Maximum Chemical Oxygen Demand Research Articles

Mathematical approach towards non-stepwise performance assessment in HUASB reactor for wastewater treatment from pulp and paper mills

A lab-scale Hybrid Upflow Anaerobic Sludge Blanket (HUASB) reactor with a working volume of 6.5 litres has been taken for the performance analysis, in the treatability study of pulp and paper mill wastewater. In order to analyze the performance of the reactor, operational parameter like hydraulic retention time (HRT) was varied from 10, 20, 30 and 40 h. In addition to that, performance parameters like chemical oxygen demand (COD), pH, volatile fatty acids (VFA), alkalinity, gas production and VFA/alkalinity ratio are analyzed to check the reactor efficacy. The maximum COD removal efficiency of 81.3% is obtained at 40 h HRT, with gas production (methane content of 58%). Also, the obtained results are fitted to the kinetic models like the standard first order, first order and second order to evaluate the performance of the HUASB reactor.

Biosynthesized α-MnO2-based polyaniline binary composite as efficient bioanode catalyst for high-performance microbial fuel cell

Microbial fuel cell (MFC) has novel technological advances in simultaneous power generation and wastewater treatment applications. In this study, low-cost biosynthesized α-MnO2 nanoparticles integration with conducting polyaniline (PANI) matrix to form α-MnO2/PANI hybrid nanocomposite was fabricated by in situ polymerization method. The prepared material was characterized through UV-Vis spectroscopy, XRD, FTIR, TGA-DTA, DSC, SEM, cyclic voltammetry, and impedance spectroscopy. MFC performance study was done by using an external resistance in the range of 100 Ω–100 kΩ. The continuous test on bare pencil graphite electrode (PGE), α-MnO2/PGE, PANI/PGE, and α-MnO2/PANI/PGE were evaluated in glucose-fed-Escherichia coli-based MFC. It was found that α-MnO2/PANI/PGE produces a maximum power and current densities of 426.26 ± 38.89 mW m−2 and 2485.51 ± 397.31 mA m−2, respectively. This was 6.5 and 5.7-fold higher in power and current densities than unmodified PGE. The maximum chemical oxygen demand produced by hybrid composite modified anode during closed circuit voltage or with external resistance and open circuit voltage (OCV) (circuit without connecting external resistance) measurements were found to be 88.19% and 92.27%, respectively. A maximum of 650.61 ± 10.11 mV OCV was obtained by α-MnO2/PANI/PGE while 222.36 ± 8.16 mV of OCV was generated by PGE.

An integrated approach of adsorption and membrane separation for treatment of sewage water and resource recovery

The traditional sewage treatment methods are facing several challenges and barriers necessitating the development of newer treatment approaches along with value addition and resource recovery. The present work demonstrates the integration of Carbon Capture Reactor (CCR) i.e. adsorption column and membrane separation for efficient treatment of wastewater collected from different sewage sources with resource recovery in terms of CCR-Oil which is a mixture of organic compounds having calorific value of 18−20 MJ/Kg. Detailed physicochemical characterization of sewage water was conducted for quantification of chemical oxygen demand (COD), total dissolved solids (TDS), and conductivity. The obtained CCR-Oil was also tested for its physicochemical properties by using attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), gas chromatography–mass spectroscopy (GC–MS), and elemental and calorific value analysis. In the adsorption studies, various hydrophobic, hydrophilic and ion exchange resins were tested for maximum COD reduction. Hydrophobic resin showed excellent performance with 50.0 ± 0.4 % COD reduction and maximum dynamic binding capacity of 0.0208 mg/L. The continuous CCR operation showed a 45.5 ± 1.5 % COD reduction with 1.5 bed volume (BV) per hour flow rate for up to 320 bed volume loading of sewage water. The integration of CCR with the reverse osmosis (RO) membrane showed an overall 85.0 ± 2.5 % COD reduction and 93.0 ± 0.5 % TDS reduction with the maximum flux of 34 L/hr/m2 (LMH) and no sign of membrane fouling, indicating very good performance for the combination approach. It was clearly demonstrated that the hybrid approach of adsorption followed by membrane separation provides a sustainable, efficient and economic alternative for the treatment of sewage water also yielding the benefits of resource recovery.

Lastik Üretiminden Kaynaklanan Sürfaktan İçeren Atık Suların Koagülasyon Bazlı Arıtma Alternatiflerinin PROMETHEE Yaklaşımı ile Değerlendirilmesi

In this study, the treatment of wastewater containing surfactant used to prevent the sticking of the raw material pulp pressed in the tire production process, with conventional coagulation and microwave oxidation-supported electrocoagulation processes was investigated. The processes were optimized to ensure maximum chemical oxygen demand removal by the Taguchi experimental design method (L8). With Pareto analysis, it was found that the most effective parameter in microwave oxidation-supported electrocoagulation processes is microwave duration while the most effective parameter in the conventional coagulation process was FeCl3.7H2O dose. Analysis of variance found that the models determined for both processes were significant in explaining chemical oxygen demand removal. The appropriate process has been determined as the microwave oxidation-supported electrocoagulation, with the PROMETHEE method considering the optimum experimental conditions, chemical oxygen demand removal, chemical sludge production, operating cost and the preferability criteria of the processes. In microwave oxidation-supported electrocoagulation process, under optimum conditions, chemical oxygen demand removal efficiency, the amount of sludge production and operating costs were found as 66.9 %, 6.27 g / L and 1.195 € / L, respectively. It was determined that the criteria of chemical oxygen demand removal efficiency and sludge amount had a positive effect on the selection of the process.

Green ZnO nanoparticles photocatalyst for efficient BR51 degradation: Kinetics and mechanism study

AbstractDyes are broadly utilized and therefore wastewaters discharged into rivers or public sewage treatment plants are extremely polluted. Thus, the current work aimed to study the kinetic for photocatalytic degradation of Basic Red 51 (BR51) dye in aqueous solution by green synthesized zinc oxide nanoparticles (ZnO NPs). The results revealed that the maximum degradation (98.40%) and chemical oxygen demand (COD) removal (98.08%) was recorded with 150 mg of ZnO NPs, pH 3 and 5 ppm of BR51. ZnO NPs showed high reusability of 95.73%. The photocatalytic degradation of BR51 follows pseudo first‐order kinetics, the apparent rate constants (Kapp) of solar photocatalytic degradation of BR51 were determined as 0.3798, 0.6066, 0.2747 and 0.1307 min−1 for 5, 10, 15 and 20 ppm of BR51 at optimum condition respectively. Phytotoxicity study confirms that the degraded products of BR51 are non‐toxic. This confers the possibility of applying green ZnO NPs for the treatment of industrial wastewaters containing dye pollutants to ensure the environmental sanitation for future generations.

Photo-Fenton process for removal of polycyclic aromatic hydrocarbons from hazardous waste landfill leachate

Polycyclic aromatic hydrocarbons (PAHs) are the toxic and persistent micro-pollutants recalcitrant to biodegradation. Photo-Fenton process is a commonly adopted advanced oxidation process. Advanced oxidation processes generate highly reactive hydroxyl radicals (OH·) which completely mineralise the organic contaminants. This study aims to find the efficiency of photo-Fenton oxidation process in the removal of PAHs and COD from landfill leachate, and investigate its effect on 16 PAHs according to their number of aromatic rings. Experiments were designed using central composite design, a module of response surface methodology (RSM) in the Design-Expert software. pH, Fe2+ concentration, H2O2 concentration, reaction time and UV intensity were the five experimental variables which were optimised and modeled successfully. The statistical analysis proved that all the variables have significant effect on the model. The value of R2 (0.94) showed a high reliability in the estimation of chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency. Optimum experimental conditions of pH 6.5, Fe2+ 1.1 g/L, H2O2 concentration 5.5 g/L, reaction time 40 min and UV intensity 13.5 W resulted in the maximum chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency of 84.43% and 92.54%, respectively. Validation was carried out by conducting additional set of experiments, and the small gap between observed and predicted values confirmed that central composite design is the effective tool to optimise the photo-Fenton oxidation process in the degradation of chemical oxygen demand and polycyclic aromatic hydrocarbons.

Treatment of gray wastewater and heavy metal removal from aqueous medium using hydrogels based on novel crosslinkers

AbstractWater contamination by heavy metals is a serious environmental problem. Several adsorbents with high adsorption capacity have been reported by researchers. In this paper we report the application of a new crosslinker allyl sorbitol (AS), and two other crosslinkers viz. allyl mannitol (AM) and allyl pentaerythritol (AP), toward the synthesis of polymer hydrogels. These hydrogels have been utilized for the removal of heavy metal ions from water. Chemically crosslinked polyacrylic acid hydrogels have been prepared using these crosslinkers viz. AS or AM or AP. The synthesized crosslinked hydrogels have been utilized for the removal of heavy metal ions from water. The maximum copper (Cu) metal ion removal of 81.8, 81.6, 86.8% and adsorption capacity of 409, 408, 434 mg/g were found with AS, AM and AP crosslinker based hydrogels respectively. While the maximum nickel (Ni) metal ion removal of 96.8, 96.6, 99.0% and adsorption capacity of 484, 483, 495 mg/g were found with AS, AM and AP crosslinkers based hydrogels respectively. The maximum chemical oxygen demand (COD) reduction of 72, 74, 78% and total dissolved solids reduction of 86%, 83%, 95% were found with AS, AM, AP based polymer gel respectively. Approximately, 439.2, 451.4, and 475.8 (mg COD removed/g polymer gel) of pollutants reduction capacity was achieved during their treatment.

Investigation of flow dynamic characteristics of inverse fluidized bed biofilm reactor for degrading pharmaceutical based biomedical wastewater

The paper investigates the flow dynamic behaviour of inverse fluidized bed biofilm reactor (IFBBR) for the treatment of pharmaceutical based biomedical wastewater. The residence time distribution (RTD) study has been employed as a tool to investigate the flow dynamic behaviour of wastewater within the reactor. The biofilm reactor is operated using Pseudomonas fluorescens for various ratios of settled bed volume to reactor working volume (Vb/Vr) with different superficial air velocities and examined their impact on flow dynamics. The outcomes of this study demonstrate the presence of dead volume and short circuiting in the reactor were reduced for the optimized (Vb/Vr) ratio of 0.20 and optimum superficial air velocity (Ug)m of 0.220 m/s. The potential of IFBBR was experimentally validated by analysing the chemical oxygen demand (COD) removal efficiency, total dissolved solids (TDS) and total suspended solids (TSS) emanating from the wastewater. Findings of this study reveals that maximum COD reduction of about 92% was achieved when the reactor was operated with (Vb/Vr)m of 0.20 with superficial air velocity, Ugm of 0.220 m/s showing the optimal operating parameters for IFBBR which has good mixing and less back mixing condition inside the reactor.

Utilization of Alyssum mucilage as a natural coagulant in oily-saline wastewater treatment

Wastewater treatment with natural coagulants is an area that is well-researched and covered in the literature, but new research in this current and ongoing field is still interesting. The present analysis was conducted as the first study to investigate the use of Alyssum mucilage as a new, natural, and cost-effective coagulant for the treatment of synthesized bilge water. To the best of the authors’ knowledge, no previous study has specifically devoted to implementing a systematic analysis of a new coagulant (Alyssum mucilage) within the framework of central composite design-response surface methodology (CCD-RSM), adaptive neuro-fuzzy inference system (ANFIS), and artificial neural network (ANN). Thus, to spot the lights over the mentioned gaps, the current study was undertaken as the first attempt to perform highly comprehensive mathematical, kinetic, and statistical analyses for a quantitative definition of the coagulation-flocculation process of oily-saline wastewater treatment using Alyssum mucilage. In this study, three process-related parameters, such as coagulant dose, contact time, and pH, were introduced for modeling, optimization, and cost analysis of the investigated application. At the optimum conditions (coagulant dose = 40.5 mg/L, pH = 7.05, and contact time = 34.9 min) of Alyssum mucilage, the maximum chemical oxygen demand (COD), turbidity (TU), and surfactant removal efficiencies were obtained as 84.63 %, 96.25 %, and 99 %, respectively. Under the optimum conditions (coagulant dose = 301.8 mg/L, pH = 6.53, and contact time = 23.1 min) of poly aluminum chloride (PAC), used as a comparative polymerized metal coagulant, the maximum COD, TU, and surfactant removal efficiencies were determined as 92.30 %, 99.92 %, and 99 %, respectively. Compared to CCD-RSM, ANFIS and ANN showed high accuracy with R2 values more than 0.990 for both PAC and Alyssum mucilage. The kinetic study revealed that the second-order model performance was superior to the first-order model. Fourier-transform infrared spectroscopy (FTIR) analysis of Alyssum mucilage demonstrated that the functional groups presented in the composition of this coagulant caused coagulation and bonding between the particles. Furthermore, the zeta potentials of bilge water, coagulant, and treated bilge water indicated that the possible mechanism of the coagulation would be adsorption and bridging.

Treatability of household waste plastic garbage bag recycling industry wastewater with membrane

In this study, household waste plastic garbage bag recycling industry wastewater was treated by a membrane process to recycle water for using in the bags washing process. Two different ultrafiltration (UP150 and UP005) and nanofiltration (NF270 and NF90) membranes were tested. The steady-state permeate flux was obtained 14.9 and 19.2 L/m2.h at 5 bar for UP150 and UP005 membranes, respectively. However, the steady-state permeate flux was 12.9 and 8.9 L/m2.h at 20 bar for NF270 and NF90 membranes, respectively. The chemical oxygen demand (COD) was also tested for all membrane permeates and the highest COD removal efficiency was obtained for NF90 membrane. Thus, optimization was carried out using NF90 membrane and the effect of transmembrane pressure (10, 20, 30 bar) and solution pH (5, 7, 9) on COD removal efficiency was tested. The results showed that the highest steady-state permeate flux (23.5 L/m2.h) and COD removal efficiency (95.1%) were obtained at 30 bar and pH 9. After the optimization of the membrane type and operating conditions, 75% recovery was obtained to re-use in the bags washing process. The concentrate stream was treated by an activated sludge process to manage membrane concentrate and to provide discharge standards. The maximum COD removal efficiency in biological treatment for membrane concentrate stream was 96.2% under steady-state condition using a sequencing batch reactor (SBR) operated at 10 days of sludge retention time and 12 h of hydraulic retention time. The proposed combined process including membrane and activated sludge processes was successfully used to recover wastewater.

Removal of Basic Brown 16 from Aqueous Solution Using Durian Shell Adsorbent, Optimisation and Techno-Economic Analysis

Azo dyes including C. I. Basic Brown 16 (BB16) are one of the coloured organic compounds that have adverse effects on human health and the environment. The current work aims to optimise the adsorption of C.I BB16 in aqueous solution using durian (Durio zibethinus murray) shell as a low-cost green adsorbent. Durian shell was characterised by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The adsorption process was optimised with response surface methodology (RSM) based on pH (4–8), time (30–240 min), durian shell dosage (0.1–1.0 g/L) and initial concentration of C.I BB16 (10–20 ppm). The removal efficiency was determined based on the reduction of chemical oxygen demand (COD) and the decolourisation of C.I BB16. The techno-economic analysis was described in the current work to know the economic feasibility of durian shells as an adsorbent. The SEM images showed that durian shell adsorbent has a smooth surface with no pores. FTIR spectra confirmed the presence of -C-O, =C–H, C=C, -C-O-C and O-H bonds in durian shell. Maximum decolourisation (77.6%) and COD removal (80.6%) for C.I BB16 was achieved with the interaction between pH, time and adsorbent dose and initial concentration of C.I BB16. The optimal operating factors for adsorption of C.I BB16 recorded at pH 8, time (30 min), durian shell dosage (1 g/L) and 15 mg /L of C.I BB16 concentrations were 77.61 vs. 74.26 (%) of C.I BB16 removal and 80.60 vs. 78.72 (%) of COD removal with an R2 coefficient of 0.94 at p < 0.05. The specific cost of durian shell coagulant production is USD 172.71 per ton which is lower than the market price of honeydew peels-activated carbon (HDP-AC) (USD 261.81) and the commercial market price of activated carbon which is USD 1000.00/tons. These findings indicated that the durian adsorbent provides alternative methods for treating hair dye wastewater. These findings indicated that durian shells have a high potential for the adsorption of C.I BB16 in aqueous solution.

Anaerobic co-digestion of landfill leachate and acid mine drainage using up-flow anaerobic sludge blanket reactor.

A laboratory-scale up-flow anaerobic sludge blanket (UASB) reactor was developed and constructed for the treatment of landfill leachate and acid mine drainage (AMD). The removal of chemical oxygen demand (COD), sulfate, and metal ions was studied. The maximum COD and sulfate removal efficiency reached 75% and 69%, respectively, during the start-up phase of the UASB. The hydraulic retention time (HRT) had a significant influence on the system. The maximum removal efficiency for COD and sulfate reached 83% and 78%, respectively, at an HRT of 20 h. The methane production process competed with the sulfate reduction process in the UASB. The fractionation of metals in the sludge was analyzed to facilitate metal recovery in a later processing stage. The most abundant sulfate-reducing bacteria was Desulfobulbus, and the methanogen archaeal community in the reactor was mainly composed of Methanobacterium.

Combined oxidation processes based on ultrasound, hydrodynamic cavitation and chemical oxidants for treatment of real industrial wastewater from cellulosic fiber manufacturing sector

The present work reports the application of cavitation for the real industrial effluent treatment, which was derived from the cellulosic fiber manufacturing sector, individually or in combination with advanced oxidation processes. Cavitation has been applied with the objective of reducing the chemical oxygen demand (COD) of the industrial effluent and to study its simultaneous effect on the total dissolved solids (TDS). A combination of cavitation with different additives/oxidants viz. hydrogen peroxide (H2O2), ozone (O3), sodium hypochlorite (NaCLO), and Fenton's reagent have been studied. Ultrasonic horn operating at an acoustic power of 120 W with a frequency of 20 kHz and duty cycle of 80% (8 sec ON, 2 sec OFF) was used for treatment based on ultrasound. Under optimized conditions, it was established that a combination of ultrasound (US) with Fenton’s reagent using an optimum mole ratio of H2O2/Fe2+ of 3 followed by lime coagulation gave a maximum COD reduction of 92% and also resulted in TDS reduction of 31%. Studies were also performed using a hydrodynamic cavitation (HC) reactor (10 L capacity) where slit venturi was used as a cavitating device. It has been observed that a combination of HC with Fenton's reagent at molar ratio of H2O2/Fe2+ as 3 gave the maximum COD reduction of 86% and a TDS reduction of 47%. It was also established that lime treatment played an important role in separating the sludge formed during the Fenton oxidation treatment and in converting brownish colored effluent to colorless effluent. Overall, it has been established that cavitation coupled with the Fenton oxidation was most the efficient among all studied combinations giving a good COD reduction as well as TDS reduction with a final colourless nature of effluent.

Treatment of wood industry wastewater by combined coagulation-flocculation-decantation and fenton process.

