Terms Of COD Reduction Research Articles

Hybrid O3/UV/Fe process using rebar flakes waste for removal of congo red dye in wastewater

In Indonesia, textile is one of the labour-intensive industries that makes an important contribution to the national economy sectors. This industry tends to develop rapidly to meet domestic and export needs. This phenomenon increases wastewater generation from the textile industry. Textile wastewater contains dyes that are designed to be durable to resist sunlight and washing process. These properties pose a challenge to the treatment of dye wastewater. The complex structure of dye molecules is generally difficult to degrade by conventional biological processes, while the physical-chemical precipitation process will generate hazardous sludge. Therefore, alternative treatment processes for dye removal are urgently required. In this work, ozonation (O3), ozone and ultraviolet (O3/UV), and catalytic ozone coupling with ultraviolet (O3/UV/Fe) processes were tested for decolourisation of synthetic Congo red dye wastewater. Laboratory assays were carried out under various operating conditions: pH (3-7); ozonation mode (continuous, sequential); and catalyst dose (0.5-2 g/L). Ozonation in sequential mode and the utilisation of rebar flake waste from building construction project as iron catalyst presents a degree of novelty in this work. Congo red decolourisation up to 97% was achieved in less than one-hour of reaction by the continuous O3 process. Mineralisation in terms of COD reduction (50%) can be increased by either performing ozonation in sequential mode (79%) and coupling with UV irradiation (86%). Nevertheless, the effect of the iron catalyst was found to be negligible.

Remediation of real industrial hypersaline effluent using sequential approach of precipitation followed by cavitation based oxidative process

The current study aims to develop a cost-effective and efficient treatment method for the remediation of amine-containing real industrial effluent. The method consists of a precipitation to remove chloride ions and TDS, followed by cavitation-based AOPs involving US and chemical oxidants as H2O2, O3, Fenton’s reagent, NaClO, and nTiO2. Different parameters including precipitating agent type and dosage, oxidant loading/flow rate, and time were assessed to determine optimal conditions for effective treatment. Treatment schemes were evaluated based on cavitational yield (mg/J), treatment cost (Rs/L), and COD reduction to select an industrially feasible design for amine-containing real effluent treatment. The optimum conditions elucidated were H2O2 loading of 3 g/L, NaClO loading of 3 g/L, O3 flowrate of 3 LPH, nTiO2 loading of 3 g/L, and Fenton’s reagent ratio (H2O2/Fe2+) as 6:1. Under the optimum conditions, US+nTiO2 (70%) treatment schemes were the most efficient, achieving a maximum COD reduction compared to US+Fenton (65%), US+H2O2 (36%), US+O3 (49%) and US+NaClO (53%) schemes. Additionally, impact of chloride and TDS on the oxidation process in terms of COD reduction was assessed. Using Rotavap instead of precipitation, and subsequent use of the best oxidation method (US/HC+Fenton+CaO) achieved COD and TDS levels below 250 mg/L (discharge limit) at optimum conditions, with minimal operating costs of 0.23 $/L and 0.15 $/L, respectively. Overall, the study concluded that the sequential approach of precipitation/Rotavap and cavitation-assisted oxidation is an effective and sustainable method, providing a promising solution for the wastewater treatment in the metallurgical industry.

Direct sludge granulation by applying mycelial pellets in continuous-flow aerobic membrane bioreactor: Performance, granulation process and mechanism

This study provides a sustainable manner for direct cultivation of aerobic granular sludge (AGS) by addition of mycelial pellets (MPs) into continuous-flow aerobic MBR. The results showed that the granulation time in MPs-MBR was shortened by at least 65 days, accounting for enhanced mean size of granules (0.68–0.76 mm), increased mixed liquor suspended solids (MLSS) concentration (12.8 g/L) and improved settling ability (78.1 mL/g), in comparison with that of 0.23–0.28 mm, 9.8 g/L and 102.1 mL/g in control MBR. MPs-MBR demonstrated significant advantages in terms of COD reduction (97.0–99.1%), NH4+-N reduction (100%) and TN reduction (32.27–42.33%). MPs, extracellular polymeric substances (EPS) and filamentous bacteria acted as inducible nucleus, crosslinking matter and supporting skeleton, respectively, in favor of promoting the formation and stabilization of AGS with a four-layered structure. The relevant mechanism was underlined by rheological analysis, indicating that MPs addition enhanced non-Newtonian flow characteristics and network structure of sludge.

