Initial Chemical Oxygen Demand Concentration Research Articles

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.

Treatment of Dairy Wastewater by Electrocoagulation using Iron Filings Electrodes

This study investigated the treatment of dairy wastewater using the electrocoagulation method with iron filings as electrodes. The study dealt with real samples collected from local factory for dairy products in Baghdad. The Response Surface Methodology (RSM) was used to optimize five experimental variables at six levels for each variable, for estimating chemical oxygen demand (COD) removal efficiency. These variables were the distance between electrodes, detention time, dosage of NaCl as electrolyte, initial COD concentration, and current density. RSM was investigated the direct and complex interaction effects between parameters to estimate the optimum values. The respective optimum value was 1 cm for the distance between electrodes, (60 – 120) min for detention time, 250 mg NaCl/L added, C0/6 = 5,775 mg COD/L as initial COD concentration, and 7.884 - 8.077 mA/cm2 as current provided. At the optimum parameter values, the optimum COD removal efficiency was 73.4%. Meanwhile, the study also performed removal efficiency for nitrogen (N) and phosphate (P) due to their effects on the aquatic life and systems. The optimum removal efficiency for phosphorus and nitrogen was 98.0% and 80.3%, respectively. Due to its effects on the environment and to comply with local legislations, treating these wastewaters using eco-friendly processes was highly recommended taking in consideration the economic feasibility, flexibility and easiness to operate. In addition, the study proved that the high surface area for iron filings played a crucial role in removing process.

The influence of pollutantson plant growth and treatment efficiency of horizontally-constructed wetlands

Constructed wetlands (CWs) have been widely used for wastewater treatment due to advantages such as low cost and easy operation. However, pollutant concentrations directly affect treatment efficiency by inhibiting plant and microbial growth. This study aims to evaluate the relationship between pollutant concentrations, tolerance of plants, and treatment efficiency of horizontal subsurface flow (HSF) CWs receiving synthetic wastewater. The results showed that Cyperus alternifoliusL. grew well in conditions with concentrations of chemical oxygen demand (COD) and NH4+ up to 75 and 125 mg/l, respectively, and pH 5-8. The lowest treatment efficiency was 56.7% at an initial COD concentration of 1000 mg/l. There were several dead plants in the CWs with a NH4+ concentration of 200 mg/l. When the initial COD and NH4+ concentrations were in the range of 500-750 and 75-125 mg/l, respectively, the treatment efficiencies of organic matter (COD) and NH4+ were 82.5-85.1 and 31-69.7%, respectively. The pH value was stable at a neutral level during the treatment process. The concentration ranges of COD (500-750 mg/l) and NH4+ (75-125 mg/l) were the optimal thresholds for pollution control while also ensuring normal plant growth. This study serves as a basis for considering wastewater characteristics in the design of HSF CW systems in practice.

Removal kinetics of organic carbon from palm oil mill effluent by native duckweeds and its potential as a biofertilizer

In the present study, the potential of Azolla pinnata as a phytoremediator of organic carbon and nutrients from palm oil mill effluent (POME) was examined. Seventy-two plastic containers each containing 2 L of POME with four Chemical Oxygen Demand (COD) concentrations (35, 70, 110, and 200 mg/L) and 5 g of A. pinnata with four plastic containers as a control contaminant for each COD concentration were examined. The results have shown that A. pinnata could take up and accumulate organic carbon (COD) and the nutrients (phosphate (PO₄3−), nitrate nitrogen (NO3-N), and ammonia nitrogen (NH3-N)) with a high removal efficiency. The kinetic data of COD were found to follow a pseudo-second-order kinetic model, especially at concentrations within 70 to 200 mg/L (R2 > 98.75 %). A pseudo-first-order kinetic model best fits the initial COD concentration of 35 mg/L (R2 = 95.98 %). The Langmuir-type isotherm best described the COD uptake capacity (qe) (12.5, 9.5, 7.3 and 4.6 mg COD/g adsorbent) by plant sorption for initial COD concentrations of 200, 110, 70, and 35 mg/L, respectively. The findings from this study indicated that POME can be utilized by A. pinnata as a cultivation medium leading to the recovery of biomass as a biofertilizer for better sustainability development goals.

