Organic Matter Removal Efficiency Research Articles

Co-digestion of two-phase olive-mill waste and cattle manure: Influence of solids content on process performance

The solids content is a key parameter in the development of anaerobic digestion as it can determine the proper operation and performance of the process. The influence of the total solids content on the mesophilic anaerobic co-digestion of two-phase olive-mill waste (2POMW) and cattle manure (CM) was investigated. Four different total solids (TS) concentrations, in a 75:25 mixture of 2POMW:CM, were studied in batch reactors of 2 L capacity: 10%TS (R10), 15%TS (R15), 20%TS (R20) and 28.6%TS (Reactor non-diluted). The methane yields and the organic matter removal efficiency for the reactor with 10 and 15% TS were significantly higher than in the reactors with a higher solids content (R20 and Rnd). The hydrolytic and acidogenic phases were not adversely affected by the total solid content since the concentration of volatile fatty acids (VFAs) increased as TS percentage increased. However, a clear effect on the methanogenic phase was observed, which led to the accumulation of VFAs in the reactors R15, R20 and Rnd. Experimental results have shown that the best conditions correspond to the reactor containing 10% TS. The volatile solids and VFA removal in reactor R10 were 57.5% and 93.7% respectively. Moreover, the methane yield and the specific methane production were 35.80 LCH4/kgVSadded and 82.51 LCH4/kgVSremoved respectively.

Study on removal of phosphorus and COD in wastewater by sinusoidal AC Fenton oxidation-coagulation

ABSTRACT In order to treat domestic wastewater containing phosphorus and chemical oxygen demand (COD), the new technology of Sinusoidal Alternating Current (AC) Fenton Oxidation-Coagulation (SACFOC) was used to improve the removal efficiency (Re ) and reduce energy consumption (EEC). The morphology, elemental composition, crystal structure and functional groups of the sludge were characterised by Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDS), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The results show that total phosphorus removal efficiency {Re (TP)} and removal efficiency of organic matter {Re (COD)} can reach 97.56% and 87.77%, respectively, but EEC is only 0.09 kWh·m−3 under the optimum conditions of pH0 = 3, current density (j) = 0.5 A·m−2, c 0(TP) = 18 mg·dm−3, c 0(COD) = 300 mg·dm−3, c 0(H2O2) = 0.06 mol·dm−3, t = 45 min. As compared with direct current (DC) Fenton Oxidation-Coagulation (DCFOC), the COD removal efficiency of SACFOC treatment was improved by 37%, but the energy consumption was reduced by 45%. The degradation process of total phosphorus and COD by SACFOC abides by the quasi-first-order kinetic model. The process of SACFOC includes double effects of electrocoagulation of iron sol by electrolysis and degrade COD by oxidation of formed hydroxyl radicals (·OH) in wastewater, which improves removal efficiency of total phosphorus and COD in wastewater. Our research findings will provide technical guidance and a theoretical basis for the simultaneous treatment of wastewater containing phosphorus and COD applying SACFOC process.

Characteristics of dissolved ozone flotation for the enhanced treatment of bio-treated drilling wastewater from a gas field

Working fluid preparation using treated drilling wastewater is of great potential for drilling wastewater reuse, especially in water-deficient and ecologically fragile areas, which require low levels of organic matter and suspended solids (SS). This study established the dissolved ozone flotation (DOF) process as the advanced treatment process to replace the original electrocatalytic system (ECS) which exhibited low organic and suspended solids removal efficiency. Higher and more stable organic matter, suspended solids and turbidity removal efficiency were obtained for the DOF process. Consequently, the lower fouling potential and higher water production rate of treated water from DOF process was observed for the following reverse osmosis (RO) system. In addition, brine drilling fluids can be successfully prepared using DOF effluent directly, which exhibited promising practical implications in the advanced drilling wastewater treatment. Based on organic matter fractionation and redundancy analysis (RDA), the hydrophobic acid (HOA), hydrophobic neutral (HON) and hydrophilic fraction (HI) contents significantly impacted brine drilling fluid preparation. Based on X-ray photoelectron spectroscopy (XPS) analysis, the aromatic carbon species in the HOA, HON and HI fractions were found to be the critical factors deteriorating the brine drilling fluid preparation. However, oxygen-containing groups played a positive role. The favorable brine drilling fluid preparation performance using DOF effluent directly can be ascribed to the removal of HOA, HON and HI fractions and enhanced generation of oxygen-containing groups in ozone flotation zone.

