Initial Effluent Research Articles

Integrated spectral based monitoring, optimization and control of the combined ozonation and powdered activated carbon adsorption process to remove organic micropollutants from secondary effluent

In this study, an innovative approach for the integrated monitoring, optimization and control of the combined ozonation (O3) and powdered activated carbon (PAC) adsorption process is introduced making use of spectral surrogates (UVA254 and EEM-PARAFAC components). The combined O3-PAC process is designed to remove organic micropollutants (µP) from secondary effluent. Therefore, the removal of 6 µP with varying ozone reactivity was systematically studied in both O3 and PAC as stand-alone systems and in the combined O3-PAC system. For the latter, adsorption experiments were performed with µP spiked into ozonated secondary effluent (sequential system) and with µP spiked into the initial secondary effluent before ozonation (integrated system). In accordance with Swiss standards, the goal was to achieve 80% atrazine removal (as a model O3 recalcitrant compound) at optimized O3 and PAC doses. An ozone dose ranging from 0.45 to 0.65 mg O3/mg DOC was more cost-effective in promoting subsequent PAC adsorption (less than 40%), particularly at low PAC doses (1-2 mg PAC/mg (initial (DOC))). The classical ideal adsorbed solution theory (IAST) model could not be used to predict the subsequent PAC dose after ozonation in the integrated system. Therefore, correlation models were established between (i) the reduction of spectral surrogates during both O3 and PAC dosing and µP removal, (ii) the reduction of spectral surrogates during ozonation and the related PAC dose of the subsequent adsorption process and (iii) between the reduction of spectral surrogates during ozonation and the integrated process. Based on these correlation models, an online spectral control strategy was developed and implemented. Finally, the optimal dosing strategy for 80% atrazine removal was determined as 0.5 mg O3/mg DOC and 1.4 mg PAC/mg (initial) DOC.

Carbon isotope fractionation during methane transport through tight sedimentary rocks: Phenomena, mechanisms, characterization, and implications

The phenomenon of carbon isotopic fractionation, induced by the transport of methane in tight sedimentary rocks through processes primarily involving diffusion and adsorption/desorption, is ubiquitous in nature and plays a significant role in numerous geological and geochemical systems. Consequently, understanding the mechanisms of transport-induced carbon isotopic fractionation both theoretically and experimentally is of considerable scientific importance. However, previous experimental studies have observed carbon isotope fractionation phenomena that are entirely distinct, and even exhibit opposing characteristics. At present, there is a lack of a convincing mechanistic explanation and valid numerical model for this discrepancy. Here, we performed gas transport experiments under different gas pressures (1–5 MPa) and confining pressures (10–20 MPa). The results show that methane carbon isotope fractionation during natural gas transport through shale is controlled by its pore structure and evolves regularly with increasing effective stress. Compared with the carbon isotopic composition of the source gas, the initial effluent methane is predominantly depleted in 13C, but occasionally exhibits 13C enrichment. The carbon isotopic composition of effluent methane converges to that of the source gas as mass transport reaches a steady state. The evolution patterns of the isotope fractionation curve, transitioning from the initial non-steady state to the final steady state, can be categorized into five distinct types. The combined effect of multi-level transport channels offers the most compelling mechanistic explanation for the observed evolution patterns and their interconversion. Numerical simulation studies demonstrate that existing models, including the Rayleigh model, the diffusion model, and the coupled diffusion-adsorption/desorption model, are unable to describe the observed complex isotope fractionation behavior. In contrast, the multi-scale multi-mechanism coupled model developed herein, incorporating diffusion and adsorption/desorption across multi-level transport channels, effectively reproduces all the observed fractionation patterns and supports the mechanistic rationale for the combined effect. Finally, the potential carbon isotopic fractionation resulting from natural gas transport in/through porous media and its geological implications are discussed in several hypothetical scenarios combining numerical simulations. These findings highlight the limitations of carbon isotopic parameters for determining the origin and maturity of natural gas, and underscore their potential in identifying greenhouse gas leaks and tracing sources.

