Stabilization Ponds Research Articles

Biogas Potentials for Anaerobic Co-Digested Rumen Contents and Sewage Sludge

Sewage sludge (SS) and rumen contents (RC) are produced daily in waste stabilization ponds and abattoirs respectively as organic wastes. However, these wastes could pose a threat to the environment if not properly managed hence, this research investigated the potentials of these wastes in generating biogas. This was achieved by digesting different SS/RC ratios anaerobically for 30days and recording the biogas produced under mesophilic condition. The SS and RC were obtained from Ahmadu Bello University (ABU) waste stabilization pond and cattle (Bos indicus) respectively, while the SS/RC ratios considered were 1:0, 0:1, 1:1, 1:2 and 2:1. Results showed that the co-digested organic wastes produced more biogas compared to mono-digestions of equivalent volumes of SS (1:0) and RC (0:1). This is because the recorded daily biogas potentials for SS/RC ratios 1:0, 0:1, 1:1, 1:2 and 2:1 were 12.77, 19.59, 21.79, 23.85 and 20.45ml per gram of TS added respectively. Hence, it was concluded that biogas potential for SS improved by 70.63%, 86.77% and 60.14% when co- digested with RC at SS/RC ratios 1:1, 1:2 and 2:1 respectively, while that of RC improved by 11.23%, 21.75% and 4.39% at SS/RC ratios 1:1, 1:2 and 2:1 respectively.

Potential of Macrophytes for Wastewater Remediation with Constructed Floating Wetlands in Cold Climates

Nature-based, low technology wastewater treatment systems can benefit small and remote communities. Adding a constructed floating wetland (CFW) to waste stabilization ponds can enhance treatment efficacy at low cost, depending on appropriate macrophytes. In cold climates, harsh growing conditions may limit CFW success, requiring research under-ambient field conditions. Seven native macrophytes were assessed for the growth, biomass production, and root and shoot uptake of potential contaminants of concern from municipal wastewater in a facultative stabilization pond in Alberta, Canada. All macrophytes established. Scirpus microcarpus had high nitrogen and phosphorus in roots and shoots and phytoextraction potential. Metal and trace elements were highest in Glyceria grandis, Beckmannia syzigachne, and Scirpus microcarpus, mostly greater in roots than shoots, indicating phytostabilization. Tissue contaminant concentrations did not always indicate high contaminant accumulation in the CFW. Total uptake per unit area was greatest for Glyceria grandis, although chromium and molybdenum were greatest in Beckmannia syzigachne and Carex aquatilis, respectively. Beckmannia syzigachne and Scirpus microcarpus have potential for phytoremediation if biomass per unit area is increased. Species variability is high for contaminant accumulation and biomass; in unpredictable climates and wastewaters with suites of contaminants, different macrophytes for wetland water treatment systems are recommended.

Geo-hazards assessment of the new-found industrial communities: an example from the 10th of Ramadan Industrial Region, Egypt

The impacts of Geo-hazard events are main obstacles to the use of land in numerous arid and semi-arid provinces of the World. Furthermore, the various activities of industrial communities, such as Egypt's 10th Ramadan Industrial Region (10th RIR), are the most dangerous examples of waste's impact on soil, surface water, and groundwater. The current study uses image processing and GIS tools to identify, delineate, monitor, and assess some of the environmental hazards caused by both human and natural activities in the 10th RIR. The findings revealed that there are rapid changes in land cover, which could be attributed to both anthropogenic and natural activities. Furthermore, the results revealed that waterlogging, salt-affected soils, water pollution, and flash floods were the most serious environmental threats to the 10th RIR. The obtained geo-hazard map showed that the 10th RIR has high flash flood hazards zones that are geospatially distributed in the southern parts of the Wadi Gafra basin and the western parts of 10th of Ramadan City. Furthermore, salinized soil zones are viewed as geospatially restricted zone in the eastern portion of 10th of Ramadan City and/or near the oxidation ponds. Additionally, vast areas of highly contaminated groundwater exist beneath industrial, urban, and oxidation pond zones. The current work provides decision-makers with numerous mitigation measures and recommendations required to minimize the impacts of geo-environmental hazards endangering the 10th RIR.

