flow constructed wetlands (HSSF-CWs) treating waste stabilisation ponds (WSPs) effluent. Since CW design considers temperature which is irrelevant in tropics, mass transfer approach could improve the design. HSSF-CWs were operated in batch recycle mode as continuous stirred tank reactors (CSTR) at different interstitial velocities. The overall removal rate constants of chemical oxygen demand (COD) at various interstitial velocities were evaluated in mesocosms that received pretreated domestic wastewater. The mean overall removal rate constants were 0.43, 0.69, 0.74 and 0.73 d-1 corresponding to interstitial velocities of 15.43, 36, 56.57 and 72 md-1, respectively. Results showed that the interstitial velocities up to 36 md-1 represented a range where mass transfer effect was significant and, above it, insignificant to the COD removal process. Since WSPs effluent has high flow rates and low organic load, it is possible to induce high interstitial velocities in a HSSF-CW treating this effluent, without clogging and overflow. The performance of these HSSF for tertiary treatment in tropical areas could be improved by considering flow velocity when designing.

Seasonal water chemistry variability in the Pangani River basin, Tanzania.

The stable isotopes of δ18O, δ2H, and 87Sr/86Sr and dissolved major ions were used to assess spatial and seasonal water chemistry variability, chemical weathering, and hydrological cycle in the Pangani River Basin (PRB), Tanzania. Water in PRB was NaHCO3 type dominated by carbonate weathering with moderate total dissolved solids. Major ions varied greatly, increasing from upstream to downstream. In some stations, content of fluoride and sodium was higher than the recommended drinking water standards. Natural and anthropogenic factors contributed to the lowering rate of chemical weathering; the rate was lower than most of tropical rivers. The rate of weathering was higher in Precambrian than volcanic rocks. 87Sr/86Sr was lower than global average whereas concentration of strontium was higher than global average with mean annual flux of 0.13 × 106 mol year-1. Evaporation and altitude effects have caused enrichment of δ18O and δ2H in dry season and downstream of the river. Higher d-excess value than global average suggests that most of the stations were supplied by recycled moisture. Rainfall and groundwater were the major sources of surface flowing water in PRB; nevertheless, glacier from Mt. Kilimanjaro has insignificant contribution to the surface water. We recommend measures to be taken to reduce the level of fluoride and sodium before domestic use.

Metallic iron for safe drinking water provision: Considering a lost knowledge.

Around year 1890, the technology of using metallic iron (Fe0) for safe drinking water provision was already established in Europe. The science and technology to manufacture suitable Fe0 materials were known and further developed in this period. Scientists had then developed skills to (i) explore the suitability of individual Fe0 materials (e.g. iron filling, sponge iron) for selected applications, and (ii) establish treatment processes for households and water treatment plants. The recent (1990) discovery of Fe0 as reactive agent for environmental remediation and water treatment has not yet considered this ancient knowledge. In the present work, some key aspects of the ancient knowledge are presented together with some contemporised interpretations, in an attempt to demonstrate the scientific truth contained therein. It appears that the ancient knowledge is an independent validation of the scientific concept that in water treatment (Fe0/H2O system) Fe0 materials are generators of contaminant collectors.

Wastewater treatment performance efficiency of constructed wetlands in African countries: a review.

In Africa, different studies have been conducted at different scales to evaluate wastewater treatment efficiency of constructed wetland. This paper aims to review the treatment performance efficiency of constructed wetland used in African countries. In the reviewed papers, the operational parameters, size and type of wetland used and the treatment efficiency are assessed. The results are organized and presented in six tables based on the type of wetland and wastewater used in the study. The results of the review papers indicated that most of the studies were conducted in Tanzania, Egypt and Kenya. In Kenya and Tanzania, different full-scale wetlands are widely used in treating wastewater. Among wetland type, horizontal subsurface flow wetlands were widely studied followed by surface flow and hybrid wetlands. Most of the reported hybrid wetlands were in Kenya. The results of the review papers indicated that wetlands are efficient in removing organic matter (biochemical oxygen demand and chemical oxygen demand) and suspended solids. On the other hand, nutrient removal efficiency appeared to be low.