Performance of two parallel covered lagoon digesters in the treatment of pig farm wastewaters

Pig farming moves a large part of the Brazilian economy. However, due to the high polluting potential, alternatives to treat and take advantage of the effluents must be developed, being the use of digesters a possible solution. This study aimed to evaluate the performance of two parallel covered lagoon digesters (CLD) in the treatment of swine wastewater. Monitoring was performed on a farm installed in Teixeiras, Minas Gerais, Brazil, in terms of COD in the period from August 2018 to July 2019. The study demonstrated that COD removal efficiency in the CLD was 40.2 and 39.5%, which did not indicate a statistical difference at a 5% significance level. The two digesters in parallel were compatible with each other in terms of COD reduction. Furthermore, individually they did not present significant changes in their performance in the summer and winter periods.

Application of hybrid oxidative processes based on cavitation for the treatment of commercial dye industry effluents

The present work demonstrates the significant role of ultrasound (US) in intensifying the efficacy of the combination with Fenton reagent and/or ozone for the treatment of real dye industry industrial effluent procured from the local industry. Initial part of the work focused on analysing the literature based on combination approaches of US with different oxidants applied for the treatment of real and simulated effluents focusing on the dyes. The work also provides guidelines for the selection of optimal operating parameters for maximizing the intensification of the degradation. The second part of the work presents an experimental study into combined approaches of ultrasound with ozone (O3) and Fenton’s reagent for treatment of real effluent. Under optimized conditions (100 W, 20 kHz and duty cycle of 70%), maximum COD reductions of 94.79% and 51% were observed using a combined approach of US + Fenton oxidation followed by lime treatment for the treatment of effluent-I and effluent-II respectively at H2O2 loading of 17.5 g/L, H2O2/Fe2+ ratio of 3, pH of 4, CaO dose of 1 g/L and an overall treatment time of 70 min. US + Fenton + O3 followed by lime was also applied for treatment under ozone loading of 1 g/h for the treatment of effluent-I and it was found that maximum COD reduction of 95.12% was obtained within 30 min of treatment time, indicating use of ozone did not result in significant value addition in terms of COD reduction but resulted in faster treatment. HC (inlet pressure: 4 bar) + Fenton + Lime scheme was successfully replicated on a pilot-scale resulting in maximum COD reduction of 57.65% within 70 min of treatment time. Overall, it has been concluded that the hybrid oxidative processes as US + Fenton followed by lime treatment is established as the best approach ensuring effective COD reduction at the same time obtaining final colourless/reusable effluent.

Combined hydrodynamic cavitation based processes as an efficient treatment option for real industrial effluent

In the present work, hydrodynamic cavitation (HC) operated alone and in combination with chemical oxidants has been applied for the treatment of real industrial effluent obtained from a local industry. Initially, the analysis of literature related to the hybrid methods involving hydrodynamic cavitation has been presented along with recommendations for the selection of important operating conditions for the HC operated individually and in combination with oxidation processes based on hydrogen peroxide (H2O2), ozone (O3) and persulphate (KPS). Subsequently, the treatment of real industrial effluent has also been investigated in details using HC alone and in combined mode with other oxidation processes focusing on the main objective of COD reduction. The reduction in the COD achieved using individual treatment of HC under the optimized conditions of inlet pressure as 4 bar and pH as 4 was only 7.9%. The application of different hybrid approaches based on HC such as HC + H2O2, HC + O3, HC + KPS and HC + H2O2 + O3 established higher COD reduction as compared to only HC. The maximum extent of COD reduction as 60.8% was achieved using HC + H2O2 + O3 combination whereas, relatively lower extent of COD was achieved for operations of HC + H2O2, HC + O3 and HC + KPS with the actual COD reduction being 40.3%, 38.7% and 8.5% respectively. It was also observed that 30.4%, 28.2%, 15.6%, and 4.7% of TOC reduction was obtained for the combined process of HC + H2O2 + O3, HC + H2O2, HC + O3, and HC + KPS respectively. Based on the kinetic study, it was established that the degradation fitted the first order kinetics for all the approaches. The combined processes of HC with oxidants were also compared with ultrasound reactors (both individual and combined operation) in terms of COD reduction, cavitational yield calculations, and treatment cost. HC reactors were established to be more energy efficient and also yielded treatment costs significantly lower than ultrasonic reactors.