Emerging contaminants in conventional and advanced biological nutrient removal based wastewater treatment plants in India- insights into the removal processes

Emerging contaminants (ECs) in the environment are a cause of concern due to their potential toxic effects. The study investigates the fate of 20 ECs covering a wide range of physical-chemical properties in ten full-scale municipal wastewater treatment plants (WWTPs). The plants were based on conventional technologies such as waste stabilization pond, upflow sludge blanket reactor, activated sludge process, and biological nutrient removal-based technologies such as anoxic-aerobic process, anaerobic-anoxic-aerobic process, biodenipho process, sequencing batch reactor, and densadeg-biofor process. Covering all the wastewater and sludge treatment lines, the mass balance approach was followed to investigate the fate of ECs at each treatment stage. The amount of ECs entering and leaving the WWTPs ranged from 0.82 to 11.94 kg/day and 0.027 to 0.70 kg/day, respectively. Antibiotics showed limited removal and were detected in the 0.006 to 0.18 kg/day range. The ECs were mainly detected in the aqueous phase in all the treatment steps. However, the contribution from the particulate and sludge phase cannot be neglected. The sorption of ECs on sludge depended on the sludge's characteristics. It was found to be the highest in the primary sludge. The measured sorption coefficient indicated that both hydrophobic and electrostatic interactions of ECs with the sludge are insufficient in explaining the sorption behaviour of a contaminant. The mass balance studies show biodegradation as the major removal pathway in all the WWTPs. The study provides the environmental mass load of ECs from Indian WWTPs. It will help understand the removal mechanisms of ECs in different types of wastewater treatment techniques.

Upgrade of waste stabilization ponds to improve effluents for reuse purposes

AbstractWaste stabilization pond (WSP) systems exist in many countries affected by climate change causing increasing demand for irrigation water. There is little long-term experience with WSP in Africa, and thus, this study provides a comprehensive investigation of a WSP in Namibia. One of its treatment trains was upgraded with mechanical and anaerobic pre-treatment, and post-treatment and compared to a second train without upgrades. The pre-treatment showed positive results on COD, TSS and partially pathogen removal. E. coli were reduced to the new EU reuse standard of 1,000 MPN/100 mL for fodder irrigation, P. aeruginosa stagnated and Enterococci levels increased. The main pathogen reduction happened during pre-treatment and in the baffled facultative pond. In contrast, the post-treatment only reduced 5% of algae-based chlorophyll-a. Among the top 20 genera, Pseudomonas was most dominant. With different upgrades, hygiene requirements especially for restricted fodder irrigation can be reached. At the same time, high total tCOD and TN effluent values did not meet different reuse standards. But as the tCOD mainly consists of algae, adding biomass and TN fertilizer to the barren soil, it raised the question if all parameters set in the standards are applicable for WSP or should be adapted to their specific purpose.

Inlet retrofitting improves the hydraulic performance of a waste stabilization pond

Wastewater is transitioning from being viewed as a waste to being utilized as a resource in the production of reclaimed water. Reclaimed water, obtained through waste stabilization pond treatment technologies, has the potential to offset potable water needs for irrigation purposes as well as fertilizers for crop growth. In developing countries, where waste stabilization ponds are widely used, a major issue is the lack of maintenance which can lead to considerable amounts of sludge piled at the bottom of the pond. This sludge accumulation reduces the treatment capacity of the waste stabilization pond and possibly, the treatment efficiency which is vital for reuse purposes. In cases for which desludging of the pond is a challenge, retrofitting the pond inlet can offer an alternative to improve pond hydraulic performance. In this study, two inlet retrofit geometries are investigated in a waste stabilization pond with significant sludge accumulation using computational fluid dynamics. It is seen that retrofitting the pond with a three-way pipe inlet increases the mean residence time of the pond from 21.9 days to 25 days over a single pipe inlet while significantly reducing the strength of short-circuiting.