Evaluation of the Activation Procedure on Oxone Efficiency for Synthetic Olive Mill Wastewater Treatment

Wastewater from the olive oil industry is an environmental problem which is growing in the Mediterranean region. Presence of phenolic compounds and high organic matter load are characteristics of this effluent that make it difficult to treat. In this study, the applicability of sulfate radical based advanced oxidation processes (SRbAOPs), using peroxymonosulfate (PMS) as oxidant, was evaluated in the treatment of synthetic olive mill wastewater (OMW). Different procedures for PMS activation were studied such as activation by Fe(II), radiation (visible and UV-A) and ultrasounds. The operation conditions were optimized by testing pH values, Fe(II) and PMS loads. At optimal conditions ([PMS] = 1600 mg/L, [Fe2+] = 700 mg/L and pH = 5) 60 ± 2% COD removal was achieved. This process shows to be selective since complete degradation of 3,4,5-trimetoxybenzoic acid was obtained after 3 min of reaction. The addition of light, PMS/LED/Fe(II) and PMS/UV-A/Fe(II), did not increase the efficiency of organic matter removal, with 56 ± 2% and 58 ± 1% of COD removal, respectively, comparatively to PMS/Fe(II) (60 ± 2%). PMS activated by ultrasounds led to 52 ± 3% and 23 ± 2% removal of phenolic compounds and COD, respectively, after 60 min. Toxicity tests using Lepidium sativum showed that treatment with PMS/UV-A led to a treated sample with mild inhibition of plant growth.

Optimization of operational conditions and performances of pilot scale lumbrifiltration for real raw municipal wastewater treatment.

Lumbrifiltration (LF) has been promoted as a low-cost, low maintenance and efficient solution for domestic and municipal wastewater treatment especially. However, there have been limited studies investigating the optimal operating conditions and long-term performances of LF systems (especially in temperate climates). The key objectives of this study were to (i) to present an outcome of the operating conditions and associated performance of LF the systems studied in the literature regarding removal efficiencies for nutrients and organic matter (OM) in municipal and domestic wastewater (WW) treatment contexts, (ii) to generate long term and reliable results on the potential performances of LF systems for the treatment of real municipal WW (for both OM and nutrients), (iii) to optimize operational conditions such as active layer height, earthworms density, HLR and earthworms type, conditions for which it is still unclear from the current literature which are optimal, and (iv) to assess the performances of the LF in a "temperate climate" context. Overall, LF systems showed high removal efficiencies for organic matter and nutrients for all the operating conditions tested. The study also confirmed the positive impact of earthworms in achieving high level of nitrification of ammonium after a short start-up period. The system operation and performances were maintained without maintenance for the whole duration of the study (over 250days), showing the potential for keeping high level of performances for long-term periods. Recommendations are given in relation to LF system design such as optimal active layer height and hydraulic loading rate. The study also demonstrated the applicability and potential of Dendrobaena veneta as an alternative to Eisenia fetida (the latter generally being used in previous studies but are less available in some areas of Europe) for application in municipal wastewater treatment by LF.

Enhanced degradation and biogas production of waste activated sludge by a high-solid anaerobic membrane bioreactor together with in pipe thermal pretreatment process

An integrated system combining in pipe thermal pretreatment with a high-solid anaerobic membrane bioreactor (AnMBR) was developed to promote the anaerobic digestion of waste activated sludge (WAS). Two different pretreatment methods investigated were the venturi nozzle treatment (VNT) and steam injector treatment (SIT), both at a low temperature of 70 °C. The biogas production after pretreatment was 23.5–30.5% higher than that of untreated WAS, and the VS based biogas yield was 0.46–0.47 L/g-VS when HRT was 15 days. The membrane operated smoothly when the average flux was 9.6 and 4.5 L/m2/h under an MLTS of 25 and 30 g/L, respectively. The calculations of the mass balance indicated that 44–45% COD was converted to methane with pretreatment and only 1% remained in the permeate. That is, high energy recovery and organic matter removal efficiency were achieved for the treatment of WAS using the high-solid AnMBR with in pipe thermal pretreatment.

An eco-friendly approach for NaCl recovery from organic pollutants-containing waste salt by roasting together with low-grade pyrolusite

A large amount of organic pollutants-containing waste salt is produced in chemical production process, which is usually filled or deposited without treatment, causing serious environmental pollution and a waste of salt resource. In this work, in order to reduce the emission of toxic and harmful gasses and make full use of the organic matter component in waste salt, pyrolusite was used as an absorbent in the process of high-temperature pyrolysis of waste salt, of which MnO 2 was reduced to MnO while absorbing harmful gasses. The dual effects of roasting to remove organic pollutants from the waste salt and increase manganese leaching efficiency were systematically investigated, and the roasting mechanism and process were explored. Co-recovery of NaCl from organic pollutants-containing waste salt and manganese from pyrolusite ore was achieved. The results indicated that the optimum the removal efficiency of organic matter in the waste salt could be reached 99.45%, the purity of recovered NaCl products was 99.83% and leaching efficiency of 99.62% for manganese under the mass ratio of waste salt to pyrolusite of 8:5, the co-roasting temperature of 650 °C, and the roasting time of 40 min. • Co-recovery of NaCl from waste salt and Mn from low-grade pyrolusite was realized. • Pyrolusite was used as an adsorbent to absorb toxic gasses reducing pollution. • The mechanism and process of co-recovery were investigated.

Influence of water quality parameters on the removal of triclosan and ibuprofen in vertical subsurface flow constructed wetlands using multivariate analysis

The main objective of this study was to apply multivariate analysis, such as principal component analysis (PCA), to determine the influence of water quality parameters on the removal of triclosan (TCS) and ibuprofen (IB) in vertical subsurface flow constructed wetlands (VSSFs). For this purpose, two VSSFs were operated under TCS and IB concentrations of 10 μg/L. One VSSF system was planted with Agapanthus africanus and the other was left unplanted and used as a control. To determine the influence of water quality parameters on TCS and IB removal, the removal efficiencies for TCS, IB, organic matter and nutrients in VSSF systems were determined. Using these data, PCA was performed. The TCS and IB removal efficiencies in VSSF systems were found to vary between 60%–85% and 50%–84%, respectively. Regarding the effects of water quality parameters on TCS and IB removal, PCA showed that TCS removal has a strong association with the oxidation–reduction​ potential. This result confirms that aerobic conditions for VSSF systems promote the removal of the TCS compound. For the case of IB, an association between IB and biological oxygen demand removal was observed. However, this relation was found to be not significant. This study reveals that PCA allows us to determine the association between different variables in VSSF systems. Moreover, this work will serve as the basis for future research for optimizing the performance for removing TCS and IB by focusing on the improvement of aerobic conditions.

Operational performance of corncobs/sawdust biofilters coupled to microbial fuel cells treating domestic wastewater

Biofilters coupled to microbial fuel cells (MFCs) are the most integral treatment technology that generate water-energy nexus for rural zones sanitation. Moreover, biofilters coupled to MFCs, using organic residues as bed filter have not been studied. Therefore, the aim of this study was comparatively to evaluate biofilters based on corncobs/sawdust coupled to MFCs treating domestic wastewater. Biofilters based on corncobs/sawdust (50%, v/v) as bed filter incorporating microorganisms (BM), earthworms/microorganisms (BEM, Eisenia foetida Savigny), plants/microorganisms (BPM, Canna indica L.), and all organisms (HB) were evaluated. These biofilters were coupled to 2 electrochemical systems based on graphite cathodes with graphite (G)/stainless-steel mesh (M) anodes. Three nominal hydraulic loading rates (0.3, 0.5, and 1 m3 m−2 d−1) evaluating removal of organic matter, nutrients and pathogens were monitored. Voltage within electrochemical systems also were registered. Results demonstrated that biofilters based on corncob/wood chips coupled to MFCs reach mean organic matter removal efficiencies over 80% (COD: 86%, BOD5: 91%). Nevertheless, HBG was the most efficient (up to 6%) biofiltration technology monitored. The biofiltration typologies studied reported removal efficiencies of nutrients (NH3-N, PO43−) and pathogens (fecal coliforms) up to 99%. Specifically, BMG and HBG were the biofiltration typologies that registered the highest energy recovery (up to 104 mV, 29 mW m−2). Within all the biofiltration typologies studied, the hybrid biofiltration coupled to MFCs using graphite (HBG) is the one that offers the best water-energy nexus conditions, thanks to its biological complexity.

Operational and biochemical aspects of co-digestion (co-AD) from sugarcane vinasse, filter cake, and deacetylation liquor.

This work performed co-AD from the vinasse and filter cake (from 1G ethanol production) and deacetylation liquor (from the pretreatment of sugarcane straw for 2G ethanol production) in a semi-Continuous Stirred Tank Reactor (s-CSTR) aiming to provide optimum operational parameters for continuous CH4 production. Using filter cake as co-substrate may allow the reactor to operate throughout the year, as it is available in the sugarcane off-season, unlike vinasse. A comparison was made from the microbial community of the seed sludge and the reactor sludge when CH4 production stabilized. Lactate, butyrate, and propionate fermentation routes were denoted at the start-up of the s-CSTR, characterizing the acidogenic phase: the oxidation-reduction potential (ORP) values ranged from -800 to -100 mV. Once the methanogenesis was initiated, alkalizing addition was no longer needed as its demand by the microorganisms was supplied by the alkali characteristics of the deacetylation liquor. The gradual increase of the applied organic load rates (OLR) allowed stabilization of the methanogenesis from 3.20 gVS L-1 day-1: the highest CH4 yield (230 mLNCH4 g-1VS) and average organic matter removal efficiency (83% ± 13) was achieved at ORL of 4.16 gVS L-1 day-1. The microbial community changed along with the reactor operation, presenting different metabolic routes mainly due to the used lignocellulosic substrates. Bacteria from the syntrophic acetate oxidation (SAO) process coupled to hydrogenotrophic methanogenesis were predominant (~ 90% Methanoculleus) during the CH4 production stability. The overall results are useful as preliminary drivers in terms of visualizing the co-AD process in a sugarcane biorefinery integrated to scale. KEY POINTS: • Integration of 1G2G sugarcane ethanol biorefinery from co-digestion of its residues. • Biogas production from vinasse, filter cake, and deacetylation liquor in a semi-CSTR. • Lignocellulosic substrates affected the biochemical routes and microbial community. • Biomol confirmed the establishment of the thermophilic community from mesophilic sludge.

Insights to improve covered lagoon biodigesters through by-products recovery in pig farms

Pig farming activity has an important role in the Brazilian economy and generates effluents with a high polluting potential. The covered lagoon biodigester is a simple and suitable alternative for the treatment of swine manure. This work aimed to propose improvements to the pig effluent treatment system composed by covered lagoon biodigesters. Therefore, a survey of a typical plant configuration of pig effluent treatment was accomplished and alternatives were suggested in order to get a greater energy sustainability in farms through resource recovery. The proposed interventions were based on studies of scientific papers, technical equipment manuals, technical research and consultation with professionals of the field. The optimization of the systems operation considers some criteria, such as: (i) need for solids removal; (ii) organic loading; (iii) operation temperature; (iv) effluent recirculation; and (v) biogas energy recovery. Firstly, a typical scenario was identified without any improvements, in which the biogas is sent to flares without energy recovery. Subsequently, systems improvement insights were proposed, mainly regarding effluent heating through a solar heating system or by recovering the thermal energy from biogas and biogas recovering. The treatment optimization would increase the efficiency of organic matter removal and biogas production, as well as electric energy production and reduction in greenhouse gases emissions. The use of tools such as Life Cycle Analysis (LCA) can favor decision making and comparing proposed alternatives.

