Single and Combined Application of Ozonation and Coagulation/Flocculation for Humic Acid Removal

Humic acids are often found in surface and ground waters as a result of organic matter decay. In this study, water samples containing 50 mgL^?1 humic acid were treated by conventional application of coagulation/flocculation technique. The results showed 70% ±10 turbidity, ≥82% ±10 UV₂₅₄ absorbance and 85% ±10 total organic carbon removal under pH 5–9 and above 5 mgL^?1 Fe³⁺ coagulant doses. Application of post-ozonation significantly increased the UV₂₅₄ absorbance and turbidity removal under low dose Fe³⁺ application. On the other hand ozonation prior to coagulation/flocculation process altered the structure of HA and caused no significant improvement in removal efficiencies.     

Regeneration of Mixed Solvent by Ion Exchange Resin: Selective Removal of Chloride and Sulfate

Abstract

The selective extraction of sulfate and chloride ions from mixed solvent solutions was investigated. The mixed solvents consisted of water and 50 to 100%‐w (salt‐free solvent) ethylene glycol. The extraction was measured for mixed solvent solutions containing only sulfate and chloride, and mixed solvent solutions saturated with trona (sodium sesquicarbonate, Na₂CO₃ · NaHCO₃ · 2H₂O(s). Three anion exchange resins, Dowex 1X8‐50, Dowex 21K‐Cl, and Dowex MSA‐1, were investigated for their chemical and physical resistance to the mixed solvent carbonate/bicarbonate solutions, for their swelling behavior in the different mixed solvents, and for their extraction efficiency for chloride and sulfate.

The loading of the ion exchangers was fitted to a Langmuir‐type sorption model. While the extraction from trona‐free mixed solvents was well reproduced, the loading of the ion exchangers with chloride and sulfate from trona‐saturated mixed solvent solutions did not fit the sorption model. It appears, rather, that under these conditions chloride and sulfate are “salted out” of the bulk solution and driven into the ion exchangers.     

Effects of Ozonation on Molecular Weight Distribution of Humic Substances and Coagulation Processes – A Case Study: The Úzquiza Reservoir Water

In this article the influence of preozonation on the effectiveness of NOM removal via coagulation processes will be studied (focusing on the influence of the calcium hardness) as well as changes in MW (molecular weight) distribution of humic substances caused by ozonation. Additionally, THMFP removal in both ozonation and preozonation-coagulation processes is assessed. Three different types of water have been used in this study: a natural water from the Úzquiza Reservoir (Burgos, Spain), a synthetic water prepared using natural fulvic acids extracted from the Úzquiza Reservoir and a synthetic water prepared using a commercially supplied humic acid. Molecular weights of humic substances were determined using high-performance size exclusion chromatography (HPSEC); average molecular weights calculated for the unozonated humic substances are 4500 Da for the commercial humic acids and 1000 Da for the natural fulvic acids extracted from the Úzquiza Reservoir. Preozonation shifted the molecular weight distribution of humic substances (both humic and fulvic acids) towards lower average molecular weight values. For the natural water from the Úzquiza Reservoir (with low levels of calcium hardness and hydrophobic fraction (humic substances) being the main fraction of NOM), preozonation has a negative effect on the effectiveness of the coagulation process for NOM removal: the percentages of TOC removal via coagulation decrease with increasing ozone dosage; the maximum TOC removal (33%) is achieved for the unozonated water. Also for this water, ozonation reduced 5–25% of THMFP with ozone doses varying from 0.25 to 2.5 mg O₃/L. A preferential THMFP removal, that is to say, higher reduction in THMFP (43%) relative to TOC (28%) is achieved by the coagulation-flocculation process; this also occurs when preozonation is used, independently of ozone dosage.     

A Comparative Approach to the Application of a Physico‐Chemical and Advanced Oxidation Combined System to Natural Water Samples

Abstract

Natural organic matter removal (NOM) efficiencies of samples from three major drinking water sources (Elmali, Omerli, and Buyukcekmece) of Istanbul were compared using different treatment systems. Enhanced coagulation as a physico‐chemical method was applied using ferric chloride and aluminum sulphate as the coagulating agents. Moreover, the application of enhanced coagulation in combination with photocatalytic oxidation using TiO₂ was investigated. The efficiency of NOM removal relevant to each treatment step was assessed through DOC removal, UV₂₅₄ removal, and fluorescence measurements.