Characterization of novel proteases identified by metagenomic analysis from dairy stabilization ponds.

Cheese whey is the main by-product of dairy industries. It is used as a raw material for other value-added products, like whey protein concentrate. By using enzymes, this product can be further treated to obtain new higher value products, like whey protein hydrolysates. Proteases (EC: 3.4) represent a large segment of industrial enzymes, since they are used in several industries, including food. In this work, we describe three novel enzymes identified using a metagenomic approach. Metagenomic DNA from dairy industry stabilization ponds were sequenced, and the predicted genes were compared against the MEROPS database, focusing on families commercially used to produce whey protein hydrolysates. From a total of 849 candidates, 10 were selected for cloning and expression and three showed activities with both the chromogenic substrate, azocasein, and whey proteins. Particularly, Pr05, an enzyme from the yet uncultured phylum Patescibacteria, showed activity that is comparable to a commercial protease. All these novel enzymes could represent an alternative for dairy industries to produce value-added products from industrial by-products. KEY POINTS: • Over 19,000 proteases were predicted in a sequence-based metagenomic analysis. • Three proteases were successfully expressed and showed activity with whey proteins. • The enzyme Pr05 showed hydrolysis profiles of interest for food industry.

Nonbacterial Microflora in Wastewater Treatment Plants: an Underappreciated Potential Source of Pathogens.

Wastewater treatment plants (WWTPs) receive and treat large volumes of domestic, industrial, and urban wastewater containing pathogenic and nonpathogenic microorganisms, chemical compounds, heavy metals, and other potentially hazardous substances. WWTPs play an essential role in preserving human, animal, and environmental health by removing many of these toxic and infectious agents, particularly biological hazards. Wastewater contains complex consortiums of bacterial, viral, archaeal, and eukaryotic species, and while bacteria in WWTP have been extensively studied, the temporal and spatial distribution of nonbacterial microflora (viruses, archaea, and eukaryotes) is less understood. In this study, we analyzed the viral, archaeal, and eukaryotic microflora in wastewater throughout a treatment plant (raw influent, effluent, oxidation pond water, and oxidation pond sediment) in Aotearoa (New Zealand) using Illumina shotgun metagenomic sequencing. Our results suggest a similar trend across many taxa, with an increase in relative abundance in oxidation pond samples compared to influent and effluent samples, except for archaea, which had the opposite trend. Additionally, some microbial families, such as Podoviridae bacteriophages and Apicomplexa alveolates, appeared largely unaffected by the treatment process, with their relative abundance remaining stable throughout. Several groups encompassing pathogenic species, such as Leishmania, Plasmodium, Toxoplasma, Apicomplexa, Cryptococcus, Botrytis, and Ustilago, were identified. If present, these potentially pathogenic species could be a threat to human and animal health and agricultural productivity; therefore, further investigation is warranted. These nonbacterial pathogens should be considered when assessing the potential for vector transmission, distribution of biosolids to land, and discharge of treated wastewater to waterways or land. IMPORTANCE Nonbacterial microflora in wastewater remain understudied compared to their bacterial counterparts despite their importance in the wastewater treatment process. In this study, we report the temporal and spatial distributions of DNA viruses, archaea, protozoa, and fungi in raw wastewater influent, effluent, oxidation pond water, and oxidation pond sediments by using shotgun metagenomic sequencing. Our study indicated the presence of groups of nonbacterial taxa which encompass pathogenic species that may have potential to cause disease in humans, animals, and agricultural crops. We also observed higher alpha diversity in viruses, archaea, and fungi in effluent samples than in influent samples. This suggests that the resident microflora in the wastewater treatment plant may be making a greater contribution to the diversity of taxa observed in wastewater effluent than previously thought. This study provides important insights to better understand the potential human, animal, and environmental health impacts of discharged treated wastewater.

