Chemical Oxygen Demand Concentration Research Articles

Three-dimensional electro-Fenton system with steel-slag based particle electrode for the treatment of refinery spent caustic

Refinery spent caustic (RSC) is a highly contaminated wastewater originated from the petroleum refining industry with complicated chemistry and high toxicity. In this work, a novel three-dimensional electro-Fenton (3DEF) system assisted by electromagnetic induction was developed to treat an actual RSC with a chemical oxygen demand (COD) concentration of 27000–33000 mg/L. Industrial waste steel slag was used as both the particle electrode and the Fenton’s catalyst. Under optimal conditions, COD removal reached 93.6% within 90 min. Electromagnetic induction significantly enhanced COD degradation by promoting the corrosion of steel slag, inhibiting the electrode passivation, and enhancing the thermal activation of hydrogen peroxide. The reusability of steel slag was also enhanced by electromagnetic induction. Radical quenching tests demonstrate that hydroxyl radicals (•OH) played a main role in the pollutant degradation. The system is of good economic and environmental benefits with a total treatment cost of about 1.015 $/m3, achieving the objective of “treating waste with waste”.

Accounting for the microbial assembly of each process in wastewater treatment plants (WWTPs): study of four WWTPs receiving similar influent streams.

We evaluated a unique model in which four full-scale wastewater treatment plants (WWTPs) with the same treatment schematic and fed with similar influent wastewater were tracked over an 8-month period to determine whether the community assembly would differ in the activated sludge (AS) and sand filtration (SF) stages. For each WWTP, AS and SF achieved an average of 1-log10 (90%) and <0.02-log10 (5%) reduction of total cells, respectively. Despite the removal of cells, both AS and SF had a higher alpha and beta diversity compared to the influent microbial community. Using the Sloan neutral model, it was observed that AS and SF were individually dominated by different assembly processes. Specifically, microorganisms from influent to AS were predominantly determined by the selective niche process for all WWTPs, while the microbial community in the SF was relatively favored by a stochastic, random migration process, except two WWTPs. AS also contributed more to the final effluent microbial community compared with the SF. Given that each WWTP operates the AS independently and that there is a niche selection process driven mainly by the chemical oxygen demand concentration, operational taxonomic units unique to each of the WWTPs were also identified. The findings from this study indicate that each WWTP has its distinct microbial signature and could be used for source-tracking purposes.IMPORTANCEThis study provided a novel concept that microorganisms follow a niche assembly in the activated sludge (AS) tank and that the AS contributed more than the sand filtration process toward the final microbial signature that is unique to each treatment plant. This observation highlights the importance of understanding the microbial community selected by the AS stage, which could contribute toward source-tracking the effluent from different wastewater treatment plants.

THE EFFECT OF IMMOBILIZED ENZYME ON TEXTILE WASTEWATER

Textile wastewater has a complex composition characterized by high dye content and chemical oxygen demand. Therefore, textile wastewaters have serious environmental impacts, such as aesthetic degradation, and carcinogenic properties. Treatment and the recovery of textile wastewater are important due to their high volume and toxicity. The effects of peroxidase enzyme immobilized on magnetic chitosan-clay beads of synthetic textile wastewater were investigated in a batch reactor. System performance was determined by chemical oxygen demand (COD) and color. The batch reactor was operated in three different pH (5, 7, 10), temperatures (25, 35, 45 °C), and reaction times (0-5-10-20-30 min.) with synthetic textile wastewater. As a result, COD and color removal efficiencies were determined as 44% and 56%, respectively, corresponding effluent concentrations are 1442 mg/L, 450 Pt-Co. The results of this study show that using the enzyme immobilization process is an effective method to remove color and COD concentration from textile wastewater.

