Increase In Chemical Oxygen Demand Research Articles

Biomonitoring of Heavy Metal Toxicity in Freshwater Canals in Egypt Using Creeping Water Bugs (Ilyocoris cimicoides): Oxidative Stress, Histopathological, and Ultrastructural Investigations.

The abundance of metal pollutants in freshwater habitats poses serious threats to the survival and biodiversity of aquatic organisms and human beings. This study intends for the first time to assess the pernicious influences of heavy metals in Al Marioteya canal freshwater in Egypt, compared to Al Mansoureya canal as a reference site utilizing the creeping water bug (Ilyocoris cimicoides) as an ecotoxicological model. The elemental analysis of the water showed a significantly higher incidence of heavy metals, including cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb), in addition to the calcium (Ca) element than the World Health Organization's (WHO) permitted levels. The Ca element was measured in the water samples to determine whether exposure to heavy metals-induced oxidative stress engendered Ca deregulation in the midgut tissues of the creeping water bug. Remarkably, increased levels of these heavy metals were linked to an increase in chemical oxygen demand (COD) at the polluted site. Notably, the accumulation of these heavy metals in the midgut tissues resulted in a substantial reduction in antioxidant parameters, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and ascorbate peroxidase (APOX), along with a marked rise in malondialdehyde (MDA), cytochrome P450, and protein carbonyl levels. These results clearly indicate a noticeable disturbance in the antioxidant defense system due to uncontrollable reactive oxygen species (ROS). Notably, the results demonstrated that oxidative stress caused disturbances in Ca levels in the midgut tissue of I. cimicoides from polluted sites. Furthermore, the comet and flow cytometry analyses showed considerable proliferations of comet cells and apoptotic cells in midgut tissues, respectively, exhibiting prominent correlations, with pathophysiological deregulation. Interestingly, histopathological and ultrastructural examinations exposed noticeable anomalies in the midgut, Malpighian tubules, and ovarioles of I. cimicoides, emphasizing our findings. Overall, our findings emphasize the potential use of I. cimicoides as a bioindicator of heavy metal pollution in freshwater to improve sustainable water management in Egypt.

Enhanced removal of 1,2-dichloroethane by nanoscale calcium peroxide activation with Fe(III) coupled with different iron sulfides.

Fe(II) is of great importance in iron-based advanced oxidation processes. However, traditional methods to maintain Fe(II) concentration, such as the addition of chelating agents or reducing agents, may lead to an increase in chemical oxygen demand of secondary pollution. Therefore, in this study, iron sulfides, namely ferrous sulfide (FeS), pyrite (FeS2), and sulfidated nanoscale zero-valent iron (S-nZVI), were applied for not only the regeneration of Fe(II) but also the direct dissolution of Fe(II). Nanoscale calcium peroxide (nCaO2) was synthesized and used as the oxidant. The removal of 1,2-dichloroethane (1,2-DCA) were significantly promoted from 8.8 to 98.2, 79.2, and 80.8% with the aid of FeS, FeS2, and S-nZVI within 180 min, respectively. The dominant reactive oxygen species were demonstrated and their steady-state concentrations were quantified. Besides, the dechlorination of 1,2-DCA reached 90.4, 69.5, and 83.9% in nCaO2/Fe(III) systems coupled with FeS, FeS2, and S-nZVI, respectively. All three systems had high tolerance to the complex water conditions, of which FeS-enhanced nCaO2/Fe(III) system displayed the best performance, which could be recommended to put into practice for the remediation of 1,2-DCA contaminated groundwater.

Performance evaluation of a wet air oxidation reactor with external circulation for high-chemical oxygen demand wastewater treatment

The presence of high-concentration organic contaminants in wastewater poses considerable risks to the health of both humans and ecosystems. Wet air oxidation (WAO) is an attractive treatment option, but current dilution and retreatment processes do not align with economic and environmental principles. Here we report an external circulation wet oxidation treatment process that utilizes oxidizing liquids to reduce feed concentration. By coupling energy consumption model with computational fluid dynamics model, we explore the optimal parameters for an industrial external circulation reactor. A 90 kt/a external circulation wastewater treatment system has been established, achieving a 21.6% increase in chemical oxygen demand (COD) removal efficiency and a 34.8% reduction in energy consumption. These findings provide a promising pathway for the efficient, low-energy treatment of high-concentration organic wastewater while minimizing freshwater resource consumption.