Potential application of a newly isolated microalga Desmodesmus sp. GXU-A4 for recycling Molasses vinasse

The development of cost-effective and energy-efficient technologies for the stabilization of organic wastewater by microalgae has been essential and sought after. In the current study, GXU-A4 was isolated from an aerobic tank treating molasses vinasse (MV) and identified as Desmodesmus sp. based on its morphology, rbcL, and ITS sequences. It exhibited good growth with a high lipid content and chemical oxygen demand (COD) when grown using MV and the anaerobic digestate of MV (ADMV) as the growth medium. Three distinct COD concentrations for wastewater were established. Accordingly, GXU-A4 removed more than 90% of the COD from molasses vinasse (MV1, MV2, and MV3) with initial COD concentrations of 1193 mgL−1, 2100 mgL−1, and 3180 mgL−1, respectively. MV1 attained the highest COD and color removal rates of 92.48% and 64.63%, respectively, and accumulated 47.32% DW (dry weight) of lipids and 32.62% DW of carbohydrates, respectively. Moreover, GXU-A4 grew rapidly in anaerobic digestate of MV (ADMV1, ADMV2, and ADMV3) with initial COD concentrations of 1433 mgL−1, 2567 mgL−1, and 3293 mgL−1, respectively. Under ADMV3 conditions, the highest biomass reached 13.81 g L-1 and accumulated 27.43% DW of lipids and 38.70% DW of carbohydrates, respectively. Meanwhile, the removal rates of NH4–N and chroma in ADMV3 reached 91.10% and 47.89%, respectively, significantly reducing the concentration of ammonia nitrogen and color in ADMV. Thus, the results demonstrate that GXU-A4 has a high fouling tolerance, a rapid growth rate in MV and ADMV, the ability to achieve biomass accumulation and nutrient removal from wastewater, and a high potential for MV recycling.

Applying Eco Enzyme to Reduce Chemical Oxygen Demand (COD) Content of Artificial River Water

Eco enzyme is claimed to improve the quality of polluted water. However, the low pH of eco enzyme solutions can acidify water. The objective of this study was to investigate the effectiveness of eco enzyme in reducing the COD of river water and its effect on the pH of sterilized synthetic river water. The effect of 0.01%, 0.5%, and 1% enzyme concentrations on the COD and pH of synthetic river water with an initial COD of 240 mg/l was investigated. The results showed that eco enzyme itself has high concentration of COD and low pH. The undiluted eco enzyme increased the COD and decreased the pH of both neutralized and non-neutralized synthetic river water. At a 1% eco enzyme concentration and neutral pH, the COD increased in the beginning of experiment and had decreased only by 31.7% after 6-8 days. The COD concentration in this steady state condition had a higher value than that of the initial COD concentration in the river water. This study showed that adding only eco enzyme to synthetic river water is not effective in reducing its COD content.

Comparative Study on Enhanced Photocatalytic Activity of Visible Light-Active Nanostructures for Degradation of Oxytetracycline and COD Removal of Licorice Extraction Plant Wastewater

This study evaluates the effects of carbon, nitrogen, and sulfur dopants on the photocatalytic activity of TiO2 for degradation of oxytetracycline (OTC) and chemical oxygen demand (COD) removal from licorice extraction plant wastewater (LEPW). Three novel visible-light-responsive nanostructures, including L-Histidine-TiO2, L-Methionine-TiO2 and L-Asparagine-TiO2, were successfully synthesized. The results showed that the modification of TiO2 with these three amino acids made the catalyst active in the visible light region and reduced the recombination rate of e−/h+ pairs according to PL analysis. The photodegradation efficiency of L-Histidine (2 wt.%)-TiO2 was 100% and 94% for OTC and COD, respectively. It showed the highest photocatalytic activity under illumination, compared to L-Methionine (1.5 wt.%)-TiO2 and L-Asparagine (2 wt.%)-TiO2. Synthesized composites were characterized with SEM, XRD, FTIR, DRS, and PL analyses. The biological oxygen demand to COD (BOD5/COD) ratio for treated LEPW was determined to be 0.5–0.6, confirming the enhanced biodegradability of the treated effluent. The effect of the independent variables, namely, initial concentration of OTC and COD, catalyst dosage, irradiation time, pH of solution, and light intensity, on the photocatalytic process was evaluated by Response Surface Methodology (RSM), and the optimum value of each independent parameter for maximum degradation of OTC and COD by L-Histidine (2 wt.%)-TiO2 was determined. The radical trapping experiment was performed with various scavengers in order to propose a photocatalytic mechanism, showing that hydroxyl radicals were the main active species. L-Histidine (2 wt.%)-TiO2 showed a stable and reusable structure even after four cycles of COD removal under the following optimal conditions of [COD]: 300 mg/L, [catalyst]: 1 g/L, light intensity: 25 W/cm2 at pH = 4 after 180 min irradiation.