Utilization of UV–Vis and synchronous fluorescence heterospectral two-dimensional correlation analysis on the structural variation of landfill leachate during membrane bioreactor-reverse osmosis process

Landfill leachate, a complex organic effluent generated during the sanitary landfilling process, poses a significant environmental threat if not properly managed. This study utilized fluorescence and UV–Vis spectroscopy in conjunction with two-dimensional correlation spectroscopy (2DCOS) to investigate the removal and transformation properties of landfill leachate during membrane bioreactor (MBR) and reverse osmosis (RO) processes. The results revealed that the MBR process effectively reduced the concentrations of chemical oxygen demand and total organic carbon, but had limited impact on complex structures and bio-refractory organic matter. Conversely, the RO process demonstrated effective trapping of organic pollutants, including both fluorescent and non-fluorescent components. Furthermore, 2DCOS analysis identified the sequence of changes in landfill leachate substances: unsaturated aldehydes and ketones > fulvic-like component/protein-like component > aromatic compounds. These findings offer valuable insights for the development of economical and efficient landfill leachate treatment procedures.

Acidogenic fermentation of biowaste coupled with nitrogen recovery using selective membranes to produce a VFA-rich liquid with a high C/N ratio

This research focuses on the production of a liquid stream rich in volatile fatty acids (VFAs) and low ammoniacal nitrogen content (<0.1 g N/L) from biowaste. The liquid stream was obtained by combining (i) mixed culture acidogenic fermentation to maximise VFA production and (ii) gas-permeable membrane (GPM) contactor to recover ammoniacal nitrogen. Three batch fermentation tests of biowaste collected in a full-scale mechanical-biological treatment plant provided high and stable VFA concentrations (37–39 g CODVFA/L). VFAs represented 73–81 % of the soluble chemical oxygen demand (sCOD) concentration, with a predominance of acetic, propionic and butyric acids. A highly specialized microbial community was observed in all batch tests, with Bacteroidota and Firmicutes as predominant phyla (>90 % of relative abundance). The GPM contactor recovered more than 99 % of the ammoniacal nitrogen in the fermentation liquid without VFA losses. The suitability of the produced fermentation liquid with a high C/N ratio for downstream applications was evaluated using biomethane potential tests (BMP) at different total ammonium nitrogen (TAN) concentrations (0.76–3.15 g N/L) and circumneutral pH. Despite achieving similar ultimate methane yields (279–314 NmL CH4/g CODfeed), lower TAN concentrations in the biowaste fermentation liquid improved anaerobic biodegradation kinetics, enhancing its potential applicability for methane production.

A novel approach for purifying food waste anaerobic digestate through bio-conditioning dewatering followed by activated sludge process: A case study

Although anaerobic digestion is the mainstream technology for treating food waste (FW), the high pollutant concentration in the resultant food waste anaerobic digestate (FWAD) often poses challenges for the subsequent biochemical treatment such as activated sludge process. In this study, taking a typical FW treatment plant as an example, we analyzed the reasons behind the difficulties in treating FWAD and tested a novel process called as bio-conditioning dewatering followed by activated sludge process (BDAS) to purify FWAD. Results showed that high concentrations of suspended solids (SS) (16439 ± 475 mg/L), chemical oxygen demand (COD) (24642 ± 1301 mg/L), and ammonium nitrogen (NH4+-N) (2641 ± 52 mg/L) were main factors affecting the purification efficiency of FWAD by the conventional activated sludge process. By implementing bio-conditioning dewatering for solid-liquid separation, near 100% of SS and total phosphorus (TP), 90% of COD, 38% of total nitrogen (TN), and 37% of NH4+-N in the digestate could be effectively removed or recovered, consequently generating the transparent filtrate with relatively low pollution load and dry sludge cake (<60% of moisture content). Furthermore, after ammonia stripping and biochemical treatment, the effluent met the relevant discharge standards regulated by China, with the concentrations of COD, TN, NH4+-N, and TP ranging from 151 to 405, 10–56, 0.9–31, and 0.4–0.8 mg/L, respectively. This proposed BDAS approach exhibited stable performance and low operating costs, offering a promising solution to purify FWAD in practical engineering and simultaneously realize resource recovery.

A cathodic electro-fermentation system for enhanced methane production from high-concentration potato starch industrial wastewater

The high chemical oxygen demand (COD) concentration of potato starch industrial wastewater makes it very challenging for traditional anaerobic digestion (AD) to treat. Here we proposed to use the cathodic electro-fermentation system to enhance the methane production from potato starch industrial wastewater (7546 mg·L−1 COD). Compared with the traditional AD, the electro-fermentation system enhanced the maximum methane production rate more than three times and increased the cumulative methane production by 30 %. What's more, the lag phase of the AD was dramatically reduced, and the COD degradation rate was significantly improved in the electro-fermentation system. The better performance could be attributed to the fact the electro-fermentation system could avoid the accumulation of the intermediate metabolites (e.g. volatile fatty acids (VFAs)) and maintain a suitable pH for methanogens. Additionally, the applied potential at the cathode enhanced the acidification and methanation process and enabled a more stable microbial community. This study demonstrated that electro-fermentation is an efficient way to treat high-concentration potato starch industrial wastewater for methane production.

Polyacrylamide degradation in oil field wastewater by UV/H2O2 and UV/PDS: Rapid experimental measurement and model simulation

Ultraviolet-based advanced oxidation processes (UV-AOPs) are effective for degrading refractory pollutants in wastewaters. However, performing rapid efficiency evaluations represents a significant challenge for process selection and optimization in practical application. This study investigated polyacrylamide (PAM) degradation by UV/hydrogen peroxide (H2O2) and UV/potassium peroxydisulfate (PDS) in pure water and practical oil field wastewater. Based on a previously developed mini-fluidic photoreaction system that is easy to operate and requires low sample volumes, an experimental setup for rapid evaluation of UV-AOP efficiency was constructed that enabled on-line analyses of viscosity, UV absorbance, and pH via specially fabricated flow cell devices together with off-line analyses of PAM, chemical oxygen demand (COD), and acrylamide (AM). The PAM degradation rate constants (k′PAM) in practical oil field wastewater by UV/H2O2 and UV/PDS were 2.4 and 2.1 m2 einstein−1, respectively, which were much higher than those by sole UV process (0.8 m2 einstein−1). Combing with the analyses of viscosity, UV absorbance (220 nm), pH, COD, and AM concentration, the UV/H2O2 and UV/PDS demonstrated the effectiveness in PAM degradation in oil field wastewater. Additionally, the scavenging capacities of HO• and SO4•− of practical oil field wastewater were determined, and the k′PAM values were predicted by model simulation and verified experimentally. This study provides rapid evaluation methods for UV-AOP efficiencies, which is helpful for selecting and optimizing UV-AOPs for industrial wastewater treatments.

Optimization of operational parameters using central composite design in the peroxi‐alternating current‐electrocoagulation process for the pollutant removal with determination of power consumption from industrial wastewater

AbstractThe utilization of electrochemical and advanced oxidation technologies for industrial wastewater (IW) treatment has grown in popularity during the last two decades. The effectiveness of several methods for treating IW, including hydrogen peroxide (H2O2), direct‐current (DC) and alternating‐current (AC)‐electrocoagulation (EC), and the combination of H2O2 with DC/AC‐EC (H2O2‐DC/AC‐EC) processes were all investigated. In comparison to the H2O2, DC/AC‐EC, and H2O2‐DC/AC‐EC technologies, the results showed that the H2O2‐AC‐EC process produced 100% total colour and 100% chemical oxygen demand (COD) removal efficiency with a low power consumption of 4.4 kWhm−3. The H2O2/AC‐EC technology was optimized for treating IW using a response surface methodology approach based on a central composite design using a five‐factor level. Utilizing statistical and mathematical techniques, the optimum parameters were determined to minimize consumption of power (1.02 kWhm−3) and maximum COD elimination (75%). The experimental parameters comprised the following: H2O2 of 600 mg/L, current of 0.65 Amp, pH of 7.6, COD of 1600 mg/L, and treatment time (TT) of 1.26 h. When using a Fe/Fe electrode combination with the wastewater pH of 7, the COD removal efficiency was shown to be enhanced by increasing the TT, current and H2O2, and decreasing the COD concentration. The synergistic impact, quantified as the combined efficiency of eliminating % COD utilizing the H2O2, AC‐EC, and H2O2/AC‐EC procedures, was found to be 15.75%. Therefore, employing a hybrid H2O2‐AC‐EC approach is considerably more effective in treating IW.

Combination of pozzolan and sawdust as biofilter for textile wastewater treatment

Background: Inappropriate management of textile wastewater results in environmental pollution. To counter this, biofilters or biofilm systems serve as alternatives. Biofilters work like a filter, with a media stack that aids in the filtration process. In this study, pozzolan and sawdust were used as media. The present study aimed to identify the difference in average color content, chemical oxygen demand (COD), and chromium of textile wastewater after passing through a single biofilter versus a combination biofilter. Methods: This study employs a post-test with a control design experimental research design. The research population is the total textile wastewater produced by the X industry located in Cimahi city, Indonesia. The grab sampling technique was employed to collect 30 L of textile wastewater for each treatment using both the single biofilter (composed solely of sawdust) and the combination biofilter (mixture of sawdust and pozzolan). Results: There are significant differences in color, COD, and chromium content averages between single and combined biofilter treatments, supported by P values of 0.012, 0.004, and 0.010. The single biofilter exhibited higher percentage reductions in color and chromium (14.25% and 90.83%, respectively) compared to the combination biofilter. In contrast, the combination biofilter achieved a remarkable COD reduction of up to 79.45%compared to the single biofilter. Conclusion: The results of the present study showed that the single biofilter had a higher capacity to remove color and chromium compared to the combination biofilter. Meanwhile, the combination biofilter was found to be more effective in removing COD compared to the single biofilter.

From drainage to resource: a practice approach to reuse greywater for household irrigation purposes

Abstract The United Nations indicates that available freshwater resources will decrease significantly due to pollution growth and urbanization; two-thirds of the world's population may face water shortages by 2030. Extended use of greywater is an alternative option for reducing potable water consumption in urban areas. Recently, the reuse of treated greywater for home gardens, peri-urban agriculture, and landscaping has become a widespread concern in many developing countries. This paper presents a study on a low-cost system that can perform greywater treatment for household use. This treatment system employed physical filtration by ceramic filters, quartz gravel, hollow fiber membrane, and UV disinfection. Three greywater samples collected from the kitchen, washing basins, and bathroom were investigated. The operation process determines the system's effectiveness by considering turbidity, coliform, Biochemical Oxygen Demand (BOD5), and Chemical Oxygen Demand (COD) concentration of the inlet and outlet water. As a result, high removal efficiency (i.e., &amp;gt;60%) could be obtained for each investigated parameter. Results also showed that grey water generated from washing basins has the highest potential for reuse since the water quality after treatment satisfies the water reuse standards for household irrigation. The findings encourage further exploration and implementation of greywater reuse practices.

Green nanocatalyst for the photocatalytic degradation of organic pollutants in petroleum refinery wastewater: Synthesis, characterization, and optimization

The synthesis of green nanocatalysts is an emerging branch of current nanotechnology due to its numerous advantages, including high efficiency, sustainability, cost-effectiveness, biocompatibility, and eco-friendliness. In this study, a thermal technique was employed to prepare a novel green nanocatalyst (GNC) from the sepals of waste tomato (WT) plants, and this GNC was investigated to determine its efficiency in degrading the chemical oxygen demand (COD) during a photocatalytic process of simulated petroleum refinery wastewater (PRW). The characterization of the waste tomato-green nanocatalyst (WT-GNC) was performed using various techniques, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), Brunauer–Emmett–Teller (BET) analysis, and Fourier-transform infrared (FTIR) spectroscopy, which revealed that the synthesized WT-GNC possessed an excellent catalytic quality. This work examined the key factors affecting the degradation rates, such as the type of light source (UV or LED) and its arrangement (outside or inside the reactor), aeration rate, pH, catalyst dose, irradiation time, temperature, and initial COD concentration. The WT-GNC degraded 99.9 % of the COD (residual = 1 ppm) under the optimal operating conditions (pH = 7, WT-GNC dose = 0.25 g/L, irradiation time = 90 min, temperature = 25 °C, and initial COD = 1326 ppm) under UV lamps located around the inside of the reactor wall. Ultraviolet (UV) light is highly effective in degrading the COD compared to visible LED lights. The reaction followed the pseudo-first-order kinetic model (R2= 0.998) with k = 0.0367 min−1. The WT-GNC exhibited good reusability and stability and could reduce 76.3 % of the COD after the fifth consecutive cycle. Therefore, this novel GNC can serve as a cost-effective, efficient, stable, and eco-friendly photocatalyst to lower the COD of PRW to meet the World Health Organization (WHO) standards. In addition, it can be recovered and reused several times.

Biodegradability and bioavailability of dissolved substances in aquaculture effluent: Performance of indigenous bacteria, cyanobacteria, and green microalgae

Aquaculture is a controlled aquatic farming sector and one of the most important human food sources. Fish farming is one of the predominant, fast-growing sectors that supply seafood products worldwide. Along with its benefits, aquaculture practices can discharge large quantities of nutrients into the environment through non-treated or poorly treated wastewater. This study aims to understand the nutrient composition of fish wastewater and the use of indigenous bacteria, cyanobacteria, and microalgae as an alternative biological treatment method. Wastewater samples from a local fish farming facility were collected and treated using six different species of cyanobacteria and microalgae include Chroococcus minutus, Porphyridium cruentum, Chlorella vulgaris, Microcystis aeruginosa, Chlamydomonas reinhardtii, and Fischerella muscicola. All the samples were incubated for 21 days, and the following parameters were measured weekly: Chemical oxygen demand (COD), phosphate, total dissolved nitrogen, and dissolved inorganic nitrogen. In addition, dissolved organic nitrogen (DON), bioavailable DON (ABDON), and biodegradable DON (BDON) were calculated from the mass-balance equations. Colorimetric and digestive methods were used for the parameter measurements. The results showed that C. reinhardtii reduced the soluble COD concentration by 74.6 %, DON by 94.3 %, and phosphorous by more than 99 %. Moreover, M. aeruginosa, and C. minutus significantly reduced inorganic nitrogen species (>99 %). This alternative fish wastewater treatment method was explored to gain insight into fish wastewater nutrient composition and to create a sustainable alternative to conventional fish wastewater treatment methods.

Biofilm Growth of Pseudomonas Aeruginosa Tgc04 Exposed to Metformin and Variations in Cod Content

Purpose: This work aimed to evaluate the biofilm formation of Pseudomonas aeruginosa TGC04 exposed to 100 and 200 µg/mL of metformin, varying the Chemical Oxygen Demand (COD) and flow regime. Theoretical framework: Metformin is an oral antidiabetic agent with antimicrobial properties, excreted in an active and unmetabolized form. Like some non-antibiotic drugs, subinhibitory concentrations of metformin may contribute to the expression of microbial resistance in wild-type strains. Methods: After the Minimum Inhibitory Concentration (MIC) of metformin was known, nine microcosms were filled with 500 mL of synthetic wastewater with Chemical Oxygen Demand (COD) at 10,000 and 1,000 mg/L in the presence of MIC and sub-MIC of metformin. Two incubation conditions were tested, with and without aeration (4 L/min). Biofilms were quantified after 2 and 24 hours at 25ºC by the crystal violet test. Results and conclusion: It was observed reductions and increases in biofilm growth around 13 and 64%, respectively. The greatest biofilm growth occurred in cells exposed to 200 µg/mL of metformin. Both the flow regime and COD concentration were important for the development of the biofilm, whose cells were mostly weakly to moderately adhered. Research implications: This work showed that wild strain P. aeruginosa colonize biofilms in the presence of non-antibiotic drug with antimicrobial activity. Originality/value: The study provides evidence that in polluted aquatic systems with turbulent regimes, the inhibitory concentration of metformin promoted the least disturbances to the biofilm.

The influence of various chemical oxygen demands on microbial fuel cells performance using leachate as a substrate.

Microbial fuel cells (MFCs), hailed as a promising technology, hold the potential to combat various wastewater pollutants while simultaneously converting their chemical energy into electricity through biocatalysts. This study explores the applicability of a dual compartment MFC (DC-MFC) under varying conditions, targeting the removal of chemical oxygen demand (COD) from landfill leachate and electricity generation. In this setup, anaerobic sludge from a wastewater treatment plant serves as the inoculum in the anode compartment of the MFC, with a Nafion117 membrane acting as the separator between MFC units. The cathode compartments are filled with distilled water and continually aerated for 24 h to enhance air supply. The study assesses the MFC's performance across different COD concentrations, focusing on COD removal, power generation, and Coulombic efficiency. The findings reveal that COD removal efficiency is notably enhanced at higher concentrations of organic matter. Specifically, at a COD concentration of 3325.0 mg L-1, the MFC exhibited the highest COD removal efficiency (89%) and maximum power density (339.41 mWm-2), accompanied by a Coulombic efficiency of 25.5%. However, as the initial substrate concentration increased to 3825 mg L-1, the efficiency decreased to 72%, with a Coulombic efficiency of 13.56% and a power density of 262.34 mWm-2. Optical density levels increased due to bacterial growth at ambient temperature and neutral pH, reflecting the dynamic microbial response within the system.

Effect of Orifice Induced Hydrodynamic Cavitation on the Properties of Waste Activated Sludge

Exploring alternative methods to reduce the quantity of wastewater sludge and improve its characteristics is among the prioritized subjects in the field of sludge management. Hydrodynamic cavitation, commonly employed for water and wastewater treatment, also holds the potential for utilization as a pre-treatment method for sludge. In the presented study, the excess sludge obtained from the wastewater treatment facility of a food and beverage manufacturing factory was collected and disintegrated with a orifice-induced hydrodynamic cavitation unit. According to the data obtained, the highest cavitation performance was achieved under the condition where the cavitation number was set to 0.3. In addition, hydrodynamic cavitation performed under the optimum operating conditions, significantly increased the solubility of waste activated sludge. The results showed that the soluble chemical oxygen demand concentration, which was initially determined as 382 mg/l, reached 3,068 mg/l end of the cavitation. 64% of the total Kjeldahl nitrogen and 60% of the total phosphorus of waste-activated sludge were converted into soluble forms by the effects of hydrodynamic cavitation. Moreover, the results of the microbial study indicated that removal rates of indicator bacteria varied between 94% and 99%.

Direct Membrane Filtration of Wastewater: A Comparison between Real and Synthetic Wastewater

In this study, a lab scale direct membrane filtration (DMF) system using ultrafiltration membranes was operated to compare synthetic and real wastewater to evaluate their membrane fouling propensity and the partitioning of organics and nutrients during concentration. For fouling prevention, cyclic operation was used which consisted of 90 s of filtration followed by 15 s of relaxation and backwashing conducted every 15 min. The system was tested at a high initial flux of 80 LMH (L/m2·h), and the trials were run until a 90% volume reduction was achieved for each batch. Both the synthetic and real wastewater showed similar fouling propensities and organic and nutrient partitioning. The synthetic and real wastewater had an average flux of 46.3 LMH and 28.5 LMH and an average total chemical oxygen demand rejection of 90.3% and 83.1% after 30 h of operation, respectively. The recovery of organics was similar in both influents, resulting in 65.5% and 64.0% of the total chemical oxygen demand concentrations in the concentrate stream for synthetic and real wastewaters, respectively. The total phosphorous and nitrogen concentrations were also similar in terms of rejection rates resulting in 85% and 78% for the synthetic and 89% and 65% for the fresh WWs, respectively. The comparison revealed that synthetic wastewater, though not identical to real wastewater, can serve as a surrogate in DMF studies. This will help to remove one of the key sources of variability in current DMF studies and will allow for more rapid development of DMF technology.