Irrespective of the treatment applied as enhanced coagulation, photocatalytic oxidation or their combinations, the highest removal efficiency was determined for Elmali followed by Omerli and Buyukcekmece samples both in terms of DOC and UV₂₅₄. Enhanced alum coagulation leads to significant variation in DOC removals as 44%, 28% and 26% for Elmali, Omerli, and Buyukcekmece water samples, respectively. Upon application of ferric chloride as the coagulant, the DOC removals achieved were found to be slightly higher as compared to alum. Moreover, the combined treatment incorporating photocatalytic oxidation subsequent to alum coagulation leads to 36%, 37%, and 50% of DOC removal for Omerli, Buyukcekmece, and Elmali respectively. The improvement of removal efficiencies in combined treatment systems were scrutinized with an emphasis on induced water properties as supported by the specific fluorescence intensities of the samples.     

Effects of O3, O3/H2O2 and Coagulation on Natural Organic Matter and Arsenic Removal from Typical Northern Serbia Source Water

The objectives of this study were to investigate the effects of ozone and the O₃/H₂O₂ process on FeCl₃ coagulation efficiency for the removal of the high content of natural organic matter (NOM) and arsenic (As) from groundwater (DOC = 9.27 ± 0.92 mg/L; 51.7 ± 16.4 µg As/L). Arsenic and NOM removal mechanisms during coagulation/flocculation are well investigated. However, data concerning arsenic removal in the presence of NOM, which is the subject of this article, are still insufficient. Laboratory and pilot plant test results have shown that the competition of NOM and As for adsorption sites on the coagulant surface have great influence on coagulation/flocculation efficiency for their removal. With both oxidation pre-treatments, arsenic content after the coagulation process was less than 2.0 µg/L in treated water. Application of ozone has a lower influence on coagulation efficacy in terms of DOC reduction, compared to the O₃/H₂O₂ process with the same ozone dose.     

Removal of Heavy Metals from Aqueous Solutions by Precipitation-Filtration Using Novel Organo-Phosphorus Ligands

Abstract

An organophosphorus mixture of sodium mono- and di-(n-hexa-decyl) phosphinate was synthesized and purified, and then used as a ligand to remove heavy metals by precipitation from aqueous nitrate, chloride, and sulfate solutions. The new ligand offers more advantages over the previously studied sodium dioctyl and dodecyl phosphinates. The sodium form of the mono- and di-(n-hexa-decyl) phosphinate has a much lower solubility in water, which contributed to much lower back contamination and much lower loss of the reagent, even when excess amount of ligand was employed. Moreover, an excess amount of the ligand did not alter the filtration characteristics of the resultant precipitate. The heavy metals: lead, cadmium, mercury, cobalt, and nickel were precipitated with the sodium mono- and di-(n-hexa-decyl) phosphinate, NaL, in the form of Pb L _2(s), Cd L _2(s), Hg L _2(s), Co L _2(s), and Ni L _2(s). In the absence of free acid in the feed, a maximum removal of each metal corresponded to the stoichiometric ratio. The residual concentrations of each of the metals at the optimum conditions were measured for the different media and found to be lower than 10 ppb, lower than the acceptable levels for most regions. Lead, as a model heavy metal, was studied in more detail. Adding an acid to the feed solution reduced the removal of lead as some of the phosphinate ligand was converted to the acid form. The presence of chloride and sulfate in the feed solution; up to mole ratios to lead of 5000, and of calcium in the feed solution; up to mole ratio to lead of 200, had no effect on the removal of lead. The ligand was more selective to lead than the other four metals, and the selectivity was in the order Pb > Cd > Co & Ni > Hg. The ligand was regenerated up to 99.99% and the metals were recovered in 100 times more concentrated aqueous solutions.     

水合MnO_2强化FeCl_3共沉降去除水中微量Cd(Ⅱ)

采用烧杯混凝实验,分别以实验室配水和松花江水为本底,研究了水合二氧化锰强化三氯化铁共沉降去除水中微量镉的效能。详细探讨了影响水合二氧化锰强化三氯化铁共沉降去除水中微量镉的主要因素。结果表明:两种水质条件下,水合二氧化锰均可强化FeCl3混凝去除水中的微量镉,镉的去除率明显高于单纯FeCl3混凝。水体pH值、浊度、腐殖酸等水质参数对于水合二氧化锰强化三氯化铁共沉降去除水中微量镉的效能有不同程度的影响。其中水体pH值对水合二氧化锰强化三氯化铁共沉降去除水中微量镉的影响十分显著,Cd(Ⅱ)的去除效果随着水体pH增加显著升高。     

Effect of Metallic Coagulant Agents on Oily Wastewater Treatment Performance using Mullite Ceramic MF Membranes

