COD Abatement Research Articles

Decolorization enhancement of basic fuchsin by UV/H2O2 process: optimization and modeling using Box Behnken design

The present work deals with the optimization of basic fuchsin dye removal from an aqueous solution using the ultraviolet UV/H2O2 process. Response Surface Modeling (RSM) based on Box-Behnken experimental design (BBD) was applied as a tool for the optimization of operating conditions such as initial dye concentration (10–50 ppm), hydrogen peroxide dosage (H2O2) (10–20 mM/L) and irradiation time (60–180 min), at pH = 7.4 under ultra-violet irradiation (254 nm and 25 W intensity). Chemical oxygen demand (COD abatement) was used as a response variable. The Box–Behnken Design can be employed to develop a mathematical model for predicting UV/H2O2 performance for COD abatement. COD abatement is sensitive to the concentration of hydrogen peroxide and irradiation time. Statistical analyses indicate a high correlation between observed and predicted values (R2 > 0.98). In the BBD predictions, the optimal conditions in the UV/H2O2 process for removing 99.3% of COD were found to be low levels of pollutant concentration (10 ppm), a high concentration of hydrogen peroxide dosage (20 mM/L), and an irradiation time of 80 min.

Integrated physicochemical processes to tackle high-COD wastewater from pharmaceutical industry

Wastewater decontamination in pharmaceuticals is crucial to prevent environmental and health risks from API residues and other contaminants. Advanced oxidation processes (AOPs) combined with cavitational treatments offer effective solutions. Challenges include designing reactors on a large scale and monitoring the effectiveness and synergies of the hybrid technology. In the present work, pilot-scale treatment of a real high COD (485 g/L) pharmaceutical wastewater (PW) was investigated using hydrodynamic cavitation (HC) operated individually at 330 L/h or in combination with oxidants and electrical discharge (ED) with cold plasma (15 kV and 48 kHz). The first approach consisted of PW cavitational treatment alone of 7 L of 1:100 diluted PW at a HC-induced pressure of 60 bar and a flow rate of 330 L/h. However, this strategy did not provide satisfactory results for COD (∼15% less), and only when HC treatment was extended to more than 30 min in a recirculation mode, encouraging results were obtained (∼45% COD reduction). Consequently, a hybrid approach combining HC with ED-cold plasma was chosen to treat this high-COD PW. Aiming to establish an efficient flow-through hybrid process, after optimising all cavitation and electrical discharge parameters (45 bar HC pressure and 10 kHz ED frequency), the best COD abatement of ∼50 % was recorded with a 1:50 diluted PW. However, a subsequent adsorption step over activated carbon was required to achieve an almost quantitative COD reduction (95%+). Our integrated physicochemical process proved to be extremely efficient in treating high-COD industrial wastewater and resulted in a remarkable reduction of the COD value. In addition, the residual surfactants content in the PW were also drastically reduced (98%+) when a small amount of oxidants was added in the hybrid HC/ED treatment.

Abatement of a complex mixture of dyes in the presence of chlorides by electrocoagulation and active chlorine-based photoelectro-Fenton-like processes

This paper presents an innovative hybrid water treatment process combining electrocoagulation (EC) and active chlorine-based PEF-like (PEF-like) methods to eliminate a complex mixture of tannery dyes. The solution contained Acid Blue 113 (AB 113), Acid Blue 29 (AB 29), and Brilliant Green (BG) dyes in concentrations between 300 and 750 mg L−1 COD in 2000 mg L−1Cl−, 638 mg L−1NH4+ and 1700 mg L−1SO42− at neutral pH (resembling wastewater). The influence of mean linear flow velocity (0.69 ≤ u ≤ 3.47 cm s−1), applied current density (6 ≤ j ≤ 22 mA cm−2), and initial COD on the EC removal efficiency and discoloration was systematically examined. EC removed 32–48% COD; this modest depletion is due to the high load of organic matter. On the other hand, the •OH and HClO produced in the PEF-like process were insufficient to mineralize the organic matter (52–76%) due to the high initial COD. The latter suggested that the PEF-like process requires a previous EC to reduce the COD. The synergy between EC + PEF-like (hybrid process) allowed the COD abatement. The dye removal efficiency followed the order EC < PEF-like < EC + PEF-like. The hybrid process fulfilled the Mexican standard (COD < 210 mg L−1, and 100% discoloration) with total treatment costs of 0.683–0.696 USD m−3. XRF, XRD, SEM-EDS, OEA, and FTIR analyses on iron flocs indicated that AB 29, AB 113, and BG dyes are removed by adsorption. HPLC techniques followed the maleic and malic acids and ammonium and sulfate ions during the incineration of the dyes. The hybrid technology is promising for treating real wastewater containing complex dye mixtures.

Reclamation of pharmaceutical wastewater by UAF, contact oxidation, and auto brush-cleaning aiding nano ZrO2 coated ceramic membrane MBR - an industrial-scale practice and functional microbial diversity

This project aimed to assess the feasibility of applying UAF/contact oxidation followed by ceramic membrane MBR in reclaiming 1400 m3/day of pharmaceutical wastewater with COD and NH4+-N of around 8400 and 135 mg/L, respectively. UAF and contact oxidation system employed novel porous lightweight ceramsite as microbial carriers to facilitate the biomass retention. Results revealed that the integrated biological treatment experienced excellent and stable performance in the operation of successive 160 days in terms of COD and NH4+-N abatement, around 96.8% and 81%, respectively. With the aid of auto mechanical bush and air scouring in submerged flat-sheet nano ZrO2 coated ceramic membrane MBR for mitigating the membrane fouling, the MBR exhibited stable and better performance to remove suspended solid and soluble microbial products with around flux of 25 LMH and no severe fouling was observed during the whole treatment process. The MBR effluent can be reclaimed for road cleaning, urban landscaping, etc. Miseq sequencing analysis in the sludge-day 160 indicated that UAF was rich in Firmicutes with 42.02% relative abundance, followed by Thermotogae (22.91%) and Bacteroidetes (13.59%), which can decompose macromolecules into small molecules. Moreover, some species in Thermotogae and Bacteroidetes accounted for generation of biofilm in the ceramsite in UAF. Genus Petrotoga played a key role in conspicuous COD removal in UAF. The bacterial species composition in contact oxidation exhibited substantially discrepant. Appearance of Proteobacteria, as the dominant phylum (41.7%) can be responsible for COD abatement. Genus Thauera, Acinetobacter and Aeromonas detected had the capacity in NH4+-N removal.

Influence of salinity on heavy metal and oil removal from hypersaline oilfield-produced water by electrocoagulation: mechanistic insights.

The focus of the present study was to explore how and to what extent ultrahigh salinity affects the adsorption of cadmium and hydrocarbon pollutants onto aluminum hydroxide adsorbents formed in an electrocoagulation process. The changes in the nature and structure of the electro-generated aluminum particles and the possible removal mechanisms due to high salt content were investigated by using FE-SEM/EDS, FTIR, BET, and XRD analyses. The pseudo-second order and Freundlich models proved to fit the data for cadmium adsorption onto the aluminum hydroxides best. It was demonstrated that the adsorption capacities were significantly affected by the high salinity. With the rise of the salinity from 2 to 170g/L, the cadmium and COD removal yields dropped from 81 to 60% and from 90 to 72%. The increase of the oil content led to the enhanced cadmium adsorption capacity due to surface complexation and ion exchange mechanisms. It was proved that Lagergren pseudo-first-order kinetic model could justify COD abatement trends. FTIR spectra depicted that the negative impact of high salinities on the adsorption was due to causing the formation of less stable adsorbents. According to BET analysis, the occurrence of much wider pore size distribution and smaller specific surface area in high salinity case was the main reason for the decreased adsorption capacity. Based on XRD analysis, the higher crystallinity of the produced aluminum hydroxide particles and their consequential smaller surface areas resulted in the lower adsorption capacity in the hypersaline environment. It was concluded that adsorption via inner-sphere and outer-sphere complexation and sweep flocculation were the possible removal mechanisms. Total treatment cost of 8.75 and 3.49 €/m3 were estimated for low and ultrahigh salinity conditions.