Sonocatalytic treatment of phosphonate containing industrial wastewater intensified using combined oxidation approaches

Treatment of actual industrial wastewater is a challenging task and has not been investigated using the cavitation-based approaches significantly. In the present work, sonocatalytic degradation (catalysts as CuO and TiO2) of phosphonate based industrial wastewater, procured from a local company, has been studied in terms of COD reduction under optimized conditions (established using initial studies involving only ultrasound) of pH as 3.2, the temperature of 32 ± 2 °C and 120 min as treatment time. The combination of ultrasound with H2O2 and ozone in different approaches has been investigated for maximizing the COD reduction. The optimum set of operating conditions for the sonocatalytic degradation were established as power dissipation of 90 W and catalyst loading as 0.75 g/L for CuO and 0.5 g/L for TiO2. Use of only ultrasound resulted in COD reduction of 37.2% whereas the combination of US with different approaches resulted in higher extents of COD reduction. The combined operation of US + H2O2 + O3, US + O3 + H2O2 + CuO, and US + O3 + H2O2 + TiO2 resulted in the extent of COD reduction as 91.5%, 93.8%, and 95.8% respectively. Overall, it has been clearly established that maximum COD reduction is obtained for the combined operation of sonocatalysis (catalyst as TiO2) with ozone and H2O2.

Optimization of reaction parameters for the sonophotocatalytic degradation of hydroquinone

In the present work, the degradation of hydroquinone in synthetic wastewater under sonocatalytic, photocatalytic, and sonophotocatalytic conditions was investigated. The degradation of hydroquinone was investigated in terms of reduction in COD, and the effect of operational parameters including temperature, aeration, frequency, initial hydroquinone concentration, pH, and the TiO2 dose on the sonophotocatalytic process was examined. We focused on items such as the model formation of H2O2 using the sonocatalytic process which was extracted to systemize the operational process and enhance the degradation of hydroquinone. The role and amount of various sizes of the produced bubbles and synergy effect can be detected by our strategy and the integrated system created by the hybrid advanced oxidation process. The degradation values achieved for sonocatalytic, photocatalytic and sonophotocatalytic conditions were approximately 22.3, 76.3, and 100 %, respectively. We found that the maximum hydroquinone degradation in the sonophotocatalysis process was achieved when at a temperature of 25 °C, an aeration of 2 cm3/s, a frequency of 20, 40 and 100 kHZ, a hydroquinone concentration of 100 mg/L, a pH of 7, a TiO2 dose of 20 g/m2, and a fixed radiation intensity of 22.5 µw/cm2. Therefore, the sonophotocatalysis process was selected as the optimal process due to a synergy effect equal to 63.5 %. The highest concentration of H2O2 was observed at the time of the 12th pass equal to 0.136 g/L. The size of the bubbles and the cavitation hole had a significant effect on the H2O2 formation efficiency. The results of this study showed that the sonophotocatalytic hybrid system was able to efficiently degrade hydroquinone compound.