In this paper, the effects of in-line coagulation on permeation flux (PF), fouling resistance (FR), and total organic compound (TOC) rejection (R) of synthesized mullite ceramic membranes during treatment of oily wastewater in coagulation – MF hybrid process were investigated. Four coagulant ((ferrous chloride (FeCl₂.4H₂O), ferrous sulphate (FeSO₄.7H₂O), aluminum chloride (AlCl₃.6H₂O) and aluminum sulphate (Al₂(SO₄)₃.18H₂O)) plus equal concentration of lime in the form of calcium hydroxide (Ca(OH)₂) were evaluated in the coagulation – MF hybrid process at different concentrations (0 ppm, 25 ppm, 50 ppm, and 100 ppm). The results showed that coagulation can affect the membrane filtration by changing characteristics of the oil droplets. Coagulant agents improve the membrane performance at low dosage (25 ppm) for aluminum chloride and mean dosage (50 ppm) for ferrous chloride, ferrous sulphate, and aluminum sulphate. At the best conditions (50 ppm ferrous sulphate), PF increased from 2.22 × 10^?5 to 2.76 × 10^?5 (m³/m² s), FR decreased from 4.2 × 10¹² to 5.55 × 10¹¹ (m^?1), and R increased from 93.8% to 97.1%.     

Removal of Nitrate from Water by Adsorption onto Zinc Chloride Treated Activated Carbon

Abstract

Adsorption study with untreated and zinc chloride (ZnCl₂) treated coconut granular activated carbon (GAC) for nitrate removal from water has been carried out. Untreated coconut GAC was treated with ZnCl₂ and carbonized. The optimal conditions were selected by studying the influence of process variables such as chemical ratio and activation temperature. Experimental results reveal that chemical weight ratio of 200% and temperature of 500°C was found to be optimum for the maximum removal of nitrate from water. Both untreated and ZnCl₂ treated coconut GACs were characterized by scanning electron microscopy (SEM), Brunauer Emmett Teller (BET) N₂‐gas adsorption, surface area and Energy Dispersive X‐Ray (EDX) analysis. The comparison between untreated and ZnCl₂ treated GAC indicates that treatment with ZnCl₂ has significantly improved the adsorption efficacy of untreated GAC. The adsorption capacity of untreated and ZnCl₂ treated coconut GACs were found 1.7 and 10.2 mg/g, respectively. The adsorption of nitrate on ZnCl₂ treated coconut GAC was studied as a function of contact time, initial concentration of nitrate anion, temperature, and pH by batch mode adsorption experiments. The kinetic study reveals that equilibrium was achieved within one hour. The adsorption data conform best fit to the Langmuir isotherm. Kinetic study results reveal that present adsorption system followed a pseudo‐second‐order kinetics with pore‐diffusion‐controlled. Results of the present study recommend that the adsorption process using ZnCl₂ treated coconut GAC might be a promising innovative technology in future for nitrates removal from drinking water.     

Bilge Water Treatment in an Upflow Electrochemical Reactor using Pt Anode

Bilge water treatment was studied in an upflow electrochemical reactor (UECR) in order to design a compact onboard wastewater treatment system. The influence of retention time on the removal efficiencies of chemical oxygen demand (COD) and turbidity were analyzed, and optimized using response surface methodology (RSM) for maximizing the removal efficiencies. The best operating performance was obtained at 390 min retention time and 480 min reaction time for cost effective analysis with the composition of 100% bilge water (COD_o = 3080 mg/L) and 50/50% seawater/fresh water, 12.8 mA/cm² current density, and 32°C reaction temperature. Under response surface optimized conditions, the responses were estimated as; 90% COD removal, 97% turbidity removal, outlet pH value of 8.1, mass transfer coefficient of 0.494 × 10^?5 m/s, and mean energy consumption of 44.8 kWh/kg COD removed.     

Hybrid polyvinyl alcohol/polyvinyl chloride nanocomposites reinforced with graphene-carbon nanotube for acid red environmental treatments

ABSTRACT

Hybrid polyvinyl alcohol and polyvinyl chloride/graphene and carbon nanotube nanocomposites PVA–PVC/Gr–CNTs_a-e were successfully synthesized by a solution-casting method. Mixed Gr–CNTs ratio (50%:50%) was prepared in 2, 5, 10, 15, and 20 wt% and added to the host polymers (PVA/PVC). The characterization tools for the fabricated nanocomposites show homogenous interaction between the fillers and PVA/PVC polymer matrix. A significant improvement in the thermal properties of the (PVA/PVC) matrix was observed by adding mixed fillers, even at low loadings of mixed Gr–CNTs on to the matrix. Scanning electron microscopy and transmission electron microscopy images of the prepared composites show a good dispersion of PVA–PVC and mixed Gr–CNTs and present core-shell morphology. Impressive improvement in the percentage of acid red removal using PVA–PVC/Gr–CNTs_a–e was achieved and improved with time, solution temperature, and composites mass. The process of removing acid red was described kinetically and thermodynamically. The pseudo-second-order kinetic model is the most appropriate kinetic model to describe the adsorption of acid red by PVA–PVC and PVA–PVC/Gr–CNTs_d nanocomposites from an aqueous solution. Our results offer a facile method for the removal of acid red from three types of water: red sea, tap water, and distilled water.     