Removal of Chromium (III) and Reduction in Toxicity in a Primary Tannery Effluent Using Two Floating Macrophytes.

Trivalent chromium (Cr(III)) is a contaminant with toxic activity. Its presence in waters and soils is usually related to industrial activities such as tanneries. The aim of this study was to compare the removal of Cr(III) in hydroponic solutions and tannery effluents using two floating macrophytes: Salvinia auriculata and Eichhornia crassipes. First, to determine the chromium removal capacity in solution and the bioaccumulation factor (BAF) in tissues of each plant, experiments were set up with contaminated solutions with Cr(III) concentrations of 2, 5, 10, 20, and 40 mg/L. Subsequently, both plant species were exposed to a primary tannery effluent contaminated with 12 mg/L of Cr(III) in order to study the removal capacity of organic and inorganic matter, as well as the acute toxicity in the water flea (Daphnia magna) and genotoxicity in zebrafish (Danio rerio). Tests carried out on nutrient solutions revealed that both plants have a high capacity for removing Cr(III) in solution. The BAF in tissues was higher in E. crassipes compared to S. auriculata. In the experiments with a tannery effluent, both species presented low nutrient and organic matter removal efficiency, but they showed good Cr(III) removal capacity, with average reduction values of 57% for S. auriculata and 54% for E. crassipes after 72 h of exposure. E. crassipes contributed most to the reduction in acute toxicity in D. magna, while S. auriculata did not show a similar effect. However, both plant species managed to reduce the genotoxicity marker in D. rerio when compared with the initial effluent and the control.

Chemically activated hydrochars as catalysts for the treatment of HTC liquor by catalytic wet air oxidation

Hydrothermal carbonization (HTC) is a highly efficient and valuable technology for treating wet solid wastes and producing solid carbon-based materials named hydrochar. In this work, a hydrochar coming from the HTC of an anaerobic digestion sludge of wastewater treatment plant was used to assess the influence of several activation agents, a base (KOH) and different chloride salts (FeCl3, ZnCl2, and CuCl2) with the exact molar quantities, to develop materials with enhanced surface area and potential inclusion of metal active species for application in wet air oxidation processes. The KOH as an activating agent increased the surface area of hydrochar up to ca. 1000 m2/g of BET surface area. The employment of CuCl2 and FeCl3 as activating agents allows Cu- and Fe-rich doped materials of remarkable surface areas with 49.1 and 42.5 wt% of each metal, respectively. Likewise, the catalytic behavior of the different synthesized carbon-based materials as metal-free and metal-doped catalysts was evaluated for the Catalytic Wet Air Oxidation (CWAO) of a HTC aqueous liquor from a HTC process of animal manure to produce a valuable stream of higher biochemical methane potential in anaerobic digestion. CWAO effluents increased the proportion of carboxylic acids as final by-products due to the oxidation of more complex organic compounds of the initial effluent (ketones, phenols, aromatics and olefins). The CWAO treatments improve the anaerobic digestion rate in biochemical methane potential tests, although the methane production was limited by the lower TOC concentration of the treated streams after CWAO. This research contributes to developing sustainable and efficient strategies for the HTC-liquor treatment, using its solid hydrochar as catalysts, closing the loop of a Circular Economy.

Changes in Microbiota Profile in the Proximal Remnant Intestine in Infants Undergoing Surgery Requiring Enterostomy.

Early-life gut dysbiosis has been associated with an increased risk of inflammatory, metabolic, and immune diseases later in life. Data on gut microbiota changes in infants undergoing intestinal surgery requiring enterostomy are scarce. This prospective cohort study examined the enterostomy effluent of 29 infants who underwent intestinal surgery due to congenital malformations of the gastrointestinal tract, necrotizing enterocolitis, or spontaneous intestinal perforation. Initial effluent samples were collected immediately after surgery and final effluent samples were collected three weeks later. Gut microbiota composition was analysed using real-time PCR and 16S rRNA gene sequencing. Three weeks after surgery, an increase in total bacteria number (+21%, p = 0.026), a decrease in Staphylococcus (-21%, p = 0.002) and Candida spp. (-16%, p = 0.045), and an increase in Lactobacillus (+3%, p = 0.045) and in less abundant genera belonging to the Enterobacteriales family were found. An increase in alpha diversity (Shannon's and Simpson's indexes) and significant alterations in beta diversity were observed. A correlation of necrotizing enterocolitis with higher Staphylococcus abundance and higher alpha diversity was also observed. H2-blockers and/or proton pump inhibitor therapy were positively correlated with a higher total bacteria number. In conclusion, these results suggest that positive changes occur in the gut microbiota profile of infants three weeks after intestinal surgery.

Mucor cells passively immobilized on rose waste phyto-biomass: An eco-friendly hybrid material for the biotreatment of reactive dye contamination

The immobilization of microbial cells on eco-friendly supports is a promising technique to obtain effectively immobilized biomaterials for the biotreatment of aquatic pollution. For the biosorption of reactive dye-contaminated water, a new immobilized biosorbent, rose waste/Mucor plumbeus cells (RWMPC) composite was designed by immobilizing the fungal cells on a process waste of the rose oil industry. Batch and continuous mode biosorption features of RWMPC under different pH, initial dye concentration, contact time, biomaterial dose, and effluent flow rate conditions were examined. Zeta potential measurements, FT-IR, and SEM analysis were used to determine the morphological features of the biomaterial and possible Reactive Blue 49 (RB49)-biomaterial interactions. Kinetic investigations revealed that Ho's pseudo-second-order kinetic model could offer the best data fitting for biosorption, while the Freudlich model best matched the equilibrium data. Immobilized biomaterial displayed a high biosorption capacity of 120.88mg g−1. With an appropriate flow rate and amount of RWMPC packed into the column, dynamic treatment tests demonstrated >90% biosorption efficiency. The breakthrough curve of the RWMPC column adequately fits Chu's simplistic model. Regeneration tests revealed that after ten consecutive cycles, the biosorption yield and recovery efficacy of RWMPC were >65 and 85%, respectively. Zeta potential tests, SEM micrographs, and FT-IR studies also verified the dye uptake. Using synthetic wastewater in a continuous system, RWMPC could remove >90% of RB49. Breakthrough and exhaustion points were identified, and the maximum exhaustion capacity value was computed as 127.6 mg g−1. The results might inspire a fresh approach to the problem of reactive dye contamination in waters.

Removal of micropollutants and ecotoxicity during combined biological activated carbon and ozone (BO3) treatment

Ozonation is a viable option to improve the removal of micropollutants (MPs) in wastewater treatment plants (WWTPs). Nevertheless, the application of ozonation is hindered by its high energy requirements and by the uncertainties regarding the formation of toxic transformation products in the process. Energy requirements of ozonation can be reduced with a pre-ozone treatment, such as a biological activated carbon (BAC) filter, that removes part of the effluent organic matter before ozonation. This study investigated a combination of BAC filtration followed by ozonation (the BO3 process) to remove MPs at low ozone doses and low energy input, and focused on the formation of toxic organic and inorganic products during ozonation. Effluent from a WWTP was collected, spiked with MPs (approximately 1 µg/L) and treated with the BO3 process. Different flowrates (0.25–4 L/h) and specific ozone doses (0.2–0.6 g O3/g TOC) were tested and MPs, ecotoxicity and bromate were analyzed. For ecotoxicity assessment, three in vivo (daphnia, algae and bacteria) and six in vitro CALUX assays (Era, GR, PAH, P53, PR, andNrf2 CALUX) were used.Results show that the combination of BAC filtration and ozonation has higher MP removal and higher ecotoxicity removal than only BAC filtration and only ozonation. The in vivo assays show a low ecotoxicity in the initial WWTP effluent samples and no clear trend with increasing ozone doses, while most of the in vitro assays show a decrease in ecotoxicity with increasing ozone dose. This suggests that for the tested bioassays, feed water and ozone doses, the overall ecotoxicity of the formed transformation products during ozonation was lower than the overall ecotoxicity of the parent compounds. In the experiments with bromide spiking, relevant formation of bromate was observed above specific ozone doses of approximately 0.4 O3/g TOC and more bromate was formed for the samples with BAC pre-treatment. This indirectly indicates the effectivity of the pre-treatment in removing organic matter and making ozone more available to react with other compounds (such as MPs, but also bromide), but also underlines the importance of controlling the ozone dose to be below the threshold to avoid formation of bromate. It was concluded that treatment of the tested WWTP effluent in the BO3 process at a specific ozone dose of 0.2 g O3/g TOC, results in high MP removal at limited energy input while no increase in ecotoxicity, nor formation of bromate was observed under this condition. This indicates that the hybrid BO3 process can be implemented to remove MPs and improve the ecological quality of this WWTP effluent with a lower energy demand than conventional MP removal processes such as standalone ozonation.

Effective utilization of discarded reverse osmosis post-carbon for adsorption of dyes from wastewater

In this study, the deployment of post Reverse Osmosis (RO)-carbon as a adsorbent for dye removal from water has been investigated. The post RO-carbon was thermally activated (RO900), and the material thus obtained exhibited high surface area viz. 753 m2/g. In the batch system, the efficient Methylene Blue (MB) and Methyl Orange (MO) removal was obtained by using 0.08 g and 0.13 g/50 mL adsorbent dosage respectively. Moreover, 420 min was the optimized equilibration time for both the dyes. The maximum adsorption capacities of RO900 for MB and MO dyes were 223.29 and 158.14 mg/g, respectively. The comparatively higher MB adsorption was attributed to the electrostatic attraction between adsorbent and MB. The thermodynamic findings revealed the process as spontaneous, endothermic, and accompanied by entropy increment. Additionally, simulated effluent was treated, and >99% dye removal efficiency was achieved. To mimic an industrial perspective, MB adsorption onto RO900 was also carried out in continuous mode. The initial dye concentration and effluent flow rate were among the process parameters that were optimized using the continuous mode of operation. Further, the experimental data of continuous mode was fitted with Clark, Yan, and Yoon-Nelson models. Py-GC/MS investigation revealed that dye-loaded adsorbents could be pyrolyzed to produce valuable chemicals. The cost and low toxicity associated benefits of discarded RO-carbon over other adsorbents reveal the significance of the present study.

Mixed infection of three nontuberculous mycobacteria species identified by metagenomic next-generation sequencing in a patient with peritoneal dialysis-associated peritonitis: a rare case report and literature review

BackgroundPeritonitis caused by nontuberculous mycobacteria (NTM) is an infrequent but important complication in patients undergoing peritoneal dialysis (PD). There has been no report of mixed infections with multiple NTM. Peritoneal dialysis-associated peritonitis (PDAP) caused by Mycobacterium abscessus is more common than that caused by M. smegmatis and M. goodii.Case presentationThis case concerns a patient with PDAP caused by gram-positive bacilli, which could not be identified at the species level in successive detections of initial peritoneal effluent. Later, M. smegmatis was detected with no sensitivity results in bacterial culture. However, metagenomic next-generation sequencing (mNGS) and first whole-genome sequences indicated that there were three species coexisting in the culture, including M. smegmatis (24,708 reads), M. abscessus (9224 reads), and M. goodii (8305 reads). This is the first case of PDAP with specific evidence that conventional detection methods isolated a poorly pathogenic NTM, whereas mNGS and first whole-genome sequences identified multiple NTM. Pathogenic bacteria might not be detected using conventional methods due to their lower abundance. This case report is the first description of mixed infections with more than two species of NTM during PDAP.ConclusionsPDAP caused by multiple NTM is rare, and the diagnosis is difficult. When NTM are isolated by conventional tests in patients who are suspected of infection, clinicians should be vigilant, and further tests should be performed to determine the presence of rare or even previously unknown bacteria, for which the quantity is relatively low, but the pathogenicity is high. The rare pathogen may be a primary agent in causing such complications.

Removal of nutrients from WWTP effluent by an algae-mussel trophic cascade

New treatment steps are needed to better remove nutrients from WWTP effluents to prevent further eutrophication of the receiving waterbodies. Algae can be used to remove nutrients from effluent, but the subsequent removal of the algae biomass remains a challenge. Employing the high filtration capacity of dreissenid mussels may offer an efficient tool to remove effluent grown algae. The aim of the present study was therefore to evaluate if an algae-mussel trophic cascade allows an efficient removal of both nutrients and effluent-cultured algae. To this end, we inoculated WWTP effluent with the alga Tetradesmus obliquus in a batch system and monitored algal growth and nutrient concentrations for 11 days. Subsequently, we fed this algal-effluent solution to Dreissena bugensis for 3 days, after which we determined the amount of remaining algae and produced (pseudo)faeces. The algae-mussel set-up was able to remove 99% of P and 99% of N from the initial effluent, and the combination of algae settlement and mussel filtration resulted in a 94% removal of suspended algae after only 24 h. A total of 67% of the algae were consumed by the mussels after 3 days. Most filtered algae were deposited as pseudofaeces. An even higher efficiency may be achieved by selecting algae with a high nutrient removal capacity, but also with a high palatability for the mussels. Nonetheless, this is the first research that shows that an algae-mussel cascade could already offer an efficient solution to reduce nutrient concentrations in WWTP effluent. This may reduce costs, energy consumption and coagulants use at WWTPs, and could offer an alternative for high-tech treatment techniques, which may be more suitable in countries lacking the infrastructure to build these high-tech treatment steps.

Role of Polymerase Chain Reaction in Peritoneal Dialysis Patients with Nonbacterial Peritonitis

Introduction: Culture-positive peritoneal dialysis (PD)-related peritonitis depends on proper sample collection and culture technique. Patients are investigated for fungal and tubercular peritonitis once the initial peritoneal effluent grows no bacteria and the patient is unresponsive to antimicrobials. However, they are diagnosed late in the course of illness and lead to irreversible peritoneal damage preventing reinsertion of PD catheter. The aim of the study was to assess the role of polymerase chain reaction (PCR) in diagnosis of fungal and Mycobacterium tuberculosis (MTB)-related peritonitis in patients on PD who presented with features of peritonitis. Materials and Methods: This was a prospective study and included patients who were diagnosed to have PD-related peritonitis as per the International Society of PD guidelines. All patients underwent panfungal and MTB complex (MTC) PCR of PD effluent on day 1 of admission. Results: Eighty-five patients with PD-related peritonitis were included in the study. In patients with no bacterial growth on PD fluid, panfungal PCR was positive in 22 (25.8%) patients and 2 (2.4%) patients had positive MTC PCR. Fungal organism could be isolated in 10 (11.7%) patients. Nine percent of patients with fungal peritonitis died. Conclusion: The use of PCR in patients with PD-related peritonitis will help in early diagnosis and management of fungal and tubercular peritonitis. It will also help in reducing mortality in these patients.

Effect of sulfide and hydroxide on the removal of heavy metal ions from hydrometallurgical zinc effluent

ABSTRACT Heavy metals removal from Specialized Industrial Park of Zinc of Zanjan effluent was tested using sulfide, hydroxide, and the combination precipitation. The initial effluent includes 200 ppm of zinc, 55 ppm of cadmium, 113 ppm of manganese, 0.85 ppm cobalt, 0.65 ppm nickel, 0.2 ppm iron, and 0.55 ppm lead. Sulfide precipitation using Na2S as a sulfide source is inefficient in the precipitation of manganese except in high concentrations of sulfide, while hydroxide precipitation using lime is not successful in cadmium removal. Combining these two methods in one and two steps is helpful in the precipitation and settling of all heavy metal ions. The optimum temperature, pH, sulfide concentration, and time were determined. The concentration of zinc, cadmium, manganese, cobalt, nickel, and iron were reduced to 0.1, 0.1, 0.14, 0.23, 0.19, and 0.16 ppm, while lead was not detected in the solution in optimum condition. The experiments were repeated for effluent with higher amounts of lead, iron, and nickel, and its success in efficient removing of these ions is also confirmed. Scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns were used to study morphologies and structures of precipitation. The concentration of Na2S plays a crucial role in removal efficiency. Excess sulfide causes the increment of ions such as manganese in the solution and decrements the efficiency discussed in this research. The lower use of lime, almost no excess sulfide ions in solution, fast kinetics, and precipitating of a wide range of metal ions are some advantages of this method.

Adsorption of lead, copper and zinc in a multi-metal aqueous solution by waste rubber tires for the design of single batch adsorber

Heavy metal pollution has emerged as one of the most serious environmental challenges facing the world today. The removal of heavy metals from the effluent is of special environmental concern because of their toxicity and persistence in nature. This study presents the suitability of activated carbon from waste rubber tire as a low-cost adsorbent for multiple adsorption of copper, lead and zinc from wastewater. The adsorbent removed heavy metal ions effectively from solution medium in the order of copper > lead > Zinc. The adsorption process was rapid with all metals reaching equilibrium within 120 min. The optimum pH for Lead was achieved at 5 and 6 for copper and Zinc. The removal of heavy metals was discovered to increase with adsorbent dosage and contact time and reduced with initial concentration. The adsorption of multiple heavy metals was modeled using Freundlich and Langmuir adsorption isotherms to assess the experimental findings. The equilibrium data better fitted to the Langmuir isotherm with regression coefficient (R2) of 0.9831, 0.9992 and 0.9953 for lead, copper and zinc respectively. The maximum adsorption capacities (Qmax) at equilibrium were 9.6805 mg/g, 12.4378 mg/g and 4.9950 mg/g for Lead, Copper and Zinc respectively. The adsorption kinetics indicated that pseudo-second-order kinetic model described well the sorption mechanism for multiple adsorption of heavy metals with R2 of more than 0.99 for all metal ions. An empirical model for predicting and designing of a single batch adsorber for 95 % multiple heavy metal ion removal at any given initial heavy metal ion concentration and effluent volume was further developed using activated carbon from waste rubber tires. Waste rubber tire Activated carbon demonstrated an ability for the treatment of wastewater containing these heavy metals in multimetal solutions.

Severe Hyponatremia and Continuous Renal Replacement Therapy: Safety and Effectiveness of Low-Sodium Dialysate

Rationale & ObjectiveIn patients with severe hyponatremia in the setting of acute kidney injury or end-stage kidney disease, continuous renal replacement therapy (CRRT) using standard-sodium (140 mEq/L) fluids may lead to excessively rapid correction of plasma sodium concentration. Use of dialysate and replacement fluids with reduced sodium concentrations can provide a controlled rate of correction of plasma sodium concentration.Study DesignWe performed a single-center retrospective analysis of the safety and effectiveness of this approach in patients with plasma sodium concentrations ≤ 126 mEq/L who underwent CRRT for 24 or more hours using low-sodium (119 or 126 mEq/L) dialysate and replacement fluids. Change in plasma sodium level was assessed at 24 and 48 hours after initiation of low-sodium CRRT and at the end of treatment.Setting & ParticipantsBetween January 2016 and June 2018, a total of 23 hyponatremic patients underwent continuous venovenous hemodiafiltration using low-sodium dialysate and replacement fluids; 4 patients were excluded from analysis because of CRRT duration less than <24 hours.ResultsThe 19 patients included in the study had a mean age of 56 years, 11 (58%) were men, and 15 (79%) were white. The initial mean plasma sodium level was 121 mEq/L and the initial CRRT effluent dose was 27 mL/kg/h. Only 2 (11%) patients had an increase in plasma sodium concentration > 6 mEq/L at 24 hours. Mean changes in plasma sodium levels at 24 and 48 hours and at the time of CRRT discontinuation were 3, 3, and 6 mEq/L, respectively. None of the patients developed osmotic demyelination syndrome.LimitationsKey limitations were small sample size and lack of a control group.ConclusionsUse of low-sodium dialysate and replacement fluids is a safe strategy for the prevention of overly rapid correction of plasma sodium levels in hyponatremic patients undergoing CRRT.

Dissolution-Desorption Dynamics of Strontium During Elution Following Evaporation: pH and Ionic Strength Effects

Radioactive strontium-90 (90Sr2+) is a fission byproduct of uranium and plutonium production, and therefore understanding its environmental fate is of particular importance for predicting the evolution of long-term risk from historical releases. The nonradioactive strontium cation, Sr2+, is a chemical analog for 90Sr2+ that is often used in studies designed to understand the environmental behaviors of 90Sr2+. The focus of this work was on understanding the dynamics of remobilization of strontium following evaporation to dryness in porous media. Evaporation is ubiquitous in the unsaturated zone, and has the potential to significantly impact the dynamics of transport by driving adsorption or precipitation on solid surfaces. For this work, a series of transport experiments were conducted examining the behavior of strontium over a range of pH values, ionic strengths, and concentrations. Saturated transport experiments were conducted, followed by experiments designed to examine the release and transport following evaporation to dryness. Results show increasing saturated retardation with increasing pH, decreasing ionic strength, and decreasing concentration, with the concentration exhibiting the strongest effect. Breakthrough curves at low concentrations were also found to be consistent with significant rate-limited desorption. Remobilization elution curves measured following evaporation to dryness exhibited the high initial effluent concentrations, exceeding the influent strontium concentration, most likely caused by the initial dissolution and accumulation of strontium by the advancing solution. Concentrations at later times were found to be largely consistent with the dynamics of saturated transport for the systems studied.

Kinetic and parametric studies of refinery effluent treatment in electrochemical reactor

Treatment of refinery effluent using an electrocoagulation reactor assisted with a natural coagulant, from Acacia tortilis, was investigated under controlled operating conditions. The influence of process variables – namely, type of electrode (copper (Cu), steel and aluminium (Al)), effluent pH (3·5–11·5), influent chemical oxygen (O2) demand (COD) of the effluent (605–2420 mg/l), coagulant dosage (1·0–6·0 g/l), voltage (15–45 V) and current (1·5–2·5 A) – on the COD removal efficiency was investigated. Among the different electrodes tested, the aluminium electrode performed well and could remove 74·2% at an equilibrium time of 90 min. Formation of the aluminium hydroxide (Al(OH)3) complex was identified as the working mechanism. The optimal conditions for better COD removal efficiency were identified as pH 5·5, coagulant dose of 4·0 g/l, voltage of 45 V and current of 2·5 A. The empirical relationship between the coagulant dose and the COD removal percentage was found to be exponential in nature. A pseudo-second-order kinetic model was found to represent the experimental data very well (coefficient of determination &gt; 0·900) and the kinetic constant (k2) was estimated as 0·20 × 10−3(g/mg)/min at an initial effluent COD of 2420 mg/l.

INFLUENCE OF POULTRY PROCESSING ENTERPRISSE WASTE WATER COMPOSITION ON A RELEVANT DOSE OF ALUMINI POLYOXYCHLORIDE COAGULANT

Wastewater from food processing enterprises are highly polluted. These include pollution of both organic origin and mineral inclusions and detergents. This fact necessitates their preliminary treatment before discharge to biological treatment plants. Most enterprises in the industry use reagent pressure flotation for cleaning.One of the most important aspects of high cleaning efficiency is the correct selection of reagents for treatment. However, due to the high heterogeneity of the wastewater of various enterprises, this task is becoming a quit difficult. So, the wrong selection of the coagulant and its dose can lead to the installation of inappropriate equipment at the enterprise. At the same time, the equipment of a reagent farm can be either insufficient productivity or overstated performance. Both of that will not allow to achieve the required treatment effect and will entail the discharge of untreated sewage into the water reservation.There are 6 operating enterprises which specializing in the production of poultry meat are considered in this paper. Considered enterprises operate on the same technology and produce identical products. At the same time, the wastewater of these enterprises is significantly different in composition. Concentration of suspended solids varies from 450 to 3500 mg/l, COD values from 1000 to 8400 mg/l, and BOD5 from 600 to 3000 mg/l. There are coagulation thresholds are determined for each of the studied enterprises. Obtained results are summarized in graphs depicting the effect of initial effluent concentrations on the coagulation threshold of each of the studied samples. Obtained results are summarized in graphs were constructed and curve equations that describe changes in the coagulant dose with a change in the concentration of contaminants in the initial effluent were proposed. Obtained equations can be used for predicting required dose of aluminum polyoxychloride coagulate for wastewater with known concentration of suspended solids, COD or BOD5. This information can be used at the design stages of new local treatment plants of poultry meat processing sewage, and during the technical re-equipment of treatment plants.

Treatment of olive processing wastewater by electrocoagulation: An effectiveness and economic assessment

In the present study, the technique of electrocoagulation (EC) followed by filtration was explored at the laboratory scale for the removal of organic compounds from olive debittering wastewater (ODW). Different parameters such as electrode type and distance as well as sample pH, current density, and electrolysis time were investigated in batch experiments with identical electrode geometries. Our results showed that highest pollutant removal efficiency and lowest operational cost were achieved using two Al electrodes at a distance of 1 cm apart with a sample pH of 4.0. Moreover, rises in the electrolysis time and current density (up to 60 min and 15 mA cm−2, respectively) led to improvements in the removal of chemical oxygen demand (COD), total polyphenolic compounds (TPC), and turbidity. Under optimized conditions, the removal of COD, TPC and turbidity reached 78.51, 90.44 and 97.92%, respectively; the values of 1.01 g m−3, 12.0 kWh cm−3 and 0.12 USD m−3 were calculated as the electrode consumption, electrical energy consumption and operating cost, respectively. Chromatography results revealed tyrosol and catechin as the main phenolic compounds present in both the initial effluent and the generated sludge.

Support vector regression (SVR)-based adsorption model for Ni (II) ions removal

Removal of heavy metals with adsorption using low-cost adsorbents has motivated many researchers across the world. In this work, support vector regression (SVR) model is developed for the prediction of the removal efficiency of Ni(II) ions using the waste from tea factory in terms of the independent parameters namely, particle size of adsorbent, pH of the solution, initial Ni (II) ion concentration, flow rate, effluent volume, bed depth and contact time. The SVR-based model is compared with the multiple linear regression (MLR) model using the statistical parameters. The correlation coefficient (R) and the average absolute relative error (AARE) values for the SVR-based has been obtained as 0.993 and 6.88% while those of MLR model they are 0.8393 and 74.54% respectively. The developed state-of-the-art SVR model, based on the structural risk minimization (SRM) principle, is found to predict the experimental values more accurately and is highly generalized.

Reduction of chloride emission by thickening of metallurgical wastewater

Purification and thickening tests of metallurgical industrial wastewater from sintering dust dechlorination unit were carried out. Raw wastewater of pH 6.95 consisted primarily of Zn2+, Pb2+, Cd2+, Tl+, Cl-, SO4-2, at concentrations of approx. 3,200; 60; 11,500; 100; 40,100 and 5,300 mg/dm3 respectively. The heavy metals removal consisted in chemical precipitation and sedimentation, firstly by sodium hydroxide, and secondly by sodium sulphide solutions resulting in average removal to levels below 1mg/dm3. Moreover, the experimental studies of evaporation process confirmed the possibility of chloride ions reducing, the distillate yield was approx. 80% of the initial effluent stream. The solid product obtained by two-stage evaporation was characterized by satisfactory purity. The results indicate maturity of the applied processes for wastewater treatment, allowing conditions close to zero-liquid-discharge to be achieved.