Evaluation of omphacite and iron-coated omphacite as a water filtration medium

Abstract In this study, omphacite medium were modified by roasting at high temperature. The optimal preparation conditions were as follows: the pH value was 1, concentration of FeCl3 was 2 mol/L, roasting temperature was 450 °C and roasting time was 2 h. Specific surface area, scanning electron microscopy, and EDS analysis were used to compare the unmodified and modified omphacite, and a dynamic filtration experiment was performed to treat the slightly polluted water. The analysis of the characterization results revealed that the surface structure of the modified omphacite filter medium changed greatly. Its surface was rough and potholes increased, and the specific surface area and adsorption capacity were significantly increased. Results of the dynamic filtration experiment revealed that the average removal efficiencies of organic matter, TOC, and turbidity by quartz sand were 21.17%, 2.2%, and 94.5%. The average removal efficiencies of organic matter, TOC, and turbidity by unmodified omphacite were 23.46%, 26.7%, and 95.2%. The average removal efficiencies of organic matter, TOC, and turbidity by modified omphacite were 50.35%, 45.5%, and 96.3%. On the whole, the filtration performance of the modified omphacite filter column was the best among the three filter columns, and the recovery of the backwashing performance was also better.

Insights into the electro-hybrid ozonation-coagulation process–Significance of connection configurations and electrode types

The electro-hybrid ozonation-coagulation process (E-HOC) integrates electrocoagulation (EC) and ozonation simultaneously in a single unit. Nevertheless, the performance of the EC process is highly dependent on the polar connection configuration (monopolar vs. bipolar connection) and the type of generated coagulants (single-coagulant vs. dual-coagulants). In this study, the removal efficiency of the E-HOC process with different connection configurations and types of coagulants was assessed. The E-HOC process with bipolar connection (BE-HOC) exhibited higher removal efficiency for wastewater treatment plant (WWTP) effluent organic matter and ibuprofen (IBP) compared with the E-HOC process with monopolar connection (ME-HOC). Furthermore, dual-coagulant generation (released from both Al and Fe electrodes) in the BE-HOC process greatly improved the WWTP effluent organic matter and IBP removal efficiency. Lower energy consumption was observed for the BE-HOC process compared with the ME-HOC process. It was found that ozonation promoted the polymerization reactions during coagulant hydrolyzis in the E-HOC process. Compared with the ME-HOC process, the BE-HOC configuration and dual-coagulant mode further facilitated polymeric hydrolyzed coagulant species formation, thereby improving ozone catalytic and coagulation performance. According to trapping experiments and EPR analysis, •OH formation was enhanced in the BE-HOC process and dual-coagulant mode. In addition, more active reaction sites of generated hydrolyzed coagulant species were observed with bipolar connection and in the dual-coagulant generation mode based on X-ray photoelectron spectroscopy (XPS) analysis.

Upgrading of waste stabilization ponds using a low-cost small-scale fine bubble diffused aeration system.