混凝对垃圾渗滤液中腐殖质的去除特性

通过分别投加混凝剂聚合氯化铝(PAC)、聚合硫酸铁(PFS)和聚合氯化铝铁(PAFC)对垃圾渗滤液进行混凝沉淀处理,考察了3种混凝剂对渗滤液中TOC、CODCr和UV254的去除效果,并且根据单因素试验确定出PAC为最佳混凝剂,最佳投药量为6g/L.对渗滤液腐殖质分离方法进行了简化,并对经3种混凝剂处理后水样内的腐殖酸...     

A comparative study of electrocoagulation and electro-Fenton for food industry wastewater treatment: Multiple response optimization and cost analysis

ABSTRACT

In this study, response surface methodology was applied for food wastewater by electrocoagulation (EC) and electro-Fenton (EF) processes. The optimum conditions for the chemical oxygen demand (COD) removal were found to be 21.36 min, pH 10 and 86 mA/cm² in EC, whereas 27.11 min, pH 2.38, 86 mA/cm² and H₂O₂/COD:2 in EF process. COD removal efficiencies were determined to be 29.4% for EC and 59.1% for EF processes and higher than 99% total suspended solids removal efficiencies were achieved. It can be concluded that high COD removal was obtained (4998 mg/L COD removal by EC and 10,047 mg/L COD removal by EF).     

The Effect of Ozonation on the Removal of Organics by Coagulation – Flocculation

We present here some works which take place in the particular framework of the study of drinking water treatment of reservoir waters which contain high concentrations of organics, mainly humic substances. Previous studies on coagulation of fulvic acid solutions have proved that the optimal removal of organic matter was reached at acidic pH with 2 mg of ferricion per mg or organic carbon (summarized in this paper). The main question in this study is to know what is the impact of preozonation on the removal of organics by iron (III) coagulation.

The study of the behavior of organics, in terms of UV-absorbance and TOC measurements was made on three aquatic fulvic acids and on two raw waters. The experiments carried out with fulvic acids showed that preozonation (at 0.5 mg O₃/mg C) of fulvic acid appeared to have shifted the region of the optimal DOC removal towards the higher coagulant dose. Furthermore, increasing ozone doses led to a slight decreasing of coagulation efficiency at constant coagulant dose. With two raw waters, preozonation at low ozone doses (0.2 mg 0₃/mg C) was found to improve very slightly the elimination of organic matter, while high ozone doses (0.9 mg O₃/mg C) led to a disturbance of TOC elimination by iron coagulation.     

Successful Removal of Algae through the Control of Zeta Potential

Abstract

Algae can interfere with treatment processes at a water treatment works. Coagulation control is critical to reduce the impact of algae on downstream processes. This paper investigates the coagulation and flotation of four species of algae – Asterionella formosa, Melosira sp., Microcystis aeruginosa, and Chlorella vulgaris. The zeta potential at optimum removal was measured and it was observed that when the zeta potential was reduced to between ?8 mV and +2 mV, removal of algae and associated organic material was optimized, irrespective of the coagulant dose or pH. Process control using zeta potential is therefore a viable tool for algae removal.     

Impact of Polymer Flocculants on Treated Water Quality in Surface Water Treatment by Coagulation-Microfiltration

The effects of polymer flocculants on coagulation/flocculation-microfiltration of two surface waters were investigated in terms of turbidity, dissolved organic matter concentration and molecular characteristics. The results showed that all polymers studied improved the dissolved organic carbon removal by polyaluminum chloride coagulation, but only cationic polymers improved UV ₂₅₄ removal. High performance size exclusion chromatography analyses showed that cationic polymers slightly increased removal of small UV absorbing matters in the molecular weight range of 1100 to 4000 Da compared to 4000–9000 Da by polyaluminum chloride only. These impacts have significant implications in the membrane fouling potential and permeate water quality of the pretreated water.     

Removal of Humic Acid Using PEI‐Modified Fungal Biomass

Abstract

A modified fungal biomass was prepared through the adsorption of polyethylenimine (PEI) and subