Suitable Treatment Technology Research Articles

Investigating the Electrocoagulation Treatment of Landfill Leachate by Iron/Graphite Electrodes: Process Parameters and Efficacy Assessment

Electrocoagulation is a widely used method for treating leachate since it is cost effective and eco-friendly. In the present study, the electrocoagulation process was employed to remove chemical oxygen demand (COD), NH4+, total dissolved solids (TDS), total suspended solids (TSS), turbidity, and color from landfill leachate. At first, lime was used as a pretreatment, then the Fe/Gr and Ti/PbO2/steel electrodes were used, and the optimum electrode was selected. Afterwards, the effects of some variables, including pH, current density, temperature, the inter-electrode distance, and the type of electrolyte were investigated. Results showed that COD, NH4+, TSS, TDS, electrical conductivity (EC), turbidity, color, and pH of effluent pretreatment chemical reached 22,371, 385, 884, 21,820 (mg/L), 13.8 (ms/cm3), 1355 (NTU), 8500 (TCU) and 10, respectively (the removal efficiency was 0, 20.37, 32.4, 61.99, 59.18, and 56.6 percent). With the Fe/Gr electrode, the optimal condition was observed as follows: pH of 7.5, current density of 64 mA/cm2, inter-electrode distance was equal to 1.5 cm, temperature at 20 °C, and retention time 2–4 h. Overall, the electrocoagulation with the Fe/Gr electrode was a suitable technology for landfill leachate treatment due to its effectiveness for the removal of both COD and NH4+, with advantageous performance indicators.

Cost Estimations of Water Pollution for the Adoption of Suitable Water Treatment Technology

This study analyzed the cost implications of using suitable technologies and the cost of inaction when addressing water pollution. This was achieved by developing three main models for the costs (model one) and benefits (model two and model three). The first model accounts for the operational costs of adopting suitable technologies, namely the use of diatomaceous earth for textile wastewater treatment. The second model analyzed the cost of inaction through analyzing the cost of treatment for water pollution-related diseases for the affected population. The occurrence and cost of treatment for three diseases, namely diarrhea, amoebiasis and bacterial infection, were used as indicators of water pollution in the area. The third model included the contingent valuation method (CVM) data on the willingness to pay for environmental restoration of the surveyed population. The benefit–cost ratio (BCR) of the resulting data from the three models were used to highlight the economic viability of the proposed project. A BCR of (0.67) for the cost of the proposed project versus the benefits of the project on human health using data from one hospital was obtained. There is a high possibility that the real BCR would increase if more data from other hospitals or other diseases were included. The results imply that the use of D.E can be considered a good candidate for treating wastewater. To thoroughly discuss the BCR of treating wastewater from one factory, the BCR of the proposed restoration project along River Sosiani, and the value of using DE as suitable technology, more studies are needed to evaluate the unaccounted costs and benefits for accurate economic estimations of the proposed project. The outcome of the study is a framework of numbers and figures that can be presented to decision makers and policy makers as critical information when making decisions.

Degradation efficiencies of 2,4,6-TCP by Fe0-based advanced oxidation processes (AOPs) with common peroxides.

Degradation of 2,4,6-trichlorophenol (2,4,6-TCP) by zero-valent iron (ZVI) activating three common peroxides (peroxymonosulfate (PMS), hydrogen peroxide (H2O2), and peroxydisulfate (PS)) was investigated. The effects of ZVI dosage, peroxides concentration, initial pH, and Cl- concentration were examined. The 2,4,6-TCP degradation efficiencies by Fe0/peroxides (PMS, H2O2, PS) were compared. Results showed that the order for degradation efficiency was H2O2≥PMS>PS. The degradation efficiency of 2,4,6-TCP in ZVI/peroxides systems were optimal at c(Ox) = 1 mmol•L-1; c(Fe0) = 0.1 g/L; initial pH = 3.2. Additionally, pH had a vital effect on 2,4,6-TCP degradation. At pH<3.2, ferrous play a vital role in all reaction, and accelerate the reaction rate rapidly. The existence of NaCl showed different results in the four systems. Chloride had little effect on 2,4,6-TCP degradation when chloride concentration at 5 mM, whereas the presence of 300 mM chloride significantly accelerated the degradation of 2,4,6-TCP from 72.7% to 95.2% in ZVI-PMS system. Notably, the other three systems showed opposite results. In contrast, the AOX (Absorbable Organic Halogen) values were highest in ZVI-PMS-Cl- system, due to the formation of lots of refractory chlorinated phenols as identified by GC-MS. These findings are good for choosing the most suitable technology for chlorophenol wastewater treatment.

Experimental investigation of designed solar parabolic concentrator based desalination system for textile industry wastewater treatment

The escalation in demand for textile products increased the use of fresh water and treatment of wastewater; which escalates the search for suitable and energy-efficient technology for wastewater treatment. Solar assisted technology ( i.e. solar desalination) for the textile industry wastewater treatment is proved to be an affordable technology. The only drawback of solar desalination is its low productivity which is the major hindrance in the global acceptance of the system. In the present study, an ingenious improvement in form of a parabolic concentrator-based solar desalination system (PCB-SDS) is designed to overcome low productivity, and the simultaneous use of source textile industry wastewater for its treatment makes this study more realistic. The performance of the designed system was examined for three different brine depths i.e. 20%, 40%, and 60% for two different processing step i.e. Dyeing and Degumming. System performance was evaluated in terms of energetic, exergetic, pollutant removal, and economic analysis. The maximum output of the system was found to be around 7440 and 8330 mL/day on clear sunny days with textile dyeing wastewater (TDyWW) and textile degumming wastewater (TDgWW) at 60% depth respectively. Daily average energy and exergy efficiency of system varies in the range 39.8–51.9 and 3.6–4.8% respectively. The degumming wastewater shows 85% COD removal, whereas, around 90% of TDS and hardness removal was also recorded. The dyeing processed wastewater showed 80% COD removal efficiency, ≅90% TDS, and hardness removal. The cost per liter of distillate output produced from designed PCB-SDS was found to be 0.014 $/L.

Glycine-hydrochloric acid buffer promotes simultaneous U(VI) reduction and bioelectricity generation in dual chamber microbial fuel cell

BackgroundA large amount of uranium-containing wastewater (UCW) is produced in the mining and smelting of uranium ore and the use of uranium. If UCW is not properly treated, it will pose a huge threat to ecology and human health. MethodsHere, microbial fuel cell (MFC) technology was introduced to removal uranium from UCW and generate bioelectricity simultaneously. To solve the low efficiency of MFC in separation uranium from UCW and to improve MFC's performance, carbon brush cathode was immersed in a new type of catholyte composed of only UCW and a glycine-hydrochloric acid buffer (GHAB). COD, pH, initial U(VI) concentration, and external resistance were all involved to obtain optimal operating conditions. SEM, EDS and XPS analyzes were conducted to investigate the removal mechanism. Significant findingsThe results indicate that the U(VI) removal efficiency was maintained above 99.0%, which was at least 22.0% higher than that without the addition of GHAB to the catholyte. Even when the U(VI) concentration in the catholyte was relatively low (20.0 mg/L), the maximum power density (Pmax) of the MFC reached to 269.5 ± 20.0 mW/m2. A high U(VI) removal efficiency and a high steady-stable performance were also achieved by the MFC even though the catholyte was extremely acidic (pH=2). Furthermore, the reduction of dissolved U(VI) to precipitated U(IV) and/or U(V) was proved to be the main reason for the removal of uranium. The present study has successfully verified that MFC with GHAB in UCW catholyte is a suitable technology for UCW treatment with high electricity generation and high U(VI) removal rate.

Degradation of amoxicillin with sono, photo, and sonophotocatalytic oxidation under low-frequency ultrasound and visible light

The presence of pharmaceutically active compounds in aquatic bodies is a global concern, and suitable treatment technologies are required. In this study, the efficacy of photocatalytic, sonocatalytic, and sonophotocatalytic oxidation processes for the degradation of amoxicillin (AMX) was investigated using visible light with N doped TiO2 (N–TiO2) nanoparticles as the catalyst and low-frequency ultrasound in a novel multifrequency reactor. The influence of different operational parameters on the extent of AMX degradation was studied. Sonophotocatalytic oxidation was found more efficient for AMX degradation when compared to photocatalysis or sonocatalysis alone, and may be due to the reduced bandgap of the catalyst, enhanced cavitation effect due to the presence of the solid catalyst, and improved mass transfer of pollutants. AMX degradation during sono, photo, and sonophotocatalytic oxidation processes was in good agreement with pseudo-first-order kinetics. Empirical kinetic models were also developed using multiple linear regression for predicting the degradation efficiency accounting for the operational parameters. Scavenger experiments suggested that •OH radicals largely contributed to AMX degradation, and a plausible mechanism for degradation was proposed. Further, possible degradation pathways for all three treatment processes are also proposed after identifying the degradation products.

Environmental impact and optimization of lake dredged-sludge treatment and disposal technologies based on life cycle assessment (LCA) analysis

Baiyangdian Lake is the most important natural water body in North China and is having a dredging project to remediate serious endogenous pollution from sediments. How to reduce the secondary environmental impact in the process of dredged-sludge treatment and disposal is of great significance. Four typical dredged-sludge treatment technologies were evaluated based on comprehensive life cycle environmental and economic analysis in this paper, and recommendations are put forward to selecting suitable treatment technology for dredged-sludge with heterogeneous pollution. The LCA results indicated that land use process is a preferable approach for less polluted dredged-sludge due to simple steps and low cost. However, the environmental burden derived from land use will obviously increase with the extent of the dredged-sludge pollution, especially depends on the content of heavy metals. Comparatively, organochlorine pesticides in dredged-sludge generate a negligible environmental impact because of their trace concentration. Besides, the manufacture of non-fired brick or water storage clay is an effective treatment technology for dredged-sludge with high pollution to reduce toxic environmental impacts owing to the immobilization and stabilization of heavy metals, although it has high economic costs and consumes a large amount of energy and materials. Moreover, it is worth noting that polyacrylamide may be not an excellent conditioner for dredged-sludge dewatering because of the apparent contribution to human toxicity and freshwater aquatic ecotoxicity impact. Overall, this study highlighted and concluded how to select and optimize the adoption of suitable technologies to reduce environmental risks generated from the treatment and disposal of dredged-sludge.

A novel Pythagorean fuzzy combined compromise solution framework for the assessment of medical waste treatment technology

Medical waste management (MWM) is extremely important to protect the general public and environment. Medical practitioners have used various medical waste treatment technologies (MWTTs) for MWM. In this study, a few treatment technologies (TTs) namely Incineration, Chemical disinfection, Microwave, Autoclaving and Reverse Polymerization are considered as alternatives. Further, each of the TTs is assessed based on the technology and its operation, social acceptance, environmental protection, total cost, and health hazards. Finally, the most suitable technology is selected. The process of selecting the most suitable TT can be regarded as a multi-criteria decision-making (MCDM) problem owing to the involvement of several factors. During this process, the decision experts have some uncertainty and ambiguity to measure the qualitative and quantitative opinions in the selection of best alternative over different criteria. To address this issue, a new Pythagorean fuzzy-based decision-making methodology is developed. To this end, we present a novel Pythagorean fuzzy combined compromise solution (PF-CoCoSo) framework to rank the alternatives. In addition, we propose new Pythagorean fuzzy similarity measures to develop the weight-determining procedure for the criteria. In addition, a comparison with extant measures is presented to verify the effectiveness of the introduced similarity measures. To demonstrate the effectiveness and feasibility of the proposed framework, a case study of MWTT selection is presented. From the assessment, the autoclaving technology is the most suitable alternative among the MWTTs. Further, a sensitivity analysis and comparative study are performed to highlight the strength and validity of the introduced methodology.