Characterization of organic pollution in the Dianchi Caohai Lake at the transition between the dry and rainy seasons

Dianchi Caohai Lake is heavily polluted, and a significant increase in chemical oxygen demand (COD) occurs during the transition from the dry season to the rainy season. In order to analyze the cause of COD increase, the compositional characteristics of organic matter were investigated using three-dimensional fluorescence spectroscopy technology. The results showed that the most polluted area was located in the geographic center of the outer Caohai Lake, where COD reached 29 mg/L and was elevated by 52%, and protein-like and humus-like features were evident in the organic matter fractions. By measuring the characteristics of water in Caohai Lake, it was found that the fluorescence indexes were greater than 2.47, the biological index was distributed between 0.67 and 1.06, and the humification index was distributed between 1.81 and 3.12. It indicated that the lake had low humification and showed strong autochthonous source characteristics. The bloom outbreak was one of the main reasons for the elevated COD concentration. This study will provide theoretical support for the control of organic pollution in Dianchi Lake.

Sustainable utilization of anthraquinone-rich Rheum officinale as electron shuttle in microbial fuel cell: Strategy for stimulating monohydric phenols degradation and bioelectricity generation

In an aim to completely degrade refractory phenolic compounds for effective wastewater treatment, a sustainable strategy using anthraquinone-rich herbal plant contents as electron shuttles is presented. This study is the first attempt of treating four different chemical structures of monohydric phenols, while simultaneously generate low-carbon electricity in a microbial fuel cell. An electron shuttle-mediated strategy was introduced to investigate the effect of electron shuttle against the degradation of phenolic pollutants and bioelectricity generation, by employing Rheum officinale extract as electron shuttle. Results revealed that there was a two-fold increase in chemical oxygen demand (COD) removal, degradation extent of phenol and cresol isomers, output voltage and power density of MFC, compared to the mediator-free MFC system. The degradation of phenol yielded higher COD removal, degradation efficiency, output voltage and power generation over cresol isomers, with and without the application of electron shuttle. A complete removal of COD and phenol, with output voltage of 620.06 mV and power density of 252.49 mW/m2 were obtained. Phenol outperformed cresol isomers with regard to its sole activating hydroxy (−OH) group, lower dipole moment and higher electronic conductivity (8.53 mS/cm). Conversely, meta-cresol exhibited the lowest removal efficiency and power generation, ascribed to greater inductive influence of methyl group in meta position on the dissociation energy of the − OH group. Moreover, detection of the phenolic intermediates by gas chromatograph-mass spectrometer analysis was conducted, and detailed degradation pathways were presented.

Modelling the interaction between physico-chemical and bacteriological characteristics of oilfields produced water from a waste management facility

Bacteriological quality of oil and gas-related produced water is a function of the interaction of a complex set of factors, which invariably determine the ease with which this waste material may be treated effectively. Hitherto, only few studies have examined the interplay of these sets of factors on the incidence of coliform bacteria. The American Public Health Association (APHA) standard methods for the examination of wastewater were used to assess levels of 20 physicochemical and bacteriological parameters. Subsequently, negative binomial regression models were fitted to the coliform bacteria counts in the produced water data obtained from a waste treatment facility in Ghana. Zero-order relationships indicated that temperature, turbidity, BOD, COD, oil and grease, total phosphorus and nitrates were significant predictors of total coliform count unlike pH, conductivity, salinity, total dissolved solids and chloride. Except oil and grease, the relationships between incidence of coliform bacteria and BOD, COD and nitrates were not robust and disappeared in the organic, nutrients and demand model at the multivariate level. However, the significant relationships were restored when physical parameters were subsequently accounted for indicating that the latter suppressed the relationship in the organic, nutrients and demand model. pH was a significant predictor of coliform bacteria incidence only when physical and chemical parameters were taken into account in the multivariate model. Both sets of factors mediated the relationship between BOD and coliform bacteria incidence. Given the complex interactions between bacteriological and physicochemical quality of oilfields produced water, it is imperative to adopt a holistic and nuanced approach in managing waste emanating from oil and gas production. • There is a complex interactions between bacteriological and physicochemical quality of oilfields produced water • Among the physical parameters, an increase in temperature, turbidity and total suspended solids decrease the incidence of coliform bacteria in oilfields produced water • At the bivariate level, as biochemical oxygen demand increases, the incidence of coliform bacteria decreases. Similarly, an increase in chemical oxygen demand reduces the incidence of coliform bacteria • The multivariate analyses shows an inverse relationship between biochemical oxygen demand and incidence of coliform bacteria in oilfields produced water

High performance antibiofouling hollow fiber polyethersulfone nanocomposite membranes incorporated with novel surface-modified silver nanoparticles suitable for membrane bioreactor application

Surface-modified silver nanoparticles with amine, thiol, carboxyl, and the thiol-polyvinylpyrroldidone (PVP) functional groups were synthesized as functional filler for nanocomposite membranes for membrane bioreactor (MBR), with the aims to enhance antimicrobial effect of silver, while immobilizing silver nanoparticles inside the matrix of the membrane. Analyses by fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), and dynamic light scattering (DLS) proved successful surface modification for each type of nanoparticles, with average particle sizes of 69, 20, 33, and 34 nm for amine, carboxyl, thiol and thiol-PVP modified silver nanoparticles, respectively. Polyethersulfone (PES) based nanocomposite hollow fiber membranes showed different morphology and performance in ultrafiltration and MBR experiments. The surface modifications were able to immobilize silver nanoparticles inside the membrane by providing proper interactions between the nanoparticles and polymer, reducing silver release compared to the unmodified nanoparticles. Modified nanoparticles changed the phase inversion, resulting in different morphology and average pore size in the range of 7.6–28.0 nm. The surface-modified nanoparticles with enhanced antimicrobial activity improved antifouling properties of the nanocomposite membranes, leading to interesting MBR performance improvements, with 122 % increase of flux, 23 % increase of chemical oxygen demand (COD) removal and flux recovery by over 30 %.

Anthropogenic impact on long-term riverine CODMn, BOD, and nutrient flux variation in the Pearl River Delta

In the Pearl River Delta (PRD), population growth and economic development have steadily increased the anthropogenic nutrient discharge into coastal waters. In this study, we employed the observed concentration and model reproduced runoff to quantify the interannual variation and the long-term (1985–2021) trends in riverine chemical oxygen demand (CODMn), biochemical oxygen demand (BOD), and nutrient fluxes. The annual CODMn and BOD fluxes increased slightly between 1999 and 2021. In comparison, the mean annual dissolved inorganic nitrogen (DIN) fluxes of the four eastern outlets increased significantly from 2.05 × 105 t/a in 1985–1995 to 3.11 × 105 t/a in 1999–2011 and then to 3.91 × 105 t/a in 2014–2021. The outlets with the largest contributions to the CODMn, BOD, and DIN fluxes were Humen and Modaomen, which are both located near large cities. By calculating the CODMn fluxes upstream of the PRD, we found that the CODMn fluxes from downstream in the PRD increased faster than the fluxes from upstream. It follows that the increase in CODMn at outlets was mostly driven by the contributions of downstream major cities. In addition, the proportion of ammonia nitrogen flux in the DIN flux decreased from over 50 % to under 10 % at most outlets. This indicates that the toxicity of DIN fluxes has been mitigated. The DIN fluxes also showed a positive correlation with surface chlorophyll a and a negative correlation with bottom dissolved oxygen outside the Pearl River Estuary (PRE). This implies that the changes in phytoplankton growth and oxygen levels outside the PRE are closely linked to the variation in river-delivered nutrients, and the increasing riverine nutrient input may result in the expansion of intensified low-oxygen conditions outside the PRE.

Valorization of macroalgae digestate into aromatic rich bio-oil and lipid rich microalgal biomass for enhanced algal biorefinery performance

The valorization of macroalgae digestate as a secondary resource for high value chemicals and nutrients will promote the sustainability and circularity of anaerobic digestion based biorefinery. In this study, three digestates from A. nodosum C.linum and L. digitata were separated into liquid and solid fractions to investigate the production of high value added chemicals through pyrolysis using Pyrolysis Gas Chromatography Mass Spectroscopy (Py-GC/MS) while the filtered liquid fractions were tested as an alternative culture media to grow C. sorokiniana under mixotrophic conditions. The digestates showed different thermal degradation and an improvement of bio-oil profiles compared to the starter material. Pyrolyzates from raw macroalgae were characterized by a high anhydrosugar content in contrast to high aromatics observed in the case of their digestates. Toluene, benzofuran and vinylphenol, base chemicals for many industries, represented together 30–37% of the total chemicals produced during pyrolysis of the three macroalgae digestate. On the other hand, C. sorokiniana cultured on digestate-based media showed a higher lipid content with an increase in monounsaturated fatty acids and a lower polyunsaturated fatty acid content in comparison to microalgae grown in standard tris-acetate-phosphate media. Thus, the acyl composition was shifted in a direction more suitable for biodiesel production by this process. In addition, the increase of Chemical Oxygen Demand and Volatile Fatty Acids concentration in the digestate was found to reduce ammonium toxicity. Finally, 94% of Chemical Oxygen Demand and 83% of ammonium were removed by microalgae from the digestate-based media which will reduce the pollution risk of the biorefinery. Overall, the results indicate that using macroalgae solid digestates can generate improvements in the quality of products obtained by pyrolysis and the liquid digestate can positively influence microalgae growth and its products.

The short-term and long-term effects of industrial pollution on human health in China

The impact of environmental pollution on human health has become a consensus. Based on the provincial panel data of China from 2002 to 2017, this paper analyzes the impact of industrial wastes on human health. With respect to human health, average annual frequency of physician visits per capita (AAFPV) is used as a measure for the short-term human health; all-cause mortality is used to illustrate the long-term human health. The results show that in the short term, with the level of industrial smoke dust increasing every 1 percentage, AAFPV would increase by 0.24 percentage. This effect is significant in East China and West China. Central China is affected by industrial waste water, with a rate of increasing AAFPV by 0.12 percent for every 1 percent increase of chemical oxygen demand per unit area. In the long term, water pollution is the main influencing factor of all-cause mortality.

Performance evaluation of anoxic–oxic–anoxic processes in illuminated biofilm reactor (AOA-IBR) treating septic tank effluent

Abstract This study was conducted to evaluate the treatment performance of the anoxic–oxic–anoxic processes in illuminated biofilm reactor (AOA-IBR) in removing organics and nitrogen contained in septic tank effluent. The 27 L of the AOA-IBR was illuminated with red light-emitting diode (LED) lamps (peak wavelength of 635 nm, intensity of 100 μmol/(m2s)). Three types of biofilm media, namely ball ring®, plastic sheets and zeolite beads, were placed in the anoxic, oxic and anoxic zones, respectively, of the reactor to support the growth of microalgal–bacterial biofilm. The AOA-IBR was continuously fed with septic tank effluent and operated at hydraulic retention times (HRTs) of 24, 48 and 72 h. The experimental results found the increases in chemical oxygen demand (COD), total nitrogen (TN) and ammonia nitrogen (NH4-N) removal efficiencies with increasing HRTs in which the HRT of 72 h resulted in 78.6, 72.8 and 90.6% removals of COD, TN and NH4-N, respectively. The effluent quality of the AOA-IBR could meet the ISO 30500 effluent standards for Non-Sewered Sanitation Systems. The predominant microalgal biofilm species was observed to be Oscillatoria sp., while Proteobacteria was the predominant bacterial phylum found in the biofilm growing in the reactor. The above results suggested the applicability of the AOA-IBR in improving septic tank treatment performance which should result in better water pollution control.