Use of a cascade system based on marine sand and bottom ash in the treatment of cardboard manufacturing wastewater by infiltration percolation

The production of electrical energy in thermal power plants generates huge quantities of solid waste (fly ash and bottom ash). The valorization of these by-products becomes imperative for safeguarding the environment. The fly ash is used in the manufacture of cement; but locally, it is not the case of the bottom ash that is buried in landfills. In this paper, we present the results of wastewater treatment of a cardboard plant by an optimized prototype cascade station (scale: 1/1000). The succession of filter beds consists of crude bottom ash, crushed bottom ash, and coastal sands in appropriate proportions. The filtrate at the outlet of each floor is analyzed. Respecting the current regulations, the desired parameters are the suspended solids (TSS), COD, BOD5, pH, and trace elements (As, Fe, Zn). The results of the tests allowed us to reach a COD abatement is 85%. When leaving the 3rd floor, it was 94.5% and finally, at the exit of the fourth, it is 95%, an important reduction of BOD5. At the exit of the 2nd floor, the abatement is 75.6%, at the exit of the 3rd, it is 78.6%. Finally, an overall rate of 79% was obtained, a significant TSS reduction up 95.6% at the output of the 2nd floor. By leaving the 3rd floor, it is 96.12%. Overall, the developed system achieves a TSS abatement rate TSS of 96.34%.and the elimination of trace elements such as zinc, iron, and arsenic (84%, 48%, and 57% respectively).

Oxygen supply management to intensify wastewater treatment by a microbial electrochemical snorkel

The microbial electrochemical snorkel (MES) is a low-cost, low-maintenance technology that could considerably reduce wastewater treatment costs by reducing the need for aeration. An MES is a single electrode. The lower part, in the anoxic zone of the bioreactor, oxidizes organic matter by transferring electrons to the electrode. The upper part, in the oxic zone, releases the electrons by reducing dissolved oxygen. This study gives new insights into the correlation between the MES potential, the concentration of dissolved oxygen and COD abatement, thus enabling practical rules to be extracted for running the MES in optimal conditions, particularly for adjusting the aeration zone and frequency.Here, aeration promoted the cathodic reaction and increased the MES potential to a maximum (0.0 to 0.1 V/SCE). After aeration stopped, the potential dropped to a minimum (< -0.4 V/SCE). With 26 cm high MESs, sequential aeration at the top was not sufficient to support an effective cathodic zone, while aeration at the bottom was detrimental to the formation of the microbial anode. With MESs 48 cm high and aeration set up in the highest quarter, 30 minutes of aeration every 4.5 hours gave potential variations that were stable for weeks. The MESs continued to oxidize organic matter 30 minutes after the aeration had stopped. In this period, the MESs removed 3 to 6.3 times more COD than the control reactors. Increasing the electrode capacitance is therefore suggested as an effective way to further decrease the aeration cost by decreasing the aeration frequency.

Long term catalytic activity of pyrite in Heterogeneous Fenton-like oxidation for the tertiary treatment of dyeing wastewater

The long term catalytic activity of pyrite in advanced oxidation for wastewater treatment is vital for the practical application. In this work, the efficacy of pyrite catalyzed Fenton-like oxidation for tertiary treatment of dyeing wastewater was investigated for a period of two years. The influence of pyrite oxidation and dissolution on the catalytic activity was studied based on surface characterizations and chemistry studies. Experimental results demonstrated that pyrite can effectively catalyze H2O2 to oxidize recalcitrant pollutants in the biological effluent of dyeing wastewater. At initial pH 3–6, H2O2 of 10 mM and pyrite of 24 g L−1, COD and color removals reached 76.67% and 97.09% in 180 min of reaction time. The higher treatment efficacy of pyrite catalyzed Fenton-like oxidation was due to appropriate conversion rate of H2O2 to hydroxyl radicals compared with the classic Fenton oxidation. Heterogeneous catalysis by Fe(II) on the pyrite surface was much more significant than Homogeneous catalysis by dissolved iron ions of pyrite. The latter contributed only 28.25% abatement of COD at pH 3 and can be negligible at wastewater initial pH > 5. The oxidation of pyrite resulted in acidic pH environment for recalcitrant organic compound destruction even if the initial pH of wastewater was 6.5. It was found that the catalytic activity of pyrite can maintain at least two years, as the surface regeneration of pyrite in that period of time occurred spontaneously due to the slow dissolution of oxidation products.

Electrochemical Degradation of Amoxicillin on a Ti/Ta2O5/Pt-RuO2-IrO22 Electrode

This work deals with the degradation of Amoxcillin which is one of the antibiotics commonly used in human and veterinary medicine. For such an investigation, Pt-RuO2-IrO2 (PRI) electrode was used as anode and various parameters such as current density (20 - 100 mA/cm2), supporting electrolyte and chloride were monitored. The results showed that the amoxicillin oxidation reaction is diffusion controlled and its degradation rate increases as the applied current increases. The degradation of amoxicillin on the PRI electrode, in the absence of chloride, is very low with less than 10% of the COD abatement rate. But, in the presence of chloride, the degradation of the Amoxicillin on PRI electrode leads to its mineralization. During electrolysis, chloride was oxidized into chlorine under the form HClO at pH - at pH > 8 that contribute to a significant degradation of the Amoxicillin. The amoxicillin removal rate goes from 0.83% to 73.8% in the absence and in the presence of Cl-, respectively after 10 h of electrolysis. In addition, the degradation kinetic of amoxicillin in HClO4 is 10 times faster than in KClO4 and follows pseudo first-order reaction.

Treatment of real domestic sewage in a pilot-scale aerobic granular sludge reactor: Assessing start-up and operational control.

Aerobic granular sludge (AGS) has been considered a breakthrough in the wastewater treatment sector given its key characteristics, such as excellent settleability, simultaneous removal of organic and nutrient pollutants, and compactness. However, the formation of granules often delays the start-up of granular-based systems, especially in large-scale settings. This study addressed the start-up of a pilot-scale AGS sequencing batch reactor (SBR) treating domestic sewage, monitored for over 280days. The challenges faced during aerobic granulation using a mixture of activated sludge and anaerobic granular sludge as inoculum and the performance of the reactor on organic matter, nitrogen, and phosphorus removal were discussed. Results showed that robust and stable granules were formed after an initial period of around six months, with the settling time playing a key role on granules development. At least 80% of granules had a diameter greater than 0.2mm and 60% >1mm. In general, the reactor achieved high nitrogen removal efficiency, as well as satisfactory removal of soluble COD. However, total COD abatement was impaired by the various episodes of suspended solids loss with the effluent. Overall, this study demonstrated that the reactor was efficient in the treatment of domestic sewage, but its performance was adversely affected from sudden changes in the influent quality. PRACTITIONER POINTS: Aerobic granular sludge (AGS) applied to small-scale domestic sewage treatment. The control of sludge age in AGS can be a problem due to short sedimentation times. High DO to maintain aerobic granulation can economically make the process economically unfeasible in tropical countries. A sludge with excellent sedimentation properties was obtained. However, maintaining the granule over time is a challenge.

Platinum nanoparticles embedded into polyaniline on carbon cloth: improvement of oxygen reduction at cathode of microbial fuel cell used for conversion of medicinal plant wastes into bio-energy

ABSTRACT A microbial fuel cell is a biological electrochemical system that extracts electrons stored in organic matter by oxidation using catalytic properties of microorganisms at bioanode. The major problem in such device, is however limited power production due to slow kinetic of oxygen reduction at cathode. It is worthwhile to develop new materials that fulfil these requirements. The polymerization of aniline onto carbon cloth for effective electrodeposition of platinum nanoparticles has been carried out by chronoamperometry and cyclic voltammetry. Three materials were thus elaborated, namely pristine carbon cloth, carbon cloth modified with platinum and carbon cloth modified by polymerization of aniline for immobilization of Pt-nanoparticles. The FTIR spectroscopy analysis revealed characteristic band located in 1720–1650 cm−1, attributed to imine function, main component in skeleton of polymer PANI chain. The modified materials have been utilized as cathode in cell inoculated with medicinal plant wastes for improvement of oxygen reduction. Modified cathode with CC-PANI-Pt proved higher performances in all respects: increase of cell voltage from 338 to 765 mV and power density from 862 to 1510 mW/m2 and abatement of COD of microbial inoculum leachate to 88%. Another feature of cell with modified cathode CC-PANI-Pt, was the enormous electric charge density harvested upon oxidation of 1 mL of acetate 7.62 C/cm2 compared to that of cell with pristine CC cathode 0.54 C/cm2. Nevertheless, coulombic efficiency for conversion of medicinal plant wastes into bioenergy was relatively lower 9%, making in evidence that elaborated electrochemical device was rather efficient and benificial environmentally than energetically.