Degradation of C.I. Reactive Dyes (Yellow 17 and Blue 4) by Electrooxidation

Dyes are extensively used in textile industries which are responsible for different environmental problems. Conventional processes for effluent treatment are inefficient for the remediation of wastewaters containing toxic and bio recalcitrant organic pollutants. A large number of advanced oxidation processes (AOP’s) have been successfully applied to degrade pollutants present in wastewaters. This paper examines the use of electro oxidation (EO) process for the recalcitrant of the textile dye effluent. The dye effluent containing C-I Reactive Yellow 17 and Blue 4 was treated using Ti/ RuO2 and stainless steel electrodes. The experimental study focused on the effect of supporting electrolytes such as NaCl and Na2SO4. The degradation process was enhanced appreciably by increasing the concentration of supporting electrolytes at optimum current density of 7 A/dm2 (pH=11). Efficiencies of COD reduction, color removal were also determined. It was established that NaCl was superior to Na2SO4 in terms of COD reduction as well as decolorization. The degradation was characterized by HPLC, FTIR and UV-Vis spectral analysis.

Advanced treatment of industrial wastewater by membrane filtration and ozonization

The present paper deals with nanofiltration (NF), ultrafiltration (UF) and ozonization pilot scale tests for revamping and improvement of an industrial plant that treats wastewaters coming from a wide range of hazardous industrial processes. Tests demonstrated that the best treatment is NF whose feed stream comes from sand filters rather than first ozonization stage before final discharge of the effluent. NF rejection coefficients resulted to be 31% for TDS, 94% COD, 9% Cl–, 47% surfactants, 66% phenols and 91% SO42–. UF was tested as NF pre-treatment but results were not so promising in terms of rejection and permeate flux, as well as fouling reduction. Other experimental tests were carried out in order to understand where to recycle the NF retentate: the best treatment in terms of COD reduction and biodegradability was ozonization followed by recycling to the physico-chemical stage. In the same manner, it was found that ozonization of the NF permeate is the best process solution before final treatment and discharge of the effluent.

Treatment of synthetic textile wastewater by homogeneous and heterogeneous photo-Fenton oxidation

The efficiencies of homogeneous and heterogeneous photo-Fenton oxidation were compared for treatment of azo dye containing synthetic textile wastewater. The influence of parameters such as the presence of NaCl and starch was evaluated and optimal iron and H2O2 dosage determined. Complete decolorization of Remazol Red RR was achieved at all investigated NaCl and starch concentration. Mineralization, in terms of COD reduction, was 96% in the homogeneous and 93% in the heterogeneous reaction, but decreased with increasing NaCl and starch concentrations. The homogeneous oxidation showed the highest efficiency in treating synthetic wastewater containing Remazol Blue RR or a mixture of Remazol Red RR and Remazol Blue RR. Nevertheless, the mineralization was significantly lower than for Remazol Red RR, which shows the dependence on dye structure. Similar amounts of iron-containing sludge were produced in the two processes, while the release of iron ions was reduced by 50% when using heterogeneous photo-Fenton. Promising results were obtained when reusing the iron powder as catalyst; complete decolorization was achieved during 20 batches. (C) 2012 Elsevier B.V. All rights reserved. (Less)

Assessment of microsilica as a value-added material for municipal solid waste clay liner system

This study was carried out to provide landfill clay liner soil along with admixture microsilica in different proportions. The physico-chemical characteristics were carried out to characterise the selected liners. The optimum conditions vis., time of adsorption, adsorbent dosage and pH were studied for the liners. The optimum pH values for COD removals are determined for clay soil, mix 1 : 20, mix 1 : 10 composites as 5, 6 and 6 and optimum contact times are 45, 60 and 60 minutes, respectively. The correlation coefficients of isotherm analysis reveals that Freundlich isotherm for clay soil, mix 1 : 20 and mix 1 : 10 composites ( 0.90, 0.88 and 0.78) shows better fit as compared with Langmuir isotherm. The adsorption capacities in terms of COD reduction by two soil liners revealed that the microsilica addition has not altered the characteristics of clay soil. Hence, microsilica can be used as municipal solid waste leachate since it is an abundant and large quantity available waste material to use as adsorbent.

Biological treatment of natural rubber latex centrifugation effluent using activated sludge system enriched with Bacillus sp. SBS25

Natural rubber latex centrifugation effluent is highly polluting and it is difficult to process because of its high COD and BOD coupled with the excessive amounts of suspended solids. A bacterial strain Bacillus sp. SBS25, isolated from soil, was found to possess natural rubber latex degrading ability. It was exploited in the treatment of the latex centrifugation effluent along with the native flora of the effluent. The treatment with free cells of selected bacteria showed 68% reduction in COD while the fill and draw treatment method in an activated sludge reactor using the consortia and the selected isolate resulted in 92.5% reduction. The performance of the activated sludge reactor was evaluated in terms of reduction in COD, MLSS and SVI.