Nanostructured boron-doped diamond electrode for degradation of the simulation wastewater of phenol

The applications of a boron-doped diamond (BDD) used in electrode application for toxic and refractory organic degradation have attracted much attention, and its efficiency is considered to be an important factor for its practical application. In this study, BDD thin films were prepared on Ti plates by double bias-assisted hot filament chemical vapor deposition (HFCVD) technique. A reactive ion etching process was introduced by a positive grid bias and a negative substrate bias which can generate an electric field in HFCVD system. Then a novel structure of BDD electrode with nanocone arrays was successfully etched from a flat diamond thin film by this system. The addition of the bias greatly improved the etching efficiency and promoted the formation of nanocones structures. The cyclic voltammograms (CV) test showed nanostructured BDD (NBDD) electrodes had excellent electrochemical performance almost the same as that of the electrodes with untreated surfaces. It had a large effective electroactive surface area (EASA), which was 31.0% greater than the unetched electrode. As a result, the NBDD electrode exhibited improved electrocatalytic performance as compared with the untreated one, i.e., an about 24.3% increase of chemical oxygen demand (COD) removal efficiency. Among them, the superiority of NBDD electrode was obvious in the initial stage due to its highest concentration in the initial stage. In addition, the NBDD electrode achieved higher average current efficiency (ACE) as compared with the untreated one.

Exploring the efficacy of powered guar gum (Cyamopsis tetragonoloba) seeds, duckweed (Spirodela polyrhiza), and Indian plum (Ziziphus mauritiana) leaves in urban wastewater treatment

The efficiency of aqueous extract of powdered guar gum seed (Cyamopsis tetragonoloba), duckweed fronds (Spirodela polyrhiza), and Indian plum leaves (Ziziphus mauritiana) was tested to remove nitrate, sulphate, phosphate, and chemical oxygen demand from urban wastewater in this study. Coagulants were applied in four different doses (1, 2, 3, and 5 mL/L) without adjusting the pH of it in wastewater treatment and changes in wastewater parameters were measured. The crude extract of guar gum seed, Indian plum leaves, and duckweed exhibited the removal activities 71.7–95.03% (nitrate), 78.3–95.9% (phosphate), and 83.1–99.6% (sulphate). Nitrate removal was highest (93.5%), followed by phosphate (83.4%) and sulphate (77.7%). The 3 mL/L dose of coagulant showed the best results of wastewater treatment, followed by 2 mL/L, 1 mL/L, and 5 mL/L. Chemical oxygen demand reduction was also in a good range (73.2–79.08%) with 3 mL/L dose for all studied coagulants. pH reduced significantly in all setups of wastewater spiked with plant coagulants. The chemical analysis of Fourier transforms infrared (FTIR) spectroscopy of aqueous extract and plant powder indicates the presence of functions groups like – OH, –COOH, –NH, CO, C–C R–CHO, CC–CO–OH, C–H, and R–NH2, in raw coagulants. Overall, results indicate the possible utility of guar gum seed, duckweed, and Indian plum leaf powder as low-cost natural materials for treatment of urban wastewater. However, few high doses of coagulants showed a slight increase in chemical oxygen demand in wastewater, which can be moderated by purifying the active compounds responsible for coagulation activities.

Effective biofilm control in a membrane biofilm reactor using a quenching bacterium (Rhodococcus sp. BH4).

The biofilm thickness in membrane biofilm reactors (MBfRs) is an important factor affecting system performance because excessive biofilm formation on the membrane surface inhibits gas diffusion to the interior of the biofilm, resulting in a significant reduction in the performance of contaminant removal. This study provides innovative insights into the control of biofilm thickness in O2 -based MBfRs by using the quorum quenching (QQ) method. The study was carried out in MBfRs operated at different gas pressures and hydraulic retention times (HRTs) using QQ beads containing Rhodococcus sp. BH4 at different amounts. The highest performance was observed inreactors operated with 0.21 ml QQ bead/cm2 membrane surface area, 12 HRTs and 1.40 atm. Overthis period, the performance increase in chemical oxygen demand (COD) removal was 25%, while the biofilm thickness on the membrane surface was determined to be250 μm. Moreover, acetate and equivalent oxygen flux results reached 6080 and 10 640 mg·m-2 ·d-1 maximum values, respectively. The extracellular polymeric substances of the biofilm decreased significantly with the increase of gas pressure and QQ beads amount. Polymerase chain reaction denaturing gradient gel electrophoresis results showed that the microbial community in the MBfR system changed depending on operating conditions and bead amount. The results showed that the QQ method was an effective method to control the biofilm thickness in MBfR and provideinsights for future research.

Poslovni proces poboljšanog tretmana otpadnih voda - smanjivanje rizika od zagađenja okoline

The Republic of Serbia is in the group of European countries, which have evident problems regarding the wastewater treatment. The main goal of the entire research is to point out the future of the process organization, as well as the correlation between the conduction of a concept of business processes and achieved performances management, based on a specific example of wastewater treatment. For the process of wastewater treatment, this paper will represent a as-IS model that was applied in the conditions of functional organizational structure, and a to-BE model, which was applied within the process orientation. For both of the models a review of the achieved parameters will be given, obtained by the application of the mentioned models. The given parameters indicate the presence of pollutants in wastewater after the conducted treatment process, with a description on how it reflected on the risk of environmental pollution. The innovated model of wastewater treatment achieves significantly better results, which is of great importance for environmental protection. Concrete evidence of the increase of chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS) removal with the use of these models is shown in this paper.

Towards enhanced chlorine control: Mathematical modeling for free chlorine kinetics during fresh-cut carrot, cabbage and lettuce washing

Abstract In this study, we developed a novel produce-specific mechanistic model to predict free chlorine (FC) dynamics during washing of disk-cut carrots, cut cabbage, and cut iceberg lettuce, in 3 L and 50–100 L tanks, and of shredded iceberg lettuce in 3200 L pilot-plant trials. Ranges for two key parameters: β (L mg−1 min−1) the apparent reaction rate constant of FC with produce constituents, and γ , the fraction of the increase of chemical oxygen demand (COD) contributing to the reaction, were determined at the 3 L scale. For disk carrots β ∈ [ 0.05 , 0.09 ] and γ ∈ [ 0.054 , 0.078 ] , for cut cabbage β ∈ [ 0.05 , 0.10 ] and γ ∈ [ 0.09 , 0.12 ] , and for cut iceberg lettuce β ∈ [ 0.03 , 0.06 ] and γ ∈ [ 0.07 , 0.14 ] . Taking values from these ranges the model was able to consistently predict experimental FC dynamics (decay and replenishment), indicating robustness of the apparent reaction rate constants across scales. Comparing sequential changes in COD with turbidity and total dissolved solids (TDS) relative to produce washing rates, our results also illustrate that turbidity and TDS may not be reliable predictors of FC decay rates across produce types and experimental scales. In concert with future experiments, these models could serve as important tools aimed at validating FC compliance within operational limits as well as guiding large-scale commercial experiments focused on improving chlorine management strategies relevant for industry.

Potential for anaerobic treatment of wastewater from pet bottle washing in a fluidized bed reactor

This study evaluated the potential of anaerobic treatment of wastewater from washing polyterephthalate ethylene (PET) bottles sent to recycling (WWPR) in a fluidized bed reactor. The reactor had a total volume of 2.16 L and was fed with the WWPR diluted in a nutritional medium operated with a hydraulic retention time (HRT) of 24 h and maintained at a temperature of 33 ± 2 °C. Coarse sand was used as a support material for the immobilization of biomass in the reactor. The potential of the anaerobic system was evaluated as a result of the progressive increase in chemical oxygen demand (COD) and anionic surfactants, both from the WWPR. The biomass was subjected to an immobilization and adaptation process over 10 days, and after this period, concentrations of anionic surfactants were added. The maximum COD load removed was 2.6 ± 0.43 kg/m³d, which represented a removal of 64 ± 8%. The maximum surfactant removal was 0.063 ± 0.001 kg/m³d for an initial concentration of 15 mg/L. The fluidized bed reactor was stable and robust in relation to the applied load of organic matter; however, surfactant removal was inhibited at initial concentrations above 30 mg/L.

