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While the effectiveness of Poly-Aluminum Chloride (PAC) coagulation for pollutant removal has been documented across various wastewater scenarios, its specific application in hospital wastewater (HWW) treatment to remove conventional pollutants and hazardous genetic pollutants has not been studied. The research compared three hospital wastewater treatment plants (HWTPs) to address a knowledge gap, including the PAC coagulation-sodium hypochlorite disinfection process (PAC-HWTP), the biological contact oxidation-precipitation-sodium hypochlorite process (BCO-HWTP), and a system using outdated equipment with PAC coagulation (ODE-PAC-HWTP). Effluent compliance with national discharge standards is assessed, with BCO-HWTP meeting standards for direct or indirect discharge into natural aquatic environments. ODE-PAC-HWTP exceeds pretreatment standards for COD and BOD5 concentrations. PAC-HWTP effluent largely adheres to national pretreatment standards, enabling release into municipal sewers for further treatment. Metagenomic analysis reveals that PAC-HWTP exhibits higher removal efficiencies for antibiotic resistance genes, metal resistance genes, mobile genetic elements, and pathogens compared to BCO-HWTP and ODE-PAC-HWTP, achieving average removal rates of 45.13%, 57.54%, 80.61%, and 72.17%, respectively. These results suggests that when discharging treated HWW into municipal sewers for further processing, the use of PAC coagulation process is more feasible and cost-effective compared to BCO technologies. The analysis emphasizes the urgent need to upgrade outdated equipment HWTPs. [Display omitted] • PAC-HWTP better removes genetic contaminants than BCO-HWTP, ODE-PAC-HWTP. • PAC-HWTP is cost-effective, meeting pretreatment norms for sewer release. • Urgent upgrades for outdated HWTPs needed to boost pollutant removal efficiency. • Metal resistance, mobile genetic elements, microbes determine antibiotic resistome. [ABSTRACT FROM AUTHOR]

The extreme pH, high color, and poor biodegradability of refractory wastewater have severe impacts on its biological treatment. To address this issue, an advanced Fe-Cu process with redox reaction and spontaneous coagulation was investigated and applied for pilot-scale (wastewater flow rate of 2000 m3·day−1) pretreatment of separately discharged acidic chemicals and alkaline dyeing wastewater. The advanced Fe-Cu process had five functions: (1) increasing the pH of chemical wastewater to 5.0 and above, with an influent pH of approximately 2.0; (2) transforming refractory organics of chemical wastewater with 10.0% chemical oxygen demand (COD) and 30.8% color removal, thereby enhancing the ratio of biological oxygen demand after five days (BOD 5) to COD (B/C) from 0.21 to 0.38; (3) neutralizing the pH of the pretreated chemical wastewater for coagulation application with alkaline dyeing wastewater to avoid adding alkaline chemical; (4) achieving average nascent Fe(II) concentrations of 925.6 mg∙L−1 using Fe-Cu internal electrolysis for mixed wastewater coagulation, resulting in an average of 70.3% color removal and 49.5% COD removal; (5) providing more efficient COD removal and B/C enhancement than FeSO 4 ∙7 H 2 O coagulation while avoiding secondary pollution. The green process offers an effective, easy-implemented solution for the pretreatment of separately discharged acidic and alkaline refractory wastewater. [Display omitted] • The advanced Fe-Cu process includes bimetal redox reaction and spontaneous coagulation. • The acid chemical and alkaline dyeing wastewater were simultaneously pretreated by pH adjustment and detoxification. • Compared with traditional pretreatment, this more low-cost process realizes a superior effect. • The pilot-scale study with wastewater flow rate of 2000 m3·day−1 was operated continuously for 24 weeks. • After the actual operation, this process is proved to be worthy of wide application. [ABSTRACT FROM AUTHOR]

To achieve simultaneous organics and ammonia (NH 4 +-N) removal toward leachate treatment, this study designed a composite anode (CA+), in which iron powders were attracted to RuO 2 -IrO 2 /Ti tube surface by an inserted magnet and utilized in electro-hybrid ozonation-coagulation (E-HOC). The E-HOC (CA+) resulted in higher chemical oxygen demand (COD) and NH 4 +-N removal with most content of CO 2 /H 2 O and gaseous N in product compared with E-HOC (Fe+), electrolysis ozonation and single ozonation. Reactive chlorine species (RCS) and coagulants were co-produced by compositing RuO 2 -IrO 2 /Ti and Fe powders, resulting in multiple reactions including electrocoagulation, ozone oxidation, synergistic between ozone and coagulants (SOC), electrolytic chloride and synergistic oxidation between active chlorine and ozone (SCO) occurred. Hydroxyl radical (•OH) generated through SOC reaction was promoted due the RCS generation in E-HOC. The interaction between •OH and Cl-/ClO- also contributed to enhanced Cl•/ClO• production. Consequently, synergy of chlorine, coagulants and ozone enhanced reactive species generation which contributed to favorable organics and NH 4 +-N removal. Enhanced •OH and RCS are also attributed to conversion of bio-refractory organics like polyphenol, polycyclic aromatics and S-containing to biodegradable ones, e.g., aliphatic compounds and CHO. This study provides an easily operating strategy for leachate treatment with high content organics and NH 4 +-N. [Display omitted] • Organics and NH 4 +-N were simultaneously converted mainly into CO 2 /H 2 O and gaseous N. • RCS were greatly produced by composite anode while ROS generating in the E-HOC. • Coagulant and chlorine were co-produced by compositing DSA tube and magnetic powder. • The synergy from chlorine, coagulant and ozone improved •OH and Cl•/ClO• generation. • Enhanced •OH and RCS emerging also worked on bio-refractory organics conversion. [ABSTRACT FROM AUTHOR]

Wastewater treatment plant (WWTP) is proposed to be a point source of microplastics (MPs) that enter aquatic environments. Here, we quantified and characterized MPs down to 20 µm at a tertiary WWTP in Korea over a 1-year period. All wastewater contained MPs during the monitoring period, with concentrations ranging from 114 ± 17–216 ± 65 particles/L for influent and from 0.26 ± 0.29–0.48 ± 0.11 particles/L for effluent. MP abundance in the influents showed significant seasonal differences whereas a seasonal trend was not observed for the effluents, indicating a stable treatment performance (approx. 99.8%) of the WWTP. Spatial surveys of MP distribution in the WWTP showed that most MPs were removed by coagulation-sedimentation and rapid sand filtration, but some MPs still remained in the final effluent to generate the potential annual load of 2.9 × 109 particles and 0.54 kg into the rivers. These findings highlight the importance of long-term monitoring and MP mass quantification that would promote more accurate estimation of the MP load from WWTPs. [Display omitted] • We estimated the annual MP discharged from tertiary WWTP in Korea. • MP abundance in the influents showed significant seasonal differences. • 99% of MPs were removed by clarification with coagulant and rapid sand filtration. • Rainfall had a significant effect on the MP mass loading. [ABSTRACT FROM AUTHOR]

Highlights: [•] Alum coagulation is an effective pre-treatment for UVC/H2O2 treatment of high salinity ROC. [•] Comparable DOC in samples but different coagulation success due to different nature of organics. [•] Comparable mineralization obtained for two different ROCs with UVC/H2O2 only treatment. [•] UVC/H2O2 treatment led to increased biodegradability with and without coagulation. [•] Significant reduction in energy consumption obtained after pre- and biological post-treatment. [Copyright &y& Elsevier]

Abstract: The treatment of hydrofluoric acid (HF) wastewater has been an important environmental issue in recent years due to the extensive use of hydrofluoric acid in the chemical and electronics industries, such as semiconductor manufacturers. Coagulation/precipitation and ion exchange technologies have been used to treat HF wastewater, but these conventional methods are ineffective in removing organics, salts, and fluorides, limiting its reuse for water quality and economic feasibility. One promising alternative is reverse osmosis (RO) after lime treatment. Based on pilot-scale experiment using real HF wastewater discharged from semiconductor facility, the spiral wound module equipped with polyamide membranes has shown excellent flux and chemical cleaning cycles. Our results suggest that coagulation/precipitation and spiral wound RO constitute the optimal combination to reuse HF wastewater. [Copyright &y& Elsevier]

Abstract: Acid mine drainage (AMD) in Yunfu iron sulfide mine contain Fe2+, Fe3+, and Al3+ up to 8000, 1700 and 1200mg/L, respectively. Phosphorus removal from synthetic wastewater with 10mg/L of total phosphorus (TP) concentration and second municipal effluent with 3.5–4.0mg/L of TP concentration were conducted with the AMD by jar tests. Dosage of the AMD and initial pH of water are the two most important parameters affecting the performance of phosphorus removal of the AMD. The optimal phosphorus removal efficiency and residual iron ions (TFe) concentration are 97.0% and 3.0mg/L, respectively, at 1.61 Fe/P molar ratio and pH 8.03 for synthetic wastewater, and 92.1% and 0.32mg/L, respectively, for second municipal effluent at 1.41 Fe/P molar ratio and pH 7.3. Resultant heavy metal concentration in effluents and precipitate was very low, and the risk of resultant heavy metal contamination was very small. The phosphorus removal performance of the AMD was much similar to that of ferric sulfate (FS) and polyferric sulfate (PFS), and better than that of FeSO4. And residual TFe concentration in treated water arising from utilization of the AMD was similar to that of FeSO4, and higher than that of FS and PFS. The AMD could be used as coagulant for phosphorus removal from wastewater directly due to the presence of Fe2+, Fe3+, and Al3+ largely. [Copyright &y& Elsevier]

Abstract: Fenton oxidation and coagulation–flocculation–sedimentation (CFS) were both effective in removing many organic constituents of the biotreated coking plant effluent before the final treatment in an activated carbon adsorber. Fenton oxidation broke down most persistent organic pollutants and complex cyanides present in the feed stream and caused the eventual biodegradation of the organic residues in the adsorber. The results of Fenton oxidation followed by adsorption and biodegradation in two biological activated carbon (BAC) adsorbers show that the combined treatment consistently produced a high quality final effluent of <50mg/L in CODCr and <0.5mg/L in total cyanide during the 70-d study without replacing any activated carbon. The BAC function of the adsorber substantially reduced the need for replacing activated carbon making the combined Fenton oxidation-BAC treatment process a cost effective treatment process to recycle the final effluent for many beneficial reuses while meeting the much more stringent discharge limits of the future. [Copyright &y& Elsevier]

Abstract: In this paper, a new composite inorganic–organic coagulant (PFC–EPI–DMA) was prepared by polyferric chloride (PFC) and epichlorohydrin–dimethylamine (EPI–DMA) under a given EPI–DMA/Fe and OH/Fe molar ratio. In comparison with PFC, the Fe (III) species and zeta potential of PFC–EPI–DMA were measured. Then their coagulation performance and coagulation kinetics for treating synthetic reactive dying wastewater were investigated. The results showed that the content of Fea and Feb in PFC–EPI–DMA and PFC coagulants decreased with increasing aging period. Compared to PFC, PFC–EPI–DMA had higher content of Fea but lower content of Feb and Fec. The zeta potentials of two coagulants decreased with increasing aging period within all tested pH range. For the treatment of reactive red 24, the color removal efficiency treated by PFC–EPI–DMA decreased, while that treated by PFC remained almost constant with increasing aging period. However, the color removal efficiencies of reactive blue 14 treated by two coagulants both decreased with increasing aging period. The results of floc aggregation process confirmed that with increasing aging period, the orders of floc growth rate, ratio and TWV treated by two coagulants were complicated. [Copyright &y& Elsevier]

Abstract: In this study, in situ formed Fe–Mn binary oxide (FMBO) was applied to treat a practical high-arsenic wastewater (5.81mg/L). FMBO exhibited a remarkable removal capacity towards both As(III) and As(V), achieving a removal efficiency over 99.5%. However, the FMBO-As particles could not be sufficiently separated by gravitational sedimentation due to their low sizes and negative charges, as being indicated from laser particle size and zeta-potential analysis. Thus, poly-aluminum chloride (PACl) was introduced as a coagulant to facilitate the solid–liquid separation, and it remarkably improved As removal efficiencies. Results of scanning electron microscope (SEM) revealed that PACl contributed to the formation of precipitates with larger sizes and compact surfaces, which was favorable to sedimentation. Moreover, residual soluble As was removed by PACl hydroxides. The optimum dosages of FMBO and PACl were determined to be 60mg/L and 80mg/L, respectively. Additionally, the secondary pollution was minimized in FMBO–PACl process. Based on these bench-scale results, a full-scale treatment process was proposed to successfully treat 40,000m3 of high-arsenic wastewater in a municipal wastewater treatment plant (MWWTP). The average As concentration in the effluent was about 0.015mg/L. FMBO–PACl process showed the advantages of high effectiveness, low cost, safety, and ease for operation. [ABSTRACT FROM AUTHOR]

Abstract: The need for more rational use of water also calls for more efficient usage. An example is the production of tissue paper, where large amounts of water are discharged into the drain because its turbidity does not allow for recirculation. While this is a serious problem, even worse is the fact that the quality of such wastewater makes it difficult not only to recirculate but also to discharge due to environmental law restrictions. In this paper, electrocoagulation is proposed as a suitable technology to meet standards of water discharge, and even better, as a treatment option for removal of turbidity. Since energy consumption has been a drawback for EC applications, relevant aspects that contribute to increase it such as cell voltage and current density have been reviewed. For this purpose a systematic micro-electrolysis study combined with macro-electrolysis experiments have provided evidence that shows it is possible to achieve a turbidity removal of 92% with an energy consumption of 0.68kWh/m3. Thus, the results presented in this paper support the use of EC to obtain water of acceptable quality for reuse in the tissue paper industry. [Copyright &y& Elsevier]

Abstract: A coupled coagulation–Fenton process was applied for the treatment of cosmetic industry effluents. In a first step, FeSO4 was used as coagulant and the non-precipitated Fe2+ remaining in dissolution was used as catalyst in the further Fenton process. In the coagulation process a huge decrease in total organic carbon (TOC) was achieved, but the high concentration of phenol derivatives was not diminished. The decrease in TOC in the coagulation step significantly reduces the amount of H2O2 required in the Fenton process for phenol depletion. The coupled process, using a H2O2 dose of only 2gl−1, reduced TOC and total phenol to values lower than 40 and 0.10mgl−1, respectively. The short reaction period (less than 15min) in TOC and phenol degradation bodes well for improving treatment in a continuous regime. The combination of both processes significantly reduced the ecotoxicity of raw effluent and markedly increased its biodegradability, thus allowing easier treatment by the conventional biological units in conventional sewage treatment plants (STPs). [Copyright &y& Elsevier]

Abstract: In this study, the Fenton process was found to be successful to treat landfill leachate rejected after reverses osmose treatment. Central composite design (CCD) and response surface method (RSM) were applied to evaluate and optimize the interactive effects of three operating variables, initial pH and dosages of H2O2 and Fe2+ on physical and oxidative performances of Fenton process. Six dependent parameters such as overall chemical oxygen demand (COD) removal, COD removals of oxidation and coagulation, mineralization, humic substances (HS) removal and sludge volume ratio (SVR) were either directly measured or calculated as responses. According to analysis of variances (ANOVA) results, six proposed models could be used to navigate the design space with high regression coefficient R 2 varied from 0.9489 to 0.9988. It was found that initial pH, H2O2 and Fe2+ dosage had significant effects on the overall COD removal, mineralization and HS removal due to their respective effects on the oxidation and coagulation removals. Synergies effect of oxidation and coagulation during Fenton process controlled the treatment. The visual search of overlaying critical response contours plot was demonstrated. The results indicated the optimum conditions to be 3.64 of initial pH, 100mM of Fe2+ and 240mM of H2O2 dosage, respectively. The experimental data and model predictions agreed well. The overall COD removal, COD removals of oxidation and coagulation, mineralization, HS removal and SVR of 71.81%, 46.22%, 25.80%, 63.81%, 91.53% and 3.50ml/mM were demonstrated. [Copyright &y& Elsevier]

Abstract: In this study, metal hydroxides generated during electrocoagulation (EC) were used to remove the chemical oxygen demand (COD) of oxide chemical mechanical polishing (oxide-CMP) wastewater from a semiconductor manufacturing plant by EC. Adsorption studies were conducted in a batch system for various current densities and temperatures. The COD concentration in the oxide-CMP wastewater was effectively removed and decreased by more than 90%, resulting in a final wastewater COD concentration that was below the Taiwan discharge standard (100mgL−1). Since the processed wastewater quality exceeded the direct discharge standard, the effluent could be considered for reuse. The adsorption kinetic studies showed that the EC process was best described using the pseudo-second-order kinetic model at the various current densities and temperatures. The experimental data were also tested against different adsorption isotherm models to describe the EC process. The Freundlich adsorption isotherm model predictions matched satisfactorily with the experimental observations. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the COD adsorption of oxide-CMP wastewater on metal hydroxides was feasible, spontaneous and endothermic in the temperature range of 288–318K. [Copyright &y& Elsevier]

Abstract: Organic matter contained in leachates appears to be a relevant indicator of waste evolution. Among the physico-chemical treatments applied to stabilize leachates, coagulation–flocculation is considered a classical process and electrocoagulation can be developed. Electrocoagulation tests were carried out in a laboratory pilot using aluminium plates and compared to classical coagulation–floculation with aluminium ions and to electrolysis alone. The leachate used in this study came from the landfill of Crezin (Limoges, France) and it presented low biodegradability and high concentration of macromolecules. To assess the efficiency of the chemical and electrochemical processes, we specifically studied Organic Matter (OM) by using two protocols: adsorption on XAD resins and fractionation by ultrafiltration. Biodegradable Dissolved Organic Carbon (BDOC) measurements were applied to the fractions extracted by XAD resins and were also used as an indicator of the efficiency of the treatments. Residual organic matter concentration was the same for the two processes but its composition appeared different after electrocoagulation: a higher percentage of small hydrophilic organic molecules which seemed to be less biodegradable than the initial organic matter was observed. [Copyright &y& Elsevier]

Abstract: In the present study, coagulation–flocculation was investigated as a pretreatment process for the treatment of purified terephthalic acid (PTA) wastewater. The effect of various inorganic and organic coagulants on the treatment of wastewater collected from flow equalization tank of an effluent treatment plant was studied. The settling and filtration characteristics of the sludge were also studied. The jar tests revealed that the wastewater was best treated when 3000mgl−1 of ferric chloride was dosed at pH 5.6. At optimum conditions, COD of the wastewater was reduced by 75.5%. The results of the gravity filtration of the treated wastewater showed that the addition of cationic polyacrylamide (175mgl−1) to ferric chloride coagulation improved the filtration characteristics and reduced the specific cake resistance. Scanning electron microscopy and energy dispersive spectroscopy studies were also conducted to know the sludge structure and composition, respectively. Thermal analysis of the sludge showed that the oxidation of the sludges in the present study is a three step process. However, with the addition of C-PAA to ferric chloride coagulation system, the oxidation was found to be a two step process. [Copyright &y& Elsevier]

Abstract: The leachate from Changshengqiao landfill (Chongqing, China) was characterized and submitted to a combined process of air stripping, Fenton, sequencing batch reactor (SBR), and coagulation. Optimum operating conditions for each process were identified. The performance of the treatment was assessed by monitoring the removal of organic matter (COD and BOD5) and ammonia nitrogen (NH3–N). It has been confirmed that air stripping (at pH 11.0 and aeration time 18h) effectively removed 96.6% of the ammonia. The Fenton process was investigated under optimum conditions (pH 3.0, FeSO4·7H2O of 20gl−1 and H2O2 of 20mll−1), COD removal of up to 60.8% was achieved. Biodegradability (BOD5/COD ratio) increased from 0.18 to 0.38. Thereafter the Fenton effluent was mixed with sewage at dilutions to a ratio of 1:3 before it was subjected to the SBR reactor; under the optimum aeration time of 20h, up to 82.8% BOD5 removal and 83.1% COD removal were achieved. The optimum coagulant (Fe2(SO4)3) was a dosage of 800mgl−1 at pH of 5.0, which reduced COD to an amount of 280mgl−1. These combined processes were successfully employed and very effectively decreased pollutant loading. [Copyright &y& Elsevier]

Abstract: The objective of the present study was to assess the electrocoagulation treatment of olive mill wastewater using an aluminum electrode. We have examined the effect of the following parameters on the removal of chemical oxygen demand (COD), polyphenols and dark color removal efficiency: Electrolysis time, Current density, Chloride concentration and Initial pH. The olive mill wastewater (OMW) – diluted 5 times – used in this study had 20.000mg/L chemical oxygen demand, 3.6mS/cm conductivity and acidic pH (4.2). It also contains considerable quantities of polyphenols (260mg/L). The evolution of the physico-chemical parameters during the treatment by electrocoagulation showed that under the following conditions: electrolysis time 15min, NaCl concentration 2g/L, initial pH 4.2 and current density 250A/m2, the discoloration of the olive mill wastewater, the reduction of the chemical oxygen demand and the reduction of polyphenols exceeded 70%, the electrodes consumption was 0.085kgAl/kgCODremoved and the specific energy consumed was 2.63kWh/kgCODremoved. Under these optimal experimental conditions, olive mill wastewater became non-toxic for Bacillus cereus. [Copyright &y& Elsevier]

Abstract: In this paper, the results of olive oil mill wastewater (OOMW) using physicochemical pre-treatment and Fenton and Fenton-like processes are presented. On the other hand, acute toxicities of raw, physicochemical pre-treated, and Fenton and Fenton-like oxidations applied samples of OOMW on activated sludge microorganisms using respiration inhibition test (ISO 8192) are presented. Chemical pre-treatment (acid cracking and coagulation–flocculation) positively affected the biodegradability and inhibition on activated sludge was considerably removed (>67% COD and >72% total-phenol removal). Fenton and Fenton-like processes showed high COD (>80%) and total-phenol (>85%) removal performance on evaluated effluents. Inhibitory effect of Fenton-like reagents applied samples on activated sludge mixture was considerably removed. In addition to the toxicity, total-phenol and COD removal efficiencies of applied processes, their associated operating costs were also determined in this paper. [Copyright &y& Elsevier]

Abstract: The present work deals with removal of hexavalent chromium from synthetic effluents in a batch stirred electrocoagulation cell with iron–aluminium electrode pair coupled with adsorption using granular activated carbon (GAC). Several working parameters such as pH, current density, adsorbent concentration and operating time were studied in an attempt to achieve higher removal capacity. Results obtained with synthetic wastewater revealed that most effective removal capacities of chromium (VI) could be achieved when the initial pH was near 8. The removal of chromium (VI) during electrocoagulation, is due to the combined effect of chemical precipitation, coprecipitation, sweep coagulation and adsorption. In addition, increasing current density in a range of 6.7–26.7mA/cm2 and operating time from 20 to 100min enhanced the treatment rate to reduce metal ion concentration below admissible legal levels. The addition of GAC as adsorbent resulted in remarkable increase in the removal rate of chromium at lower current densities and operating time, than the conventional electrocoagulation process. The method was found to be highly efficient and relatively fast compared to existing conventional techniques. [Copyright &y& Elsevier]

Abstract: This paper presents results of an experimental study of coagulation/flocculation process of wastewater generated from a polyvinyl chloride (PVC) plant. The wastewater contains fine chlorine-based solid materials (i.e. latex). Experiments were carried out using a model wastewater which is chemically identical to the actual plant but is more consistent. Inorganic ions (Al2(SO4)3, FeCl3 and CaCl2) and a water soluble commercial polyelectrolyte (PE) were added to the wastewater sample. Coagulation efficiency was determined by measuring both the turbidity of the supernatants and the relative settlement of the flocs in the jar test. It was found that aluminum and ferric ions were more efficient than calcium ions as coagulants. The addition of polyelectrolyte was found to improve substantially the coagulation/flocculation process. It was found that the (Al2(SO4)3) combined with the polyelectrolyte at certain pH and agitation speed gave the best results compared to calcium chloride or ferric chloride when combined with the same concentration of polyelectrolyte. Only 0.0375g of a solution of (0.5% Al2(SO4)3) was required to coagulate the model wastewater. Ferric chloride (2.5% FeCl3) combined with the polyelectrolyte, on the other hand, required 0.1g while the optimum turbidity is almost the same. As for calcium chloride (2.5% CaCl2) it was found to be the least effective. The coagulation/flocculation process was found to be dependent on both pH and the agitation speed. [Copyright &y& Elsevier]

An upflow packed bed reactor at laboratory scale has been operated for a continuous period of 5 months to investigate the technical feasibility of biological nitrate removal applied to the effluent of the coagulation–sedimentation wastewater of a metal-finishing industry. The reactor was fed with industrial wastewater in a five-fold dilution to reproduce the global spill in the factory (20/80, industrial wastewater/domestic wastewater) with a concentration of nitrate between 141 and 210gNO3-N/m3. Methanol was added as a carbon source for denitrification. Inlet flow rate was progressively increased from 9 to 40L/day (nitrogen input load from 45 to 250gNO3-N/(m3 h)). The highest observed denitrification rate was 135gNO3-N/(m3 h) at a nitrate load of 250gNO3-N/(m3 h), and removal efficiencies higher than 90% were obtained for loads up to 100gNO3-N/(m3 h). A mass relation between COD consumed and NO3-N removed around 3.31 was observed. Better results were achieved in a previous stage using tap water with nitrate added as a sole pollutant as a synthetic feed (critical load of 130gNO3-N/(m3 h) and denitrification rate of 200gNO3-N/(m3 h) at a nitrate load of 250gNO3-N/(m3 h)). This fact could indicate that the chemical composition of the industrial source hinders to some extent the performance of the biological process. Whatever case, results demonstrated the viability of the denitrification process for the global industrial wastewater. A simple model based on Monod kinetics for substrate consumption, and constant biomass concentration was applied to model the industrial wastewater treatment, and a reasonably good fitting was obtained. [Copyright &y& Elsevier]