The effects of influent chemical oxygen demand and strigolactone analog concentration on integral biogas upgrading and pollutants removal from piggery wastewater by different microalgae-based technologies

Microalgae-based technologies are promising strategies for efficient wastewater treatment and biogas upgrading. In this study, three types of microalga-fungi/bacteria symbiotic systems stimulated with the strigolactone analog (GR24) were used to simultaneously remove nutrients from treated piggery wastewater and CO2 from biogas. The effects of initial concentrations of chemical oxygen demand (COD) and GR24 on nutrient removal and biogas upgrading were investigated. When the initial COD concentration was 1200 mg/L, the Chlorella vulgaris–Ganoderma lucidum–endophytic bacteria co-cultivation systems achieved the best photosynthetic performance and microalgae growth. Moreover, under the appropriate COD concentration (1200 mg/L), the highest nutrient/CO2 removal efficiencies were obtained. In addition, 10−9 M GR24 significantly accelerated nutrient/CO2 removal efficiencies. These findings provide a theoretical basis for scale-up experiments using microalgae-based technologies

Combining natural zeolite and electrocoagulation with different electrode materials – electrode surface analysis and Taguchi optimization

The treatment of compost leachate by the combined use of natural zeolite and electrocoagulation in a single step (ECZ) using different metallic materials of carbon steel, aluminium alloy, and zinc as electrodes was investigated. The experiments were divided into two parts. In the first part, the nine experiments were carried out in an electrochemical batch-type reactor under different operating conditions planned according to Taguchi's L9 orthogonal array design. The electrode material (Fe, Al, Zn), initial pH (4, 6 and 8), the addition of NaCl electrolyte (0.5, 1, and 1.5 g/L), and addition of zeolite (15, 20 and 25 g/L) were chosen as controllable factors, and their impact on chemical oxygen demand (COD) and turbidity were studied. The results show that the highest removal for both COD and turbidity was obtained with the Al electrode at pH 4 and an electrolyte addition of 0.5 g/L NaCl and 15 g/L of zeolite. However, the pH and the addition of zeolite do not have the same effect on COD and turbidity removal. Microscopic analysis of the electrode surfaces shows pitting, general or uniform corrosion, and coverage with a layer of corrosion products depending on the experimental conditions. The order of anode consumption was Zn > Fe > Al. Cathode consumption was evident in the experiments with the Al electrode, while both cathode consumption and increase in cathode mass was observed in experiments with the Fe and Zn electrode. In the second part, the influence of the initial COD concentration of the compost leachates treatment by ECZ with aluminium alloy electrodes was studied under optimal condition previously defined. Higher initial COD concentrations result in steeper curves of COD removal during ECZ and to a higher settling rate.

The Electrochemical Reaction Kinetics during Synthetic Wastewater Treatment Using a Reactor with Boron-Doped Diamond Anode and Gas Diffusion Cathode

A system of boron-doped diamond (BDD) anode combined with a gas diffusion electrode (GDE) as a cathode is an attractive kind of electrolysis system to treat wastewater to remove organic pollutants. Depending on the operating parameters and water matrix, the kinetics of the electrochemical reaction must be defined to calculate the reaction rate constant, which enables designing the treatment reactor in a continuous process. In this work, synthetic wastewater simulating the vacuum toilet sewage on trains was treated via a BDD-GDE reactor, where the kinetics was presented as the abatement of chemical oxygen demand (COD) over time. By investigating three different initial COD concentrations (C0,1 ≈ 2 × C0,2 ≈ 4 × C0,3), the kinetics was presented and the observed reaction rate constant kobs. was derived at different current densities (20, 50, 100 mA/cm2). Accordingly, a mathematical model has derived kobs. as a function of the cell potential Ecell. Ranging from 1 × 10−5 to 7.4 × 10−5 s−1, the kobs. is readily calculated when Ecell varies in a range of 2.5–21 V. Furthermore, it was experimentally stated that the highest economic removal of COD was achieved at 20 mA/cm2 demanding the lowest specific charge (~7 Ah/gCOD) and acquiring the highest current efficiency (up to ~48%).

Adsorptive removal of organic pollutants from milk-processing industry effluents through chitosan-titanium dioxide nanoadsorbent-coated sand.