Brine Recycling from Industrial Textile Wastewater Treated by Ozone. By-Products Accumulation. Part 1: Multi Recycling Loop

The “reactive” dyeing of textiles requires an application of low-molecular-weight salts (LMWS), such as NaCl or Na2SO4, as necessary auxiliary agents. LMWS acts only as a remediation factor and remains in the dyeing effluents constitute brine. The main goal of the presented study was to investigate the application of ozone technology for industrial textile wastewater highly polluted by LMWS. The study was divided into two parts. In Part 1, by-products accumulated during multi-recycling of the same wastewater was investigated. While Part 2 was devoted to the scaling up of ozonation process, Part 1 concerns the efficiency of textile wastewater ozonation carried out as a repeatable process. The sequence of wastewater treatment and textile dyeing was repeated four times in a closed loop using the same process water. Although the wastewater decolorization was efficient in the subsequent ozonation cycles, some adverse effects, such as an increase in chemical oxygen demand (COD) and self-buffering at pH 9.5–10.0, were suggested the accumulation of by-products. The preliminary detection of by-products by thin layer chromatography (TLC) revealed phenol and naphthol derivatives as the transformation products (TPs) of ozonation. Dyeing of cotton using purified wastewater (brine) resulted in very good DECMC color matching parameters (under 1.16), but only in the first recycling loop, and then the TPs affected the process.

High-rate activated sludge processes for municipal wastewater treatment: the effect of food waste addition and hydraulic limits of the system.

Conventional activated sludge (CAS) process is one of the most commonly applied processes for municipal wastewater treatment. However, it requires a high energy input and does not promote energy recovery. Currently, high-rate activated sludge (HRAS) process is gaining importance as a good option to reduce the energy demand of wastewater treatment and to capture organic matter for valorizing through anaerobic digestion (AD). Besides, food waste addition to wastewater can help to increase the organic matter content of wastewater and thus, energy recovery in AD. The objective of this study is to evaluate the applicability of co-treatment of municipal wastewater and food waste in a pilot-scale HRAS system as well as to test the minimal hydraulic retention times (HRTs) such as 60 and 30min. Food waste addition to the wastewater resulted in a 10% increase in chemical oxygen demand (COD)concentration of influent. In the following stages of the study, the pilot-scale system was operated with wastewater solely under the HRTs of 60 and 30min. With the decrease of HRT, particulate COD removal increased; however, soluble COD removal decreased. The results demonstrated that if the settling process is optimized, more particulate matter can be diverted to sludge stream.

Development of a mathematical model for the anaerobic digestion of antibiotic-contaminated wastewater

Anaerobic digestion has been investigated as a potential method for treating antibiotic-contaminated livestock wastewaters. Antibiotic removal is mainly associated with biodegradation and sludge adsorption. In environmental concentrations, i.e., from ngL−1 to a few hundred μgL−1, cometabolism is the most likely biodegradation pathway. The overall performance of anaerobic processes may be affected by the hydraulic retention time, and these processes are strongly related to the physical characteristics of the reactor and variations in influent chemical composition. The effects of these factors can be better understood using a mathematical model. Therefore, this paper aimed to develop a model to describe an anaerobic process to treat sulfamethazine (SMZ), which was divided into two stages of microorganism growth and substrate consumption. In addition, three hypotheses regarding sulfamethazine degradation, including substrate cometabolism related to both stages and an apparent enzymatic reaction, were evaluated. A long-term kinetics structure was added to the model to simulate the process of adaptation to each new operational condition. The results showed that sudden increases in chemical oxygen demand (COD) and hydraulic retention time (HRT) had the most significant negative impact on process performance. In addition, a sudden variation of 8μg of SMZ had a similar impact on the process as did 1000mg of filtered COD. Of the degradation hypotheses, the hypothesis related to organic acid consumption was more accurate than that related to hydrolysis; however, neither could account for the response to variations in HRT. The enzymatic approach resulted in a considerably more accurate representation of the influent flow rate variations than did the cometabolic hypotheses.