Sequencing batch airlift reactors (SBAR): a suitable technology for treatment and valorization of mineral oil wastewaters towards lipids production

Produced water (PW) and spent oil-based wastewaters are some of the largest mineral oil wastewaters produced. Due to the high toxicity of hydrocarbons, several countries set stringent discharge limits and its treatment is compulsory before discharge. In this work, biological treatment of mineral oil wastewaters coupled with the production of bacterial lipids is demonstrated in sequential batch airlift reactors (SBAR). Two SBAR (2 L working volume) were used for treatment of PW and lubricant-based wastewater (LW), inoculated with Alcanivorax borkumensis SK2 (SBARAb+PW) and Rhodococcus opacus B4 (SBARR.o+LW), respectively. A total petroleum hydrocarbon removal (TPH) efficiency up to 96% and 80% were achieved for SBARAb+PW and SBARR.o+LW, respectively. Intracellular lipids production in SBARAb+PW increased when lower TPH/N ratios and higher feast stage duration were applied (up to 0.74 g g-1 cell dry weight (CDW)), whereas in SBARR.o+LW higher lipids production was observed for higher TPH/N ratios (0.94 g g-1 in CDW). Triacylglycerols (TAG) were the main intracellular lipid accumulated in both SBARAb+PW and SBARR.o+LW operations, while wax ester (WE) production was only observed extracellularly in the SBARAb+PW.

Selection of the Most Feasible Wastewater Treatment Technology in Pakistan Using Multi-Criteria Decision-Making (MCDM)

Industrialization plays an important role in the economic growth and development of a country. Pakistan is a developing country that heavily relies on its industrial sector to aid in its sustainable economic growth but the increase in the number of industries has also resulted in a rapid increase in pollution due to poor management of industrial effluents. Many technological solutions are available for wastewater treatment, ranging from conventional treatment methods to advanced technologies. However, the selection of an optimal wastewater treatment technology (WWTT) is a difficult task owing to several alternatives available and multiple criteria involved in the selection process. To resolve this issue, the purpose of this paper is to evaluate different WWTT based on certain pre-defined criteria, and selecting the most suitable technology using multi-criteria decision-making (MCDM) approach. In this research, five WWTT used in Pakistan were evaluated based on ten criteria using fuzzy VIKOR method. The results of the study show that activated sludge is the most suitable technology for industrial wastewater treatment in Pakistan being ranked first, followed by membrane filtration and sequential batch reactor ranked second and third respectively. The study provides an evaluation framework for decision-makers in Pakistan to select the most appropriate technology for wastewater treatment. The selected alternative can further be implemented in the existing and upcoming industrial estates to reduce the ever-increasing water pollution in Pakistan.

Advantages of using ohmic heating in Dulce de Leche manufacturing

Ohmic heating (OH, 0, 2, 4, 6, 8, or 10 V cm−1, 72 °C/15 s, 60 Hz) at Dulce de leche processing was investigated. The equipment consisted in an ohmic heating chamber, and rectangular 316 stainless steel electrodes positioned 10 cm apart. OH-treated milk resulted in improvements in the quality parameters of Dulce de leche, with a decrease in energy expenditure (69.85–141.86 vs 1260 kJ) and hydroxymethylfurfural (HMF) levels (7.64–8.54 vs 9.53 μmol L−1), an increase in product homogeneity, and formation of volatile compounds important for the sweetness of Dulce de leche (butanoic acid and 2-furan methanol). In addition, the physicochemical composition, fatty acid profile, and health indices (atherogenic, thrombogenic, desired fatty acids, and hypercholesterolemic saturated fatty acids) of the products remained without changes. In particular, the use of higher electric field (> 6 V cm−1) led to a 14–78% decrease in process time, and improved volatiles profile. OH has proven to be a suitable technology for milk treatment, resulting in improvements in the quality parameters of Dulce de leche with positive impact at the process time and energy expenditure. Industrial relevanceThe Dulce de Leche processing is characterized by long cooking times to acquire its typical characteristic color and flavor. Normally, it is used pasteurized milk as raw material. Ohmic heating decreased the total time of processing in Dulce de leche manufacturing, providing an economy at the in the energy costs without significant change at the quality parameters of the final product.

Development of a decision support system for the selection of wastewater treatment technologies

Multiple factors including technical, social, economic, regulatory, governmental, and environmental add complexity in the process of selecting a suitable wastewater treatment technology. To overcome this issue, this paper aims to propose a decision support system (DSS) for the selection of wastewater treatment technologies. The proposed system has been developed using a detailed review of the state-of-the-art in wastewater treatment, implemented using Microsoft Visual Studio 2010 and validated through real-time case studies. The system is categorized into four treatment levels based on wastewater complexity and the required degree of treatment. These include preliminary, primary, secondary, and tertiary treatment. Based on the identified treatment levels, the proposed system suggests using any physical, biological, chemical, or hybrid treatment process. The developed DSS will aid the selection of suitable wastewater treatment technology from a set of alternatives while keeping user constraints, conflicting requirements, and prevailing conditions under consideration. Moreover, the system is capable to customize the treatment assembly at the planning stage with minimized costs, eliminate mistakes at the planning and design stage, facilitate decision making by narrowing down the alternative solution as per user requirements and prevailing conditions, incorporate customer demand, and promote sustainable development.

Sewage Sludge Thermal Treatment Technology Selection by Utilizing the Analytical Hierarchy Process

Sewage sludge management has gained significance in the last several years, due to its nutrient and energy content. However, technology selection is one of the greater challenges because it is not possible to implement a technology that covers all the requirements of the considered environments. Consequently, this paper shows an example of the utilization of an analytical hierarchy process, as a decision-making tool in terms of technology selection, for sewage sludge management in Rijeka, Croatia. The criteria structuring and evaluation process with the description of several possible alternatives for thermal treatment technologies are defined within this research. For the case of Rijeka, the best and most suitable technology for sewage sludge treatment is gasification, which coincides with the results obtained from the analysis of the literature review. According to the results in this paper, the possibilities of the use of this scientific method on the national level for the selection of sewage sludge treatment technology should be considered, due to the simplicity of its use and capability of its adaptation to various situations and areas.

Plasma Technology to Recondition Radioactive Waste: Tests with Simulated Bitumen and Concrete in a Plasma Test Facility

The operation and maintenance of nuclear power plants, the non-nuclear fuel cycle, etc generate low-level radioactive waste which, along with the historical radioactive waste from past nuclear activities, needs to be treated and stored, awaiting final disposal. Plasma technology offers a very effective way of treating this waste with a high-volume reduction factor (VRF), free from organics, liquids and moisture, and meets without a doubt the acceptance criteria for safe storage and disposal. By means of a plasma beam of approximately 5000°C, the inorganic materials are melted into a glassy slag, containing most of the radioactive isotopes while the organic material is gasified, oxidized and purified in an off-gas cleaning system. First the paper describes the new full-scale Plasma Melting Facility (PMF) at the Kozloduy Nuclear Power Plant in Bulgaria which was taken into nuclear operation in May 2018. The plant has a capacity of 250 tons per year and the maximum contact dose rates of the incoming waste is 2mSv/h. Different mixtures of radioactive waste packed in 200l drums were successfully treated resulting in a glassy slag free from liquids and organic material with an important volume reduction factor (VRF). The Project was co-financed through a grant by Kozloduy International Decommissiong fund (KIDSF) administated by the EBRD through Bulgarian national funding. Plasma is a suitable technology for treatment of problematic waste or even reconditioning waste so Belgoprocess was contracted to do plasma tests with simulated conditioned waste types. One can do tests on a laboratory scale on smaller samples and torch capacities of e.g. 50kW but Belgoprocess wanted to do more realistic and reliable tests. So Belgoprocess contracted Phoenix Solutions Co who has a full-scope test facility equipped with a 1200kW plasma torch for full-scope treatment of simulated conditioned waste. For a first confidential contract simulated 2001 (55 gallon) bitumen drums were treated. The drums contained different pucks of compacted waste such as rags, used filters, granulates, etc. The pucks were stacked in the 2001 drums and subsequently embedded with bitumen. A total of 6 drums were treated in the plasma facility. For a second contract simulated homogeneous 2001 (55 gallon) concrete drums with on the one hand concentrates and on the other hand spent resins were selected. A total of 6 drums with concrete and spent resins were treated and melted in the plasma testing facility. The paper describes the test facility, volume reduction factor (VRF) of different waste streams and most important parameters.