Milk-processing industry effluent (MPIE) poses severe problems for aquatic and environmental systems, especially in the South Asian region. Therefore, its treatment is of great interest. This study deals with the investigation of chitosan titanium dioxide nanoadsorbent (CTiO2) coated onto sand particles via calcination that are used to remove the emerging pollutants. The adsorptive properties of these developed adsorbents are compared with those of the nascent sand without coating as well as with the chitosan titanium dioxide nanoadsorbent coated sand (CTiO2-CS). Batch adsorption experiments were performed to investigate the percent reduction efficiency (%RE) of organic pollutants in terms of biological oxygen demand (BOD) and chemical oxygen demand (COD) from synthetic and real effluents. The maximum %RE of BOD (96.76) and COD (98.91) was achieved at 1.5M dose of CTiO2-CS, 120min of contact time, pH 6.5, an initial BOD concentration of 900mg/L, and an agitation speed of 400rpm. Similarly, the %RE of COD was found to be 86.75 for synthetic effluent and 90.97 for real effluent at initial COD concentrations of 8000mg/L. Pseudo-second-order and Langmuir models are found to be the best fits for BOD and COD adsorption. The diffusion model suggests that surface adsorption as well as intraparticle diffusion contribute to the actual adsorption process. Regeneration experiments were performed for four cycles, and CTiO2-CS was found to be the most regenerable adsorbent material. The performance of the adsorbent was compared with previous studies, and it was found to have excellent adsorption capacity. As a result, the developed filter bed could be used as a promising superadsorbent for the removal of organic load in MPIE.

Application of neural network approach for modelling COD reduction from real refinery effluent by electrocoagulation.

The present study aims to investigate the feasibility of implementing the electrocoagulation (EC) process to treat Algiers refinery effluent. The electrocoagulation was performed by using scrap aluminum plate electrodes in monopolar-parallel mode. Several parameters, namely current density, reaction time, the electrolyte dose, and the initial chemical oxygen demand (COD) concentration were studied. The maximum removal of COD achieved was found to be 78.55%. Operating conditions at which maximum COD removal efficiencies were achieved at current density 8 mA/cm2, electrolyte dose 1 g/L, with 360 mg/L of initial COD concentration at working time of 40 min. An artificial neural network (ANN) was also utilized to determine predicted responses using neural networks for the 4-10-1 arrangement. The responses predicted by ANN were in alignment with the experimental results. The values of the determination coefficient (R2 = 0.978) and the root mean square error (RMSE = 21.28) showed good prediction results between the model and experimental data. Hence, the ANN model as a predictive tool has a great capacity to estimate the effect of operational parameters on the electrocoagulation process.

Removal of Diclofenac Sodium from Wastewater in Microbial Fuel Cell by Anode Modified with MnCo2O4

Microbial fuel cell (MFC) with a modified anode is one of the new methods to increase MFC efficiency. This study synthesized an anode modified with cobalt manganese oxide (MnCo2O4@CF) on carbon felt (CF) by easy hydrothermal method and binder-free. Chemical oxygen demand (COD) was measured with and without diclofenac (DCF). According to SEM results, MnCo2O4 was uniformly dispersed on the anode electrode surface. Moreover, the maximum power density in COD (1000 mg/L), 48 h. condition without DCF (726 mA/m2) was 165 ± 0.012 mW/m2 and with DCF concentration of 20 mg/L, it was 308 ± 0.013 mW/m2 (992 mA/m2). In addition, in the presence of 10 mg/L DCF concentration, the maximum COD removal efficiency was 82% ± 1.93 at 48 h. COD removal efficiency without DCF was 94.67% ± 0.02 at 72 h. After 72 h, the maximum removal efficiency of COD and DCF in the carbon anode was 41% ± 1.15 and 9.5% ± 0.23, respectively. Moreover, the maximum DCF removal efficiency using a MnCo2O4 anode was 56% ± 0.55, at 48 h; the initial COD concentration was 500 mg/L, and the DCF concentration was 20 mg/L. This research showed that coating the anode with MnCo2O4 could lead to the increased growth of microorganisms on the surface of the anode, decreased load transfer resistance, increased power density, and more removal of COD and DCF. As a result, the performance of fuel cells with modified anode and removal of DCF increased compared to anode with CF-MFC. Thus, the performance of fuel cells with modified anode and removal of DCF increased compared to anode with CF-MFC.