Anaerobic co-digestion of low Chemical oxygen demand concentration sludge mixture by different pretreatment methods

&lt;p&gt;Three laboratory scale systems were operated to study the anaerobic co-digestion of sewage sludge with the excess activated sludge and cattle manure which contained low COD concentration. The experiments were performed to evaluate the effects of different methods of pretreatment. Since the poor organic substrate, the organic loading rate(OLR) was designed about 1.6kg total solids(TS)(l *d)-1 and the hydraulic retention time was controlled from 78days to 53days throughout the experiment to investigate the effects of the input on overall stability. When the digesters got stabilized, the COD removal efficiencies were 61%, 89% and 54%, respectively, and the pH value fluctuated little in the three digesters. The results indicated that the treatment of 1g volatile solids(VS) of SSEASCM on semi-continuous co-digestion generated more than 200ml of biogas on average. Thus, anaerobic co-digestion of the mixed sludge provided a means for low COD waste treatment and produced renewable energy.&lt;/p&gt;&#x0D;

Periodic injection of liquefied kitchen and food waste in municipal solid waste: Effects on leachate and gas generation

With continuous advancements in the zero-waste strategy in China, transportation of fresh municipal solid waste to landfills has ceased in most first-tier cities. Consequently, the production of landfill gas has sharply declined because the supply of organic matter has decreased, rendering power generation facilities idle. However, by incorporating liquefied kitchen and food waste (LKFW), sustainable methane production can be achieved while consuming organic wastewater. In this study, LKFW and water (as a control group) were periodically injected into high and low organic wastes, respectively. The biochemical characteristics of the resulting gas and leachate were analyzed. LKFW used in this research generated 19.5–37.6 L of methane per liter in the post-methane production phase, highlighting the effectiveness of LKFW injection in enhancing the methane-producing capacity of the system. The release of H2S was prominent during both the rapid and post-methane production phases, whereas that of NH3 was prominent in the post-methane production phase. As injection continued, the concentrations of chemical oxygen demand, 5-d biological oxygen demand, total organic carbon, ammonia nitrogen, total nitrogen, and oil in the output leachate decreased and eventually reached levels comparable to those in the water injection cases. After nine rounds of injections, the biologically degradable matter of the two LKFW-injected wastes decreased by 8.2 % and 15.1 %, respectively. This study sheds light on determining the organic load, controlling odor, and assessing the biochemical characteristics of leachate during LKFW injection.

Application of electro oxidation process for treating wastewater from petrochemical with mixed metal oxide electrode

Petrochemicals require a large volume of water for their operation, which results in the production of a large volume of wastewater. Treatment of petrochemical wastewater is an important process before discharging it into the environment. This research examines the treatment of real petrochemical wastewater using the electrochemical oxidation process. Direct anodic oxidation is an effective advanced electrochemical oxidation process (AEOP), with different electrodes using a parallel plate electrochemical reactor. Four types of real wastewater were received from different petrochemical units were treated by AEOP. Real wastewater samples with chemical oxygen demand (COD) concentrations ranging from 20,450 to 52,300 mg/l. The main goal of this research is to make electrodes of Mixed Metal Oxide (MMO), which can reduce the treatment time and electricity consumption for oxidation, greater stability of the surface of the electrodes. Investigation of the rate constant kinetics shows that high COD removal efficiency can be achieved following the pseudo-second order reaction rate (R2 > 98%). When the wastewater pH is less than 5, COD removal efficiency is higher and the treatment process will be successful, which succeeded in removing 79% COD, but in alkaline wastewater, COD reduction efficiency was not satisfactory. The electricity consumption for 79% removal during 6 min was 117 kWh/m3. As a result, due to the very short time of the process (6 min), it can be used as one of the pre-treatment steps of petrochemical wastewater with acidic pH.