Performance of municipal waste stabilization ponds in the Saharan desert (Morocco)

Abstract The majority of cities in the Saharan territory of south Morocco utilize waste stabilization ponds (WSPs) for municipal wastewater treatment because of their relatively low capital, operational costs, and minimal complexity. New national effluent quality regulations have been implemented in Morocco, and they will be applied to all treatment systems. In this study, we chose three cities that are located in the Saharan area characterized by an arid climate and water scarcity. They are facing the challenges of rapid urbanization and the need to improve wastewater treatment and management. Treatment performance is impacted by community water use, pond design, and climate. The performance evaluation concerns seven physicochemical parameters during the year 2020. Monitoring results showed that WSPs in this climate can achieve removal rates between 75% and 85% for organic pollution and total suspended matter, but were challenged to produce effluent quality that meets reuse standards. Performance and statistical analysis have been done and confirm the existence of correlations between these parameters and the climate of the region. For the improvement of the quality of these waters, it is legitimate to upgrade the three WSPs with a tertiary treatment with maturation ponds.

Effect of sunlight on three stratifications of waste water from a waste stabilization pond

Experimental studies on stratification were conducted on a waste stabilization pond system at the University of Nigeria, Nsukka, Nigeria. This was done to ascertain the effect of stratification due to sunlight on pond parameters. An experimental approach was adopted which involved pouring wastewater into a glass column apparatus and exposing to sunlight for 7, 14, and 21 days. The statues of 16 physicochemical and microbiological parameters were investigated in the three strata under consideration. Analysis of the samples collected at depths A, B and C, 30cm apart, starting from the top indicated different values of temperature, pH, and nutrients. Maximum values of temperature (32.9 0C), pH (7.9), turbidity (3.46 NTU), and iron (1.86 mg/l), were recorded at the top layer; while the concentration of conductivity (906 μS/cm), total dissolved solids (589 mg/l), BOD5 (400mg/l), ammonia (290 mg/l), total coliform (126,000 cfu/100ml), and E. Coli (99,000 cfu/100ml) were highest at bottom layer. Conductivity, total dissolved solids, turbidity, iron, phosphorus and nitrates fell within World Health Organization (WHO) guidelines. A combination of sunlight with high pH and oxygen concentrations is needed for sunlight to have very significant effects. It is recommended that WSPs be designed with the consideration given to pond dimensions that will provide a wider surface area for sufficient sunlight and oxygen to be acquired.

Biogas effluent treatment by Landoltia punctata for starch biomass production

Due to the high potential of using Landoltia punctata in biogas effluent treatment and starch accumulation, three integrated processes were proposed: (1) bioethanol production from duckweed, (2) biogas production from vinasse, and (3) biogas effluent treatment with sequentially increasing starch-rich duckweed biomass. This recent work focuses only on the third process, which involves the treatment of wastewater from biogas effluent and the production of L. punctata with high starch content. L. punctata showed a significantly higher TKN removal and biomass production than Lemna aequinoctialis. After nine days of wastewater treatment and five days of starch accumulation, L. punctata grew by 4.3 g/m2/day, with 44.4% starch content. NH3, NH4+, and PO43− in the biogas effluent were rapidly utilized in the first three days for L. punctata’s growth. The upregulation of AGPase genes in the starch biosynthesis pathway was observed when the environmental conditions changed in both nutrient starvation and population reduction. Production of starch-rich L. punctata using biogas effluent is a sustainable feedstock for the bioethanol process. Moreover, L. punctata-based stabilization pond is a promising technique for biogas effluent treatment.