Electrochemical oxidation and reuse of tannery saline wastewater

In this present work, electrochemical treatment of saline wastewater with organic (protein) load was studied. The influence of the critical parameters of electro-oxidation such as pH, period, salt concentration and current density on the reduction of organic load was studied using graphite electrodes. It was found that current density of 0.024 A/cm 2 for a period of 2 h at pH 9.0 rendered best results in terms of reduction in COD and TKN. The energy requirement for the reduction of 1 kg of TKN and 1 kg of COD are 22.45 kWh and 0.80 kWh respectively at pH 9 and 0.024 A/cm 2. Reuse experiments were conducted at commercial scale. One of the saline waste streams in leather manufacturing process, pickling was treated and reused continuously thrice. The characteristics of the waste stream and the quality of the leathers indicate that the reuse of saline streams with intermittent electrochemical treatment is feasible.

Biomethanation of poultry litter leachate in UASB reactor coupled with ammonia stripper for enhancement of overall performance

In the present study possibility of coupling stripper to remove ammonia to the UASB reactor treating poultry litter leachate was studied to enhance the overall performance of the reactor. UASB reactor with stripper as ammonia inhibition control mechanism exhibited better performance in terms of COD reduction (96%), methane yield (0.26 m 3 CH 4/kg COD reduced), organic loading rate (OLR) (18.5 kg COD m −3 day −1) and Hydraulic residence time (HRT) (12 h) compared to the UASB reactor without stripper (COD reduction: 92%; methane yield: 0.21 m 3 CH 4/kg COD reduced; OLR: 13.6 kg COD m −3 day −1; HRT: 16 h). The improved performance was due to the reduction of total ammonia nitrogen (TAN) and free ammonia nitrogen (FAN) in the range of 75–95% and 80–95%, respectively by the use of stripper. G/L (air flow rate/poultry leachate flow rate) in the range of 60–70 and HRT in the range of 7–9 min are found to be optimum parameters for the operation of the stripper.

Subcritical mineralization of sodium salt of dodecyl benzene sulfonate using sonication—wet oxidation (soniwo) technique

Subcritical mineralization of sodium salt of dodecyl benzene sulfonate via hybrid process—sonication followed by wet oxidation (SONIWO) has been investigated. Sonication of the compound enhanced the rates and % COD reduction during wet oxidation. In this process, homogenous CuSO 4 catalyst was found to be effective. In wet oxidation studies, phenol, hydroquinone, maleic acid, oxalic acid, propionic acid, and acetic acid were identified as intermediates. The global rate equations for wet oxidation in terms of COD reduction were developed.

Modelling the Performance of a Non-steady State Continuous Aeration Plant for the Treatment of Pig Slurry

The performance of a non-steady state aeration process for treating pig slurry has been modelled, using a combination of engineering and microbiological concepts. Performance was defined in terms of COD reduction but estimation of temperature was also necessary both as an intermediate step in estimating the COD/BOD level, and also to identify conditions which fell outside the optimal range of mesophilic activity. Two models are presented and referred to as RM (running mean) and IS (incremental step). The first model used steady-state equations for heat balances and COD predictions with input values averaged over preceding days. The second model used a combination of a microbial model for population and substrate (BOD) level and a heat flow imbalance to predict temperature changes. Model constants were established using data on temperature and COD reduction from a 2000 ha farm scale trial in which operating conditions were varied throughout. The models were then tested, on data from a 1000 ha trial carried out a year later: both followed the changing COD and temperature of the treated slurry with predicted values within 20% of those measured. Despite its greater sophistication, the IS model provided no improvement in prediction over the simpler RM model. This may be the consequence of imprecise and incomplete data, and highlights the limitation of a more rigorous approach to a complex microbial system that exists in a slurry treatment plant.