Printing ink wastewater treatment using combined hydrodynamic cavitation and pH fixation.

Printing ink wastewater (PIW) carries a heavy load of pollutants, the composition of which makes treatment difficult, especially when trying to minimize the pollution load. According to the latter, the present study aims to investigate PIW treatment with different various methods and to determine the maximum color, COD (chemical oxygen demand) and TSS (total suspended solids) removal. First, hydrodynamic cavitation (HC) was tested and the effect of hydrogen peroxide dosage (0-10gL-1), and pH (3, 5, 8, 10) was examined concerning the removal of PIW initial COD concentrations 4000 and 8000mgL-1. Removal was high (more than 81%) only at pH 5 in HC reactor. The second method involved treatment with separate pH fixation of the undiluted PIW (COD 17000mgL-1, actual pH 8±0.2). This treatment, maximized removals, reaching reduction of the initial values more than 91%, at pH 5. Finally, PIW was treated with a combination of the above methods, leading to 93-97% removals for 8000mgL-1 PIW treatment and 97-99% for 17000mgL-1 PIW respectively. Process cost calculations showed that the latter method is an effective and affordable treatment method for PIW streams, while toxicity tests of the treated PIW showed substantial toxicity reduction.

Reciprocating subsurface-flow constructed wetlands: a microcosm treatability study.

Two batch-loaded microcosm treatability studies of eight days' duration (192 hours) were conducted concurrently from July 26 through August 3 in an environmentally controlled greenhouse at the Tennessee Valley Authority's (TVA) Constructed Wetlands Research Facility in Muscle Shoals, Alabama, USA. These, the first of five treatability studies, were conducted in batch-loaded wetland microcosms, with and without reciprocation. Reciprocation refers to the process of filling and draining paired wetland cells on a recurrent and timed basis to facilitate passive aeration of fixed microbial biofilms during the drain phase and oxygen depletion during the fill phase. The study was designed to simultaneously evaluate the influence of three treatment parameters with respect to removal dynamics of chemical oxygen demand (COD), total ammonia-nitrogen (TAN), nitrate-nitrogen, and orthophosphorus. The treatment parameters evaluated included four COD concentrations, two reciprocation cycle times, and the presence or absence of reed canary grass (Phalaris arundinacea), a plant with an anoxic rootzone. Temperature, pH, dissolved oxygen, electrical conductivity, redox potential, and evapotranspiration were also monitored. Results showed that treatments with reciprocation vs. no reciprocation provided significantly enhanced aerobic and anoxic treatment of wastewater and improved removal of COD and ammonium, irrespective of initial COD concentrations or planted vs. not planted with P. arundinacea. Treatments with P. arundinacea had less accumulation of nitrate nitrogen; less than 0.4 mg/L., while reciprocating treatments without P. arundinacea accumulated from 15-26 mg/L nitrate nitrogen over the 192-hour treatment period.

Supercritical water oxidation of coal pyrolysis wastewater: Effects of main operating parameters and reaction pathways of 2-(N-Morpholino)ethanesulfonic acid

Coal pyrolysis wastewater has high chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) contents, which seriously endanger human health and environment. In this work, supercritical water oxidation attempted to dispose coal pyrolysis wastewater. The results showed that the removal rates of COD and NH3-N were significantly improved with the increase of reaction temperature, oxidation coefficient, residence time and initial COD concentration. Residence time and reaction temperature played more important roles in organic matter degradation, and their extremum differences in orthogonal tests were 6.8% and 2.6%, respectively. The supercritical water oxidation processes of the N-containing compound 2-(N-Morpholino)ethanesulfonic acid in coal pyrolysis wastewater were speculated to mainly include two reaction pathways, in which large amounts of hexadecane, heptadecane and butyramide were found in the second pathway.

Heterogeneous Photodegradation for the Abatement of Recalcitrant COD in Synthetic Tanning Wastewater

Tannery wastewater is considered one of the most contaminated and problematic wastes since it consists of considerable amounts of organic and inorganic compounds. These contaminants result in high chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS). In this work, the heterogeneous photodegradation of recalcitrant COD in wastewater from the tanning industry was investigated, in particular the recalcitrant COD due to the presence of vegetable tannins extracted from mimosa and chestnut and from synthetic tannins based on 4,4′ dihydroxy phenyl sulfone. TiO2 Aeroxide P-25 was employed to study the photodegradation of model molecules in batch conditions under different parameters, namely initial concentration of COD, temperature, and catalyst dose. The maximum COD abatement reached was 60%. Additionally, preliminary kinetic investigation was conducted to derive the main kinetic parameters that can be useful for process scale-up. It was found to be independent of the temperature value but linearly dependent on both catalyst loading and the initial COD value.