Analysis of the Sludge Settling Behavior of the Kibendera Waste Stabilization Ponds in Ruiru, Kenya

Waste Stabilization Ponds (WSP) provide both cost-effective and high-performance wastewater treatment benefits in the tropical regions. The 3-month sludge settling behavior in the Kibendera WSP in Ruiru, Kenya, was studied between July and September 2022. The study aimed at determining the sludge volume index (SVI) and hindered settling velocity during the dry weather flow regime. Based on these experimental data, Vesilind Model was used to characterize the settling behavior in the anaerobic and primary facultative ponds. Whereas Standard Methods for the examination of water and wastewater were used to determine the total suspended solids (TSS) concentrations in the ponds, batch column settling tests were used to generate the batch settling curves for each pond. Generally, good settling behavior characterized by SVI values of less than 150 mL/g was observed during the study period. Highest settling velocities of 1.16 m/hr and 1.22 m/hr were recorded in the anaerobic and primary facultative ponds respectively for TSS concentrations of 0.6 g/L and 0.416 g/L. Optimal maximum velocity (<i>V_max</i>) values of 3.42 m/hr and 1.78 m/hr were observed in the anaerobic and primary facultative ponds respectively. The corresponding optimal model parameters (n) describing the measured data accurately were 0.47 L/g and 0.51 L/g respectively. The model parameters so obtained may be useful in characterizing the sedimentation behavior in the WSP during the dry weather flow regimes.

Enzymological Analysis of Carps (Cyprinus carpio and Labeo rohita) Cultured in Tropical Domestic Sewage Oxidation Ponds

Enzymological Analysis of Carps (Cyprinus carpio and Labeo rohita) Cultured in Tropical Domestic Sewage Oxidation Ponds

Using geochemical models to delineate the relationship between the Pleistocene aquifer groundwater and the oxidation ponds at El-Sadat city, Egypt

This study aims to assess the risk of the wastewater plume from the oxidation ponds contaminating the underneath shallow groundwater aquifer. The study area is an industrial city comprised of three main zones: industrial, populated, and agricultural. The study area is bordered on the eastern side by a wastewater pond and the Rosseta Nile river branch. The geochemical investigation is based on the determination of groundwater salinity, major ions, nitrogen compounds (NH4−, NO2−, NO3−), phosphate (PO43−), heavy metals, and the isotopic content (δ18O and δ2H) as well as the geochemical groundwater modeling. The results show most groundwater samples (50%) in the study area are freshwater, 31% are marginal saline water, and 18% are brackish. Higher nitrogen and PO43− compound concentrations are found in the shallow groundwater close to the oxidation ponds and populated zone. The δ18O and δ2H in the Quaternary groundwater is relatively depleted; they range from −2.1 to 2.3‰ and −7 to 21‰, respectively. The integrations of the geochemistry and isotopes show that the Pleistocene aquifer receives considerable recharge percent (14–56%) from the Rosseta Nile river branch and has been polluted due to the seepage from the oxidation ponds (seepage percent range: 0.6–3.6%). The results suggest that excessive fertilizer usage in the agricultural zone, seepage from oxidation ponds into the subsurface aquifer, and the anthropological effects of population size and industrial zones all contribute to the decline in groundwater quality. The highly vulnerable groundwater sites extend from the northeastern areas close to the oxidation ponds and the southwestern areas close to the industrial and populated zones.

Fate and removal of pesticides in solid and liquid phases of metropolitan, urban and rural-scale wastewater treatment plants

In this study, the change of occurrence, distribution, seasonal variation and removal of pesticides, atrazine (ATZ), chlorpyriphos (CPR) and chlorfenvinphos (CFV), were investigated both in liquid and solid phases of three different types of wastewater treatment plants (WWTPs). Treatment configurations of the studied WWTPs consist of a metropolitan advanced biological treatment system (4-stage Bardenpho), urban-scale waste stabilization pond (WSP) and rural-scale horizontal subsurface flow constructed wetland (HSSCW).ATZ removal efficiencies (59.8 %–92.4 %) were higher than CPR and CFV removal efficiencies at all WWTPs. CPR and CFV are removed at 78.5 % and 53.1 % efficiency, respectively, from the influent of advanced biological treatment system. CPR and CFV removals were 21.6 and 22.7 % at WSP, respectively.One of the important findings is that ATZ and CFV were removed at higher percentages in primary treatment than in biological treatment in advanced biological WWTP. Sorption onto sludge has been evaluated as an effective removal mechanism for pesticide elimination, at least as much as biodegradation/biotransformation. All investigated pesticides were detected in higher concentrations in primary sludge (168.8–399.5 μg/kg) compared to secondary sludge (21.9–146.3 μg/kg) in advanced biological WWTP and in facultative sludge (447.8–1044.7 μg/kg) compared to anaerobic sludge (250.0–613.0 μg/kg) in WSP. It was determined that ATZ was the most treated compound in the liquid phase under anaerobic conditions among the studied pesticides. In line with these results, approximately 45 % removal efficiency was determined for CPR and CFV in the anaerobic digestion process present in advanced biological WWTP.