Optimization of photocatalytic degradation of rhodamine B using Box-Behnken experimental design: Mineralization and mechanism.

The aim of this work was to optimize the photocatalytic degradation of rhodamine B (RhB) using a four-factor Box-Behnken experimental design, and the study was carried out under artificial irradiation (24-W UV lamp) using ZnO in suspension. The Box-Behnken model has been validated with an error less than 5%. A total (100%) RhB removal and COD abatement rates were reached under optimal conditions of treatment time, ZnO dose, and stirring speed at different concentrations of dye. The study of the effect of irradiation type (solar and UV lamp) on the degradation of RhB showed that solar irradiation gave a better rate of degradation with complete discoloration after 2hr. The study of RhB degradation mechanism indicates that were the main active species for the degradation of this pollutant. The comparison between the degradation of RhB alone and RhB prepared with varnish (as it is usually used in industry) revealed that degradation of RhB alone is faster comparing than that of RhB/varnish mixture. The results showed that the biodegradability was improved after a contact time of 60min with a BOD5 /COD ratio increasing from 0.23 to 0.90. PRACTITIONER POINTS: Optimization of the photocatalytic degradation of rhodamine B using a four-factor Box-Behnken experimental design. Investigation of dye mineralization. The degradation mechanism of rhodamine. Biodegradability assessment based on the BOD5 /COD ratio.

Micronucleus assay based on Vicia faba roots as a tool to assess the performances of wastewater treatment systems

Abstract In order to evaluate the efficiencies of three wastewater treatment systems (WWTS), the micronucleus (MN) on Vicia faba roots (through soil and liquid matrix) and phytotoxicity tests were investigated on six wastewater treatment plants in Morocco. Results showed that genotoxicity decreased significantly and reached about 100%, 93.5% and 89% during activated sludge, infiltration–percolation and natural lagoon processes respectively. On the other hand, activated sludge showed the best phytotoxicity removal with a germination index (GI) exceeding 100% for cress. By contrast, infiltration–percolation and natural lagooning systems showed a GI of less than 80%. Using redundancy multivariate analyses, toxicity removal was linked to the abatement of COD, TSS and heavy metal. Thus, genotoxicity assessment based on V. faba roots using liquid matrix seemed to be more promising to evaluate WWTS efficiencies.”

Treatment of mixed industrial wastewater by electrocoagulation and indirect electrochemical oxidation

Treatment of mixed industrial wastewater is a challenging task due to its high complexity. This work scrutinizes the electrochemical treatment of mixed industrial wastewater, specifically electrocoagulation and indirect electrochemical oxidation processes through COD and color removal studies. Both processes are found to be more efficient at the wastewater pH. Monopolar connection was found more effective than bipolar connection for the removal of COD and color from wastewater. The monopolar connection removed COD up to 55% and color 56% whereas bipolar connection leads to the removal of 43% and 48% respectively at wastewater pH with an applied voltage 1.5 V in the course of 1 h of electrolysis.In the case of indirect electrochemical oxidation process using graphite electrodes, the COD and color abatement efficiencies of the indirect electrochemical oxidation process were found as 55% and 99.8%, respectively within 1 h of electrolysis conducted at pH 7.7, applied voltage 4 V, and NaCl concentration 1 g L−1. This work also highlights the importance of the presence of electrolytes in the indirect electrochemical oxidation process as the external addition of sodium chloride significantly enhanced both COD and color elimination efficiency.