COD inhibition alleviation and anammox granular sludge stability improvement by biochar addition

High chemical oxygen demand (COD) in anaerobic ammonium oxidation (anammox) reactors may destroy the structure or inhibite the activity of anammox granular sludge (AnGS). Herein, the effects of adding different biochars on the alleviation of COD inhibition, performance of anammox reactors in phases I (fed with an initial COD = 100 mg L−1) and II (= 150 mg L−1), as well as their effect on the properties of AnGS granules were investigated. Results showed that nitrogen removal in biochar-added reactors was superior to that in reactors without biochar (the control). AnGS with biochar addition outperformed the control in terms of stability (EPS and particle size distribution) as the initial COD concentration increased. In the reactors amended with litchi biochar and chinar biochar, the respective average TN removal efficiencies were 86.49% and 85.70% in phase Ⅰ as well as 86.54% and 85.51% in phase Ⅱ; the proportion of AnGS particles with a diameter of 1–3 mm reached a respective maximum of 80.97% and 73.74% (much higher than 67.69% in the control); and the AnGS granules had better stability with a little change in the protein (PN) to polysaccharide (PS) (PN/PS) values, the PN/PS values were 4.18 and 4.77 in phase Ⅰ as well as 4.21 and 4.70 in phase Ⅱ. Even at increasing COD concentrations, no significant change in the relative abundance of Planctomycetes was observed in all the biochar-containing reactors (P value over 0.9), and the relative abundance of anammox-related functional genes (hzs, hdh) was higher than that in the control.

Application of Electrocoagulation in Street Food Wastewater

Street food is commonly known as ready-to-eat and go foods and beverages, which is very famous in Thailand and other Asian countries. The street food daily generates high organic content and oily wastewater from washing and rinsing plates. The discharge of street food wastewater to public drains leads to a clogged drain line and unpleasant smell. In this work, an electrocoagulation (EC) system with monopolar aluminum (Al) electrodes was developed to treat two well-known street foods; Hainanese chicken rice (HC) and noodles and dumplings (ND). The results revealed that excellent chemical oxygen demand (COD) and fat, oil, and grease (FOG) removals were achieved under a specific operating condition (i.e., an electric current of 20 mA/cm2 and electrolytic time of 10 min). The initial COD of HC wastewater decreased from 40.6 g/L to 1.9 g/L, approximately 95%, whereas the FOG decreased from 310 mg/L to 50 mg/L, approximately 84%. The lower initial COD and FOG concentrations of ND wastewater obtained approximately 98% for COD removal and 86% for FOG removal; the effluent contained 0.5 g/L of COD and 25 mg/L of FOG. In addition, a relatively low Al concentration of 0.02–0.08 mg/L was observed in the effluents. The appropriate design factors together with ease of use and fast pollutants removal were significant advantages of this study; the EC system has potential to apply to on-site street food treatment.

Fe-zeolite catalyst for ozonation of pulp and paper wastewater for sustainable water resources

The pulp and paper industry consumes enormous quality of freshwater, leading to wastewater. It must be treated to remove pollutants, particularly residual dyestuffs, before releasing them to water bodies to avoid adverse environmental effects. The traditional wastewater treatment methods used for the pulp and paper industry are less efficient in colour and chemical oxygen demand (COD) removal. The current study is aimed at developing a novel catalyst for the catalytic ozonation of pulp and paper wastewater with better colour and COD removal for sustainable resources of clean water. The proposed catalyst is impregnated by iron on natural zeolites. Various parameters such as catalyst dose, pH, ozone dose, initial COD concentration, and reaction time are studied and optimized. The performance was evaluated by comparing the results with the single ozonation process (SOP) and catalytic ozonation process (COP). The highest COD and colour reduction efficiencies have been achieved, i.e., 71%, and 88% at a natural pH of 6.8. The proposed process achieved higher COD and colour efficiencies than the single ozonation process and catalytic ozonation process using raw zeolites. The improvement in efficiencies are 23% and 29% for SOP and 17% and 19% for COP, respectively. Hence, the results proposed the sustainability and applicability of COP to treat paper and pulp sector effluent.