Sustainable Co-Management of Acid Mine Drainage with Struvite Synthesis Effluent: Pragmatic Synergies in Circular Economy

Herein, the alkaline supernatant of a struvite recovery system from municipal wastewater was successfully co-managed with acid mine drainage (AMD). Various ratios (v/v) of AMD to struvite supernatant were examined, and the quality of the passively co-treated effluent and of the generated sludge were examined using state-of-the-art analytical techniques including ICP-OES, FE-SEM/FIB/EDX, XRD, XRF, and FTIR. The optimum ratio was 1:9, where metals and sulphate were largely removed from AMD, i.e., from higher to lower score Fe (~100%) ≥ Pb (~100%) ≥ Ni (99.6%) ≥ Cu (96%) ≥ As (95%) ≥ Al (93.7%) ≥ Zn (92.7%) &gt; Ca (90.5%) &gt; Mn (90%) ≥ Cr (90%) &gt; sulphate (88%) &gt; Mg (85.7%), thus implying that opportunities for mineral recovery could be pursued. The pH of the final effluent was regulated to acceptable discharge levels, i.e., 6.5 instead of 2.2 (AMD) and 10.5 (struvite supernatant), while a notable reduction in the electrical conductivity further implied the attenuation of contaminants. Overall, results suggest the feasibility of the passive co-treatment of these wastewater matrices and that opportunities for direct scaling up exist (e.g., using waste stabilization ponds). Furthermore, apart from the initial recovery of struvite from municipal wastewater, metals could also be recovered from AMD and water could be reclaimed, therefore introducing circular economy and zero liquid discharge in wastewater treatment and management.

Phosphorus uptake and accumulation in Chlamydomonas reinhardtii: Influence of biomass concentration, phosphate concentration, phosphorus depletion time, and light supply

The model microalga Chlamydomonas reinhardtii was cultivated under P depleted and P repleted conditions to test the influence of dissolved P concentration (0–20 mg-P·L−1), initial algal biomass concentration (0.17–0.57 g-DW·L−1), P-depletion time (1 h – 4 days) and light supply (continuous illumination versus darkness) on phosphate uptake rate (mg-P·h−1·L−1) and the cellular P content (as %P of dry cell mass). Dissolved P concentration positively influenced cellular P content, while biomass concentration and P-depletion time did not. Biomass concentration and P-depletion time instead positively influenced P uptake rates. Light supply neither influenced cellular P content nor P assimilation. These findings evidence that depleting the cells at high initial biomass concentration could enhance P removal during wastewater treatment in waste stabilization ponds. Practically, these findings imply that high P removal from wastewater could be achieved by exposing ‘concentrated’ P-depleted biomass to P-laden influent in a relatively short contact-time reactor and subsequently harvesting and removing the resultant P-rich biomass. This stage would be followed by normal biomass growth in larger ponds which depletes the remaining P, with this biomass being harvested and returned to the contact tank for P removal.