A model-based optimization study on greywater reuse as an alternative urban water resource

Integrated urban water management (IUWM) aims to promote water supply not only from conventional sources but also from wastewater reuse in part to address issues such as water scarcity. In line with the situation, this work concerns greywater reuse in synthesizing and retrofitting water network at household and community levels. We consider various water-using activities and suitable wastewater treatment technologies through a nonlinear optimization model based on a superstructure which incorporates multiple alternatives for greywater reuse, regeneration (treatment), and recycle. The model objective aims to minimize freshwater consumption and/or wastewater generation in addition to the fixed capital cost of installing the pipes and the variable operating cost of water pumping. The optimization procedure is carried out subject to complying with constraints to reduce the contamination level to acceptable reuse limits or otherwise for disposal or discharge to the environment while meeting various real-world design and operating specifications that include requirements for minimum water service and hygienic reasons. A real-world case study is illustrated on a residential household with four occupants by combining engineering experience and physical insights to obtain a realistic model representation of the problem. To circumvent the solution challenge presented by the nonconvex formulation, we apply a convexification strategy to handle the concave terms in the objective function. The proposed approach has demonstrated that significant reductions in freshwater use are possible.

Adoption of Circular Economy for A Sustainable Solid Waste Management System in Malaysia

The purposes of this study are to address the current solid waste management (SWM) issues and to evaluate the best available practices that can be adopted to develop a holistic, integrated, effective and a sustainable SWM system in Malaysia. The idea is to analyze and to evaluate the weaknesses of the current practice of “extract-make-use-dispose” linear economic (LE) model that causes depletion of natural resources, massive increase in the generation of solid waste, severe degradation of the environment and a substantial cost to manage. These results will be synthesized to establish critical gaps to benchmark against the new economic model of a circular economy (CE) that works on a closed-loop system of reducing, reuse and recycle (3R). CE aims to efficiently utilize the resources to allow for maximum reuse through refurbishment, remanufacturing and recycling which will minimize the wastages for disposal. This study employs a literature review to identify relevant practices of a circular business model that can potentially be adopted, a life-cycle (LC) analysis to assess the environmental impacts and a study on waste characteristic and its composition to determine the waste fraction and the amount of energy contained in the solid waste. This paper gives an insight into the possibility of embracing the concept of a CE alongside with a suitable treatment and disposal technologies to develop a sustainable SWM system in Malaysia. This holistic approach would able to minimize the waste through waste prevention, to maximize the economic return through reuse, recycle and recovery, to give the protection to the environment and to improve the quality of life.

Waste water treatment process using Nano TiO2

Textile industry outlet Waste water contain a several mixture of polluting substances involving solvents, detergents and dyes. Textile manufacturers are in a situation to sort out this issue by adopting a suitable treatment technology for textile effluent. Notably the application of ceramic Nano Filtration (NF) plays a significant role in recycling the specific waste in the textile industry thereby paving way to waste recycling instead of being disposed of in land whereas it seems to be impossible for most of the conventional technologies in treating this textile effluents. The Initial performances of commercial NF membranes have been studied thoroughly pertaining to Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) rejection. The outcome showed that maximum separation of dye and salts where achieved by some of the commercial membranes while some achieved higher flux owing to the inconsistent parameters of textile waste water and NF membranes chosen. These work forefronts and studied the problem associated with textile waste water and waste water recycling using the ceramic nano filtration membrane.