In the present research, the efficiency of turbidity and chemical oxygen demand (COD) reduction from the wood industry wastewater (WIW) by the use of a combined coagulation-flocculation-decantation (CFD) - Fenton process was studied. Firstly, the performance of three coagulants such as ferric chloride (FeCl3 ), aluminum sulphate (alum), and polyaluminum chloride (PACl) was evaluated. The polyacrylamide (PAM) was used as a flocculant. The results showed that the polyaluminum chloride had a high removal efficiency. The COD reduction of 84.1% and turbidity removal of 82.0% of were obtained in coagulation-flocculation-decantation (CFD). Secondly, Fenton process was optimized, by the use of a response surface methodology (RSM), with application of a central composite design (CCD). The maximum turbidity and COD removal obtained by this process were 94.1% and 72.5% respectively, under optimal conditions ([Fe2+ ]=250mg/L, [H2 O2 ]=500mg/L, pH 3.5, time 60min). The kinetics of COD and turbidity removal were determined by the model of first order. In conclusion, the combination of coagulation-flocculation-decantation (CFD) - Fenton process presented as a remarkable method for wood wastewater treatment. PRACTITIONER POINTS: A combination of coagulation-flocculation-decantation and Fenton process was introduced for the wood industry wastewater treatment. A designed experimental approach for treatment of wood industry wastewater using a Fenton process was studied. The yields of COD, BOD5 , N-NO3 , P-PO4 , and dye removal were obtained according to the standard limits in Iran.

Flow shear stress applied in self-buffered microbial fuel cells

The development of renewable and clean energy has been the priority of the global research field due to the urgent effects of climate change. Microbial fuel cell (MFC) is recognized as a sustainable approach to simultaneously generate power and treat wastewater through the employment of microorganisms as catalyst. The use of buffer solution in the wastewater treatment makes the commercial application of MFCs challenging due to their environmental impact and high costs. This work uses rotational motion to generate the flow stress in the anode chamber of the MFCs to enhance biofilm growth and mass transfer that leads to an overall performance improvement of the system. The effects on pH, chemical oxygen demand (COD), and power density were evaluated under rotational speeds of the magnetic stirrer from 0 to 640 rpm. The influence of the stirrer was then assessed utilizing the same parameters specified for scenarios with and without buffer. The results reveal that at 480 rpm of stirring speed, the pH value was neutral with a maximum COD removal of 82 % for bufferless and 93 % for buffered scenarios. In addition, for bufferless operation at 480 rpm yielded a power density of 402 mWm−2. The results of the flow stress analysis for bufferless and buffered MFCs are beneficial for the commercialization and future development of the system for wastewater treatment applications.

Optimization and Mechanism Study on Destruction of the Simulated Waste Ion-Exchange Resin from the Nuclear Industry in Supercritical Water

The optimization and mechanism for oxidation of the waste anion exchange resin from the nuclear industry in supercritical water were investigated. To achieve the maximum chemical oxygen demand (COD...

Batch electrochemical coagulation of real textile wastewater using Cu-SS and SS-Cu electrode combinations and its settleability aspects

Copper and stainless steel electrodes were used in batch electrochemical coagulation (BECC) for the treatment of real textile wastewater using 16 electrode combinations. Out of 16 Cu-SS and SS-Cu combinations (eight combinations each), only 4SS and 3SS-1Cu electrodes operated at cell voltage of 18 V and current density of 180 A/m2 gave maximum color and chemical oxygen demand (COD) removals. The COD removal was observed to be 89.37% for 4SS and 72.34% for 3SS 1Cu electrodes from CODo 3,012 mg/L. Color removal was 97% and 98% from its initial value of 1,000 Pt-Co unit for 4SS and 3SS-1Cu combinations. Water quality parameters like total dissolved solids, chloride, nitrate, phosphate, and sulphate reduced from their initial values while using all 4SS and 3SS-1Cu electrode arrangements. Other control factors exercised for optimal operations were ECC floc settling pattern and sludge volume index (SVI). SVI values were found to be <100 mL/g for both electrode combinations.