Performance of constructed floating wetlands in a cold climate waste stabilization pond

Effectiveness of constructed floating wetlands (CFWs) is largely unknown for wastewater treatment in cold climates. An operational-scale CFW system was retrofitted into a municipal waste stabilization pond in Alberta, Canada. During the first year (Study I), insignificant performance was recorded for water quality parameters, although phyto-uptake of elements was evident. In Study II, doubling of the CFW area and addition of underneath aeration promoted plant uptake of elements, including nutrients and metals, following significant pollutant reduction in the water; 83 % of chemical oxygen demand, 80 % of carbonaceous biochemical oxygen demand, 67 % of total suspended solids, and 48 % of total Kjeldhal nitrogen. A mesocosm study, conducted in parallel to the pilot scale field study, confirmed the impact of both vegetation and aeration on water quality improvement. The phytoremediation potential was linked to accumulation within plant shoot and root biomass and was confirmed by mass balance. Bacterial community analyses reflected that heterotrophic nitrification, aerobic denitrification, complete denitrification, organic matter decomposition, and methylotrophy were dominant mechanisms in the CFW, likely resulting in successful transformation of organics and nutrients. CFWs appear to be a viable ecotechnology to treat municipal wastewater in Alberta; however, larger and aerated CFW systems are recommended to achieve maximum remediation. The study aligns with the United Nations Environment Program to scale up restoration of degraded ecosystems, and to improve conditions for water supply and biodiversity following recognition of 2021–2030 as the Decade on Ecosystem Restoration.

Evaluation of a Three-Dimensional Hydrodynamic and Water Quality Model for Design of Wastewater Stabilization Ponds

A three-dimensional coupled hydrodynamic and water quality model (Deflt3D-WAQ) was applied to evaluate the ability of a computational simulation to reproduce seasonal water quality conditions over a seven-month period in a wastewater stabilization pond located in eastern Ontario, Canada. Trends in effluent nutrient concentrations, pH, and dissolved oxygen were visually reproduced, and root-mean square errors, in comparison with weekly observations (alkalinity, 43 gHCO3 m−3; dissolved oxygen, 4.0 gm−3; NO3, 2.2 gN m−3; PO4, 0.10 gP m−3; NH4, 0.14 gN m−3; pH, 0.65), were consistent with literature values. Three phytoplankton groups (green algae, diatoms, and flagellates) were also simulated. The calibrated model was extended to investigate the effects of changes in pond design on treatment efficiency, including removing the baffle, increasing the pond depth, increasing wind sheltering, and relocating the influent pipe from the pond bottom to the surface. Increasing the pond depth and wind sheltering reduced vertical mixing, sequestering nutrients near the sediments and improving effluent water quality. Removing the baffle had no impact on removal efficiency, and relocating the inlet to the surface reduced pond efficiency. Three-dimensional biogeochemical models thus provide a virtual process-based means for testing pond prototype design.

Generation of Electricity by Using Microbial Fuel Cell Prototype Fed by Sewage: Case Study at the University of Dar es Salaam

The access to electricity is still not reliable in Tanzania. Whilst, there are several locations within the country that have wastewater cites that are not economically used to produce electricity. At the University of Dar es Salaam (UDSM), there are main grid power, and few scattered solar panels. This study was intended to bridge the divide between the current increasing power demands of the UDSM by exploiting not so much used sources, such as electric energy from wastewater. This study was undertaken to develop a Microbial Fuel Cell (MFC) prototype fed by sewage in Dar es Salaam, for electricity generation using cost effective materials for the cathode compartment. The collection of samples took place using sewage substrates from the UDSM oxidation ponds. The untreated sewage was collected from oxidation ponds. Preliminary experiments were carried out to identify the cathode and substrate that produced better results in terms of volts and current output. Aluminium produced the most desirable results compared to copper, stainless steel and mild steel in all the substrates. On the other hand, untreated sewage with aluminium/carbon electrodes produced higher voltage and current compared to treated sewage with the same electrodes. Thereafter, a prototype of the MFC was developed by connecting three single chambered cells in series of 628 cm3 volume of untreated sewage with aluminium and carbon electrodes. The prototype generated a stable voltage of 1.73 V and a current of 0.07 mA recorded for a period of one hour. The power generated was enough to light a 6.25 mW LED bulb of 25 mA across a 100 Ω resister. Therefore, untreated sewage produced more power in MFCs with aluminium/carbon electrodes compared to the other tested materials.&#x0D; Keywords: Aluminium electrodes, charcoal electrode, alternative energy source, wastewater