In this study, the treatability of rose processing wastewater was investigated by using electrocoagulation (EC) methods compared to classical chemical (CC) and Fenton application (FA) processes. High chemical oxygen demand (COD) and dissolved solids contents were detected in the wastewater. Among these treatment applications, it was found that the EC unit is the most effective treatment technique for removal of both COD and turbidity. The removal efficiencies of COD and turbidity were as high as 79.8% and 81.4%, respectively, and the reaction time was 20min for EC methods. [Copyright &y& Elsevier]

This is the first part of a work on the chemistry of aluminium as coagulant in the treatment of highly polluted cork processing wastewater. The main aim of this first part was to determine the removal of organic matter – measured by reductions in chemical oxygen demand (COD), polyphenols (TP), and aromatic compounds (A) – that can be obtained using this physicochemical process. To this end, jar-test experiments were carried out to determine the optimal conditions for the process, in particular, the effective aluminium dosage, contamination level of wastewater, coagulant mixing time, stirring speed, and pH. The ranges of tested parameters for the coagulation process were: coagulant dose (33–166mgL−1 of Al3+), contamination of the wastewater (COD between 1060 and 3050mgO2 L−1), mixing time (5–30min), stirring speed (60–300rpm) and pH (4–11). The resulting removal capacities were in the ranges of 20–55% for COD, 28–89% for polyphenols, and 29–90% for aromatic compounds. The best results were obtained with a coagulant mixing time of 5min and a stirring speed of 300rpm. The optimal choices of pH and coagulant dose fundamentally depended on the contamination level of wastewater. [Copyright &y& Elsevier]

This is the second part of a master project on the chemistry of aluminum as coagulant in the treatment of highly polluted cork-process-wastewater. The main aim of this second part was to determine the influence of the operating conditions on the system's settleability parameters. It is well known that it is just as important to achieve good settleability parameters in the physico-chemical treatment of wastewaters as it is to attain a high level of decontamination. These parameters will determine the dimensions of the required equipment, and hence the costs of the installation. This part of the study therefore analyzes the influence of the different operating variables on the following settleability parameters: sediment volumetric percentage, settling velocity, sludge volume index and total suspended solids just after mixture with the coagulant. The ranges used for the experimental variables were: coagulant dose (83–166mgL−1 of Al3+), coagulation mixing time (5–30min), stirring rate (60–300rpm), contamination level of the wastewater (Wastewater II COD≈2000mg O2 L−1, Wastewater III COD≈3000mg O2 L−1), and pH (5–11). The optimal conditions found for the settling process were not the same as those that had been determined for the organic matter removal. In this case the optimal conditions were: coagulation mixing time (30min), stirring rate (60rpm), coagulant dose (83mgL−1 of Al3+) and pH (7–9). Finally, the Talmadge–Fitch method is used to apply the results to the design of a clarifier-thickener unit to treat 2m3 h−1 of wastewater. The required minimum area of the unit would be 4.11m2. [Copyright &y& Elsevier]

Coagulation–flocculation is a proven technique for the treatment of high suspended solids wastewater. In this study, the central composite face-centered design (CCFD) and response surface methodology (RSM) have been applied to optimize two most important operating variables: coagulant dosage and pH, in the coagulation–flocculation process of pulp and paper mill wastewater treatment. The treated wastewater with high total suspended solids (TSS) removal, low SVI (sludge volume index) and high water recovery are the main objectives to be achieved through the coagulation–flocculation process. The effect of interactions between coagulant dosage and pH on the TSS removal and SVI are significant, whereas there is no interaction between coagulant dosage and water recovery. Quadratic models have been developed for the response variables, i.e. TSS removal, SVI and water recovery based on the high coefficient of determination (R 2) value of >0.99 obtained from the analysis of variances (ANOVA). The optimum conditions for coagulant dosage and pH are 1045mgL−1 and 6.75, respectively, where 99% of TSS removal, SVI of 37mLg−1 and 82% of water recovery can be obtained. [Copyright &y& Elsevier]