Hydrogen Production from Makgeolli Wastewater Using a Single‐Chamber Microbial Electrolysis Cell

Domestic and industrial wastewaters are subject to the biological treatment process before discharged to environment. In that process, organic substances contained in the wastewater are degraded by microorganisms. Microbial electrolysis cells (MECs) are suitable technology for wastewater treatment, simultaneously producing hydrogen. In most case, however, a significant amount of methane instead of hydrogen is produced when the wastewater is used for MECs. Here we show that hydrogen is the main product when Makgeolli wastewater (MW) is used as a substrate in a single‐chamber MEC which was operated using acetate and MW. Although current generation profiles vary according to the substrate type and the applied voltage, hydrogen portions were maintained over 90% at −0.6 V and −0.8 V with production rates of 0.95 and 1.55 m3H2/m3/d, respectively. This result shows a possibility of implementing MECs in the real wastewater treatment and hydrogen production.

The Self-Forming Dynamic Membrane BioReactor (SFD MBR) as a suitable technology for agro-industrial wastewater treatment

Two bench-scale Self-Forming Dynamic Membrane BioReactors (SFD MBR), equipped with 50 μm nylon meshes were set up and operated under aerobic conditions in order to treat canning and winery wastewaters. The results showed different behaviors of the two systems, confirming the strong dependence of SFD MBR performance on the type of biomass and, in turn, on the type of stream being treated. Both plants achieved good results in terms of effluent quality, demonstrating the suitability of the proposed technology. Median values of effluent turbidity were 2.7 and 15.4 NTU (Nephelometric Turbidity Units) in the reactors fed with canning wastewater and winery wastewater, respectively. The removal of organic matter (as COD, Chemical Oxygen Demand) was consistently above 90 %, although the retention of suspended solids was variable and somewhat dependent on operating conditions and feed composition. The activated sludge characteristics were observed to affect filtration performance and in particular the capillary suction time (CST) was a possible indicator of efficiency, with a threshold value of 11 s above which filtration performance decreased. This parameter is proposed as an early warning tool for changes in the filtration performance of an SFD MBR, both for effluent quality and cleaning requirements.

Spatial and seasonal variation of lake water quality: Beseka in the Rift Valley of Oromia region, Ethiopia

Nowadays, freshwater pollution is an environmental crisis caused mainly by anthropogenic activities. The water quality deterioration of Lake Beseka which is located in the Ethiopian portion of the East African Rift Valley is associated with rapid expansion of that lake that is not fully understood yet. This water quality impairment is the major cause of severe shortage of water supply for human consumption, irrigation use, and public health problems in that area. Hence, this study aimed to investigate the physicochemical and metal concentrations of Lake Beseka and evaluate the impact of the spatio-temporal variation on the water quality. Water samples were collected from six sampling sites during the dry and wet seasons. The concentration ranges for physicochemical parameters evaluated were: temperature (25–40 °C), electrical conductivity (EC) (1407–3321 μs/cm), turbidity (28.5–63.0 NTU), total dissolved solids (TDS) (740–1598 mg/L), pH (7.47–10.86), NO3−–N (0.30–16.69 mg/L), PO43−–P (0.03–13.00 mg/L), SO42− (10.00–70.00 mg/L), Cl− (0.00–200.00 mg/L), F− (0.40–3.80 mg/L), K (0.30–2.40 mg/L), Mg (0.40–2.46 mg/L), Ca (0.40–3.80 mg/L) and Fe (0.40–3.80 mg/L). For several parameters investigated, the result showed some significant differences (p < 0.05) among the six water samples during both the rainy and dry seasons, except for turbidity, EC, NO3−–N, PO43−–P, SO42− and Cl−. The values of many water quality parameters exceeded the WHO water quality guidelines for drinking water. Furthermore, the water is not suitable for irrigation due to extremely high values of pH (10) and other parameters dominating in salt lakes. This deteriorated water body has the potential to interfere with the natural function of the ecosystem by affecting human health in the area. Hence, to upgrade water quality to meet public health and environmental safety, implementation of suitable water treatment technologies is a crucial agenda to use Beseka lake water.