Effect of Combining Different Substrates and Inoculum Sources on Bioelectricity Generation and COD Removal in a Two-Chambered Microbial FuelCell: A Preliminary Investigation

Abstract In recent years, fuel cells have become a renewable source of energy. Among different kinds of fuel cells, microbial fuel cells, which convert organic substrates to electricity by electrogenic bacteria have attracted most attention. In this study, which is preliminary in nature, potential of electricity generation and chemical oxygen demand (COD) removal were studied in a two-chamber microbial fuel cell (MFC) reactor. Effect of type of feedstock and inoculum source on bioelectricity generation and COD removal was studied as well. Brewery wastewater and potato waste were used as substrates while anaerobic sludge and cow dung were used as inoculum sources. The substrate and inoculum sources were in 8.2:1 ratio and a phosphate buffer was added to the anode compartment to regulate the pH. The system was operated at 30 °C and a home-made membrane served as a bridge between the electrodes. A maximum voltage of 3.6 mV was generated from the brewery wastewater sludge and the maximum COD removal after 3 days was 43.7 %. It was further found that the use of animal dung as inoculum source outperformed the use of sludge as regard the bioelectricity generation but not for COD removal. Similarly, the use of the brewery waste as an organic substrate outperformed the use of potato waste as regard the bioelectricity generation but not for COD removal. All experiments yielded a measurable voltage, however, the unsteady behaviour of the voltage output made it difficult to compare substrates in terms of their viability as organic fuel. Therefore, future studies should consider conducting substrate physico-chemical analysis and genomic analysis of the inoculum sources to understand their composition.

Biological treatment of organic compounds in produced water with use of halotolerant bacteria

Oilfield produced water (PW) is a mixture of different organic and inorganic compounds. The effects of discharging PW into the environment have lately become a major issue of environmental concern. This study aims to consider the capability of a gram-positive bacterium named Rhodococcus erythropolis PTCC 1767 in biological treatment of synthetic and real PWs. A stepwise adaptation strategy was applied for acclimation of the microorganism, by increasing chemical oxygen demand (COD) of the synthetic PW. The maximum COD removal efficiency was observed at 97% in PW with 600 mg/L COD. Also, by raising concentration of NaCl (up to 60 g/L), the stepwise adaptation strategy was performed for acclimated bacteria. The maximum COD removal efficiency occurred in the presence of 25 g/L NaCl. The results of total organic carbon (TOC) analysis revealed a removal efficiency of 85% and GC-MS analysis indicated a removal of 93% hydrocarbons (C14-C26). The adapted cells were then applied for treating the real PW in which a COD removal efficiency of 52% was achieved.

Integral Application of Chemical Mass Balance and Watershed Model to Estimate Point and Nonpoint Source Pollutant Loads in Data-Scarce Little Akaki River, Ethiopia

The quality of Little Akaki River in Addis Ababa (Ethiopia) is deteriorating significantly due to uncontrolled waste released from point and diffuse sources. In this study, pollution load from these sources was quantified by integrating chemical mass balance analysis (CMB) and the watershed model of pollution load (PLOAD) for chemical oxygen demand, biochemical oxygen demand, total dissolved solid, total nitrogen, nitrate, and phosphate. Water samples monitored bimonthly at 15 main channel monitoring stations and 11-point sources were used for estimation of pollutant load using FLUX32 software in which the flow from the soil and water assessment tool (SWAT) model calibration, measured instantaneous flow, and constituent concentration were used as input. The SWAT simulated the flow quite well with a coefficient of determination (R2) of 0.78 and 0.82 and Nash-Sutcliff (NSE) of 0.76 and 0.80 during calibration and validation, respectively. The uncharacterized nonpoint source load calculated by integrating CMB and PLOAD showed that the contribution of nonpoint source prevails at the middle and downstream segments of the river. Maximum chemical oxygen demand (COD) load from uncharacterized nonpoint sources was calculated at the monitoring station located below the confluence of two rivers (near German Square). On the other hand, high organic pollution load, biochemical oxygen demand (BOD) load, was calculated at a station upstream of Aba Samuel Lake, whereas annual maximum total dissolved solid (TDS), total nitrogen (TN), and phosphate load (PO4-P) from the nonpoint source in Little Akaki River (LAR) were found at a river section near Kality Bridge and maximum NOX load was calculated at station near German Square. The integration of the CMB and PLOAD model in this study revealed that the use of area-specific pollutant export coefficients would give relatively accurate results than the use of mean and median ECf values of each land use.