Evaluation of ozonation applicability to pulp and paper streams for a sustainable wastewater treatment

Pulp and paper wastewater ozonation was tested at pilot-scale in a medium-potentiality wastewater treatment plant (143,000 population equivalent). Single wastewater lines (bleaching and process water), as well as wastewater mixture (before and after secondary biological treatment) were investigated to evaluate the best ozonation conditions. The aim of the work was to evaluate the feasibility of substituting current tertiary physicochemical treatment with an ozonation unit, reducing operating costs and improving management operations. The tests were useful to identify the ozone dosage required to achieve the desired COD abatement. Ozone effectiveness was more pronounced in process water (60% COD removal), rather than bleaching water (28% COD removal); ozone showed a significantly higher efficiency on pulp and paper wastewater mixture after biological treatment (up to 81% COD removal) rather than before biological process (46% mean COD abatement). COD removal efficiency at a dosage of 100 mg O3/L was comparable to existing physicochemical treatment (mean 50%); a good TSS abatement (up to 20–30 mg/L) was observed as well. Toxicity analysis revealed that ozonation treatment did not modify treated effluent toxicity characteristics (mean Daphnia Magna mortality of 23.3%). Economic analysis proved that ozonation installation cost would be 1.5–2.0 M€, for total flowrate to be treated of 1200 m3/h. Ozonation would lead to an economic saving of about 300,000 €/y compared to actual physicochemical treatment and the investment cost could be recovered in about 7 years. The proposed innovative approach, including plant analysis, pilot-ozonation tests, data regression, respirometric fractionation, toxicity and economic analysis, could be exported to other industrial wastewater treatment plants to allow an increased advanced oxidation processes diffusion.

Removal of COD from Industrial Biodiesel Wastewater Using an Integrated Process: Electrochemical-Oxidation with IrO2-Ta2O5/Ti Anodes and Chitosan Powder as an Adsorbent

The production of biodiesel is an energy and water-intensive process that produces wastewater with high concentrations of COD, BOD, and FOG. Conventional treatment processes are not capable of treating contaminants and pollutants in biodiesel wastewater to satisfactory concentrations, and hence, advanced treatment processes are necessary. Untreated discharge of biodiesel wastewater results in additional costs during the production of biodiesel when penalties and fines are applied. In this research, a lab-scale integrated treatment process was used to investigate the successful abatement of contaminants, COD, BOD and FOG, present in industrial biodiesel wastewater. The integrated treatment process consisted of three consecutive steps: acidification, electrochemical oxidation, and adsorption. Acidification as a pre-treatment occurred at a pH of 2. Electrochemical oxidation using IrO2-Ta2O5/Ti anodes at a current density of 1 mA/cm2 and NaCl concentration of 0.08 M was followed by three consecutive adsorption stages using Chitosan powder at a concentration of 4.5 g/L. The experimental results show that the integrated treatment process could reduce COD, BOD and FOG levels by 94%, 86% and 95%, respectively. The treated effluent complies with local industrial effluent discharge standards, which could be disposed of safely without further treatment.

Pilot-UASB reactor tests for anaerobic valorisation of high-loaded liquid substrates in friulian mountain area

This work was focused on the start-up of a pilot-UASB reactor, to valorise high-loaded liquid substrates available in the mountain area of Friuli-Venezia Giulia region; technical and economic convenience of full-scale UASB reactor activation, treating condensate pulp and paper wastewater, was evaluated. Leachate, obtained from organic fraction of municipal solid waste, and cheese whey were studied as well, as alternative feeds for UASB reactor, given the availability of these substrate in the analysed area. The results of the pilot tests highlighted a good adaptation of granular biomass to diluted cheese whey (1:50 v/v), with stable operations (mean COD removal of 84.6%), while lower COD abatements were obtained on condensate water (mean 53.6%) and, mostly, OFMSW leachate (mean 37.0%). Organic loading rate could be progressively increased in a following step, as for cheese whey, augmenting CH4 production (mean obtained yield of 0.149 m3 CH4/kg CODremoved). Condensate water tests were useful to plan the revamping of full-scale UASB reactor: the approximated energy saving in the aerobic line was evaluated as 101.3 kW (2,430 kW h/d). As for OFMSW, it was concluded that alternative different liquid-solid separation methods to percolation, such as mechanical pressing, should be preferred, to increase influent COD (mean obtained value of 750 mg/L), given also the low amount of available waste in the analysed territory (4142 t/year), improving potential energy recovery.

Enhanced anaerobic performance and SMD process in treatment of sulfate and organic S-rich TMBA manufacturing wastewater by micro-electric field-zero valent iron-UASB.