Waste Stabilization Ponds (WSPs) are known for the economical treatment of wastewater, especially if low-cost land is available. In this research to overcome some common operational problems such as undesirable color changes in ponds, severe odor problems, and most importantly, deviations from the effluent standards, the performance of a novel installation of a small-scale fine bubble diffused aeration system in the inlet zone of the facultative pond has been investigated. The long-term operational data of the system in two wastewater treatment plants in the east of Iran demonstrated that this system can significantly improve the efficiency of the treatment plant in addition to eliminating the mentioned operational problems. Pre-aeration of the inlet zone of the facultative ponds (Birjand WSPs) by the aeration system consists of 250 fine bubble disk diffusers (12 inches in diameter) and one 22 kW roots blower showed that purple color and odor problem can eliminate after almost two weeks and organic matter removal efficiency increased from 58 ± 15% to about 85 ± 10% based on BOD5. Almost similar results were obtained from the WSPs of Neyshabur. Long-term experimental results showed this system can be used successfully to control the process and upgrade these natural and efficient treatment processes, especially in developing countries.

Influence of low and high dosages of methyl and propyl parabens on membrane bioreactor (MBR) performance

ABSTRACT This study aimed to evaluate the degradation of methylparaben (MeP) and propylparaben (PrP) in synthetic wastewater in a membrane bioreactor (MBR) whose operation involved three stages: stage 1 (stabilization period), with no addition of parabens; stage 2, in which the MBR was fed with 0.5 mg L−1 of each paraben; and stage 3, in which both MeP and PrP were added, at 10 mg L−1each. The system performance was assessed by monitoring pH, temperature, effluent flow rate, transmembrane pressure, BOD, COD, suspended solids, and paraben concentration. The results confirmed that the MBR showed a good organic matter removal efficiency (> 92.2% for BOD; >91.6% for COD) and was not significantly affected by the addition of parabens at either low or high dosages. The volatile to total suspended solids ratio remained nearly constant, suggesting that the addition of parabens at a high concentration did not negatively impact the control of suspended solids. It was possible to achieve 96.0% of MeP and PrP removal in stage 2 ([parabens]0 = 0.5 mg L−1), and 86.0% of PrP removal in stage 3 ([PrP]0 = 10 mg L−1). Finally, biodegradation was found to be the main removal mechanism of parabens in the investigated MBR.

Simultaneous energy production, boron and COD removal using a novel microbial desalination cell

This paper investigates simultaneous boron removal from aqueous solutions, organic matter removal from industrial wastewater and energy production using a Microbial Desalination Cell (MDC). Anode chamber of the conventional MDC cell was modified to include 3D cubic electrodes as a novel design. Effects of operating parameters, including electrode type (3D-electrode and 2D-electrode), anolyte solution temperature (20 °C, 40 °C, and 60 °C), and activated sludge:wastewater volumetric ratio (S:WW = 1:1, 1:2, and 1:5), on MDC performance were studied. Furthermore, real geothermal water treatment was investigated under optimum operating conditions. Boron and organic matter removal efficiencies and the produced power density results were promising for 3D-electrodes under optimum operating conditions. The maximum boron removal efficiency, COD removal efficiency, and power density were 55.5%, 91.5%, and 9.04 mW/m3 treating real geothermal water at optimum operating conditions. The analyses of Scanning Electron Microscope with Energy Dispersive X-ray spectrometer (SEM-EDX) demonstrated biofilm formation and salt deposition on membrane surfaces, which most probably reduced the performance of MDC. Consequently, our results showed that use of 3D-electrodes was a promising improvement to the conventional configurations with 2-D electrodes since removal efficiencies and energy production were comparable for a more compact electrode structure.

Bioaugmentation Technology for Treatment of Toxic and Refractory Organic Waste Water Based on Artificial Intelligence.

With the development of modern chemical synthesis technology, toxic and harmful compounds increase sharply. In order to improve the removal efficiency of refractory organic matter in waste water, the method of adding powdered activated carbon (PAC) to the system for adsorption was adopted. Through the analysis of organic matter removal rule before and after waste water treatment, it can be found that PAC is easy to adsorb hydrophobic organic matter, while activated sludge is easy to remove hydrophilic and weakly hydrophobic neutral organic matter. Powdered activated carbon-activated sludge SBR system (PAC-AS) system is obviously superior to AS and PAC system in removing organic matter of hydrophilic and hydrophobic components, that is, biodegradation and PAC adsorption are additive. Compared with the control system, the Chemical Oxygen Demand (COD) removal rate of refractory substances increased by 8.36%, and PAC had a good adsorption effect on small molecular weight organic compounds, but with the increase of molecular weight of organic compounds, the adsorption effect of PAC gradually weakened, and it had no adsorption effect on macromolecular organic compounds. Based on the research of fuzzy control theory, an Agent control system for ozone oxidation process of industrial waste water based on Mobile Agent Server (MAS) theory was established, which was realized by fuzzy control method. The simulation results showed strong stability and verified the feasibility and adaptability of the distributed intelligent waste water treatment system based on MAS theory in the actual control process.

The effectiveness of anode variations for electrocoagulation and its application for laundry wastewater treatment

Since Diponegoro University moved its campus to the Tembalang area, it has been full of issues of decreasing groundwater quality and aesthetic decline caused by laundry wastewater and washing and toilet wastewater which has growing rapidly along with the growth of boarding houses in the Tembalang area. This will have an impact on the health quality of the people who live in the Tembalang area. This study aims to reduce the content of dissolved organic matter in laundry wastewater and bath wash also bath, wash and toilet wastewater. The method chosen was the electrocoagulation method, using 2 different electrodes. The electrodes chosen are aluminum metal and ferrous metal (as anode) and carbon (as cathode). With the electrocoagulation method using aluminum electrodes (as anode) and carbon (as a cathode) the amount of organic material that could be removed was 60.1%. Meanwhile, with ferrous metal (as anode) and carbon (as cathode) the amount of organic material that can be removed is smaller, namely 52.2%. The addition of 100 ppm NaCl solution and 100 ppm Na2SO4 solution was able to increase the efficiency of organic matter removal by 1.8-2.5%.

Production of a coagulant by electrocoagulation for the treatment of drinking water

ABSTRACT The main objective of this study is the application of electrocoagulation to produce a coagulant for drinking water treatment using aluminium plates recovered from waste of aluminium door and window manufacturing workshop. The influence of the optimum operating conditions controlling electrocoagulation was defined for different parameters such as electrolyte concentration, pH of the medium, plate number (electrodes) and contact time. The results showed that 47.6 g of coagulant was obtained for pH equal to 4 and electrolyte concentration of 0.04 mol L−1 with four electrodes for the period of 1 day. The produced coagulant was characterised by structural analysis (FTIR), analysis by scanning electron microscopy (SEM) and physical analysis by BET. Thus, the coagulant prepared was used in conjunction with the commercial flocculant (polymer) to evaluate their performance to removal efficiency of organic matter (~97%), turbidity (82.61%) and the aluminium ions (Al3+) concentration (50%) in raw water.

Influence of activated sludge dissolved oxygen concentration on a membrane bioreactor performance with intermittent aeration

This study measured the effect of low activated sludge dissolved oxygen (DO) concentration on a membrane bioreactor (MBR) treating real urban wastewater with respect to organic matter and nitrogen removal efficiency and transmembrane pressure evolution. For this purpose, a full-scale experimental pre-denitrification MBR system was operated at a constant permeate flow rate of Q = 0.45 m3h−1 with intermittent aeration. The experimental installation worked at high hydraulic retention time, variable sludge retention time and with activated sludge temperatures of between 22.0 to 31.3 °C. Mean DO concentrations in the activated sludge were gradually decreased from 1.25 mgO2L−1 to less than 0.20 mgO2L−1. Variations in DO set points did not affect the main operational parameters of the MBR system and no clear relation was shown between DO concentration decrease and membrane fouling. At DO concentrations lower than 0.2 mgO2L−1, a deterioration in MBR effluent quality was observed, mainly with respect to chemical oxygen demand, biochemical oxygen demand at five days and NH4 +, however, the opposite effect was observed for NO3 -. These results indicate that employing low DO set points is a promising strategy for application in MBR systems.