This study focused on investigating reactor performance, simultaneous methanogeneis and denitrifiction (SMD) process for treatment of a sulfate plus organic sulfur - rich 3,4,5-Triethoxybenzaldehyde (TMBA) manufacturing wastewater with variable COD/TSO42- (total sulfate) ratio by micro-electric field- zero-valent-iron (ZVI) UASB for 390 days. The initial COD/TSO42- was set as 1.42, 0.9 and 0.5, respectively by manually introducing sulfate. The experimental results indicated that micro-electric field- zero-valent-iron UASB was an attractive integrated option for satisfactory COD removal, nitrate reduction and a reasonable methane yield rate even at COD/TSO42- as low as 0.9. Further declining the COD/TSO42- to 0.5 can result in a moderate inhibition of SMD process. The behavior of organic S release was not inhibited over the entire experimental period. Thus, surprisingly, sulfate concentration in the effluent was always higher than that in the influent. In comparison with sludge sample at Day-1, sludge at Day-390 was characterized with high abundant Tissierella Soehngenia, Anaerolinaceae and Brevundimonas diminuta, which played critical role in promising performance in COD abatement. The relatively low abundance of sulfate reducing bacteria (SRB) such as Desulfobulbus and Desulfomicrobium can explain the lower sulfate reduction efficiency in term of high concentration of sulfate plus released from organic S-rich compounds.

SUCCESSFUL LANDFILL LEACHATE WASTEWATER TREATMENT USING THE SEQUENCE OF OZONATION, ADSORPTION ON CHARCOAL AND PHOTO-OZONOLYSIS

Landfill leachate derived from the landfilling practice of the municipal wastes is a problem affecting all countries and continents. Even after the shutdown of a landfill site, the leachate production continues for decades. In this work a solution for the landfill leachate treatment has been proposed based on three fundamental steps: the pre-ozonolysis of the leachate, the passage of the ozonized leachate through a fixed bed of activated carbon and the final step consisting in a photo-ozonolysis stage involving the simultaneous action of ozone and UV light. A distinction between the chemical structure and chemical behaviour of young and mature leachate was evidenced by thermal analysis of the soluble organic matter (SOM) obtained from these substrates. Furthermore, a distinction between young and mature leachate was also evidenced in terms of their different reactivity toward ozone as illustrated by the COD abatement and by FTIR spectroscopy on pristine and ozonized SOM. A modular pilot plant for the treatment of different landfill leachates was presented and proposed.

A novel textile wastewater treatment using ligninolytic co-culture and photocatalysis with TiO2

Textile industries produce effluent waste water that, if discharged, exerts a negative impact on the environment. Thus, it is necessary to design and implement novel waste water treatment solutions. A sequential treatment consisting of ligninolytic co-culture with the fungi Pleurotus ostreatus and Phanerochaete crhysosporium (secondary treatment) coupled to TiO2/UV photocatalysis (tertiary treatment) was evaluated in the laboratory in order to discolor, detoxify, and reuse textile effluent waste water in subsequent textile dyeing cycles. After 48 h of secondary treatment, upto 80 % of the color in the waste water was removed and its chemical and biochemical oxygen demands (COD, and BOD5) were abated in 92 % and 76 %, respectively. Laccase and MnP activities were central to color removal and COD and BOD5 abatement, exhibiting activity values of 410 U.L-1 and 1 428 U.L-1, respectively. Subjecting waste water samples to 12h of tertiary treatment led to an 86 % color removal and 73 % and 86 % COD and BOD5 abatement, respectively. The application of a sequential treatment for 18 h improved the effectiveness of the waste water treatment, resultingin 89 % of color removal, along with 81 % and 89 % COD and BOD5 abatement, respectively. With this sequential treatment a bacterial inactivation of 55 % was observed. TiO2 films were reused continuously during two consecutive treatment cycles without thermic reactivation. Removal percentages greater than 50 % were attained. Acute toxicity tests performed with untreated waste water led to a lethality level of 100 % at 50 % in Hydra attenuata and to a growth inhibition of 54 % at 50 % in Lactuca sativa. Whereas sequentially treated waste water excreted a 13 % lethality at 6.25 % and aninhibition of 12 % at 75 % for H. attenuata and L. sativa, respectively. Finally, sequentially treated waste water was reused on dyeing experiments in which 0.86 mg.g-1 adsorbed dye per g of fabric, that is equivalent to 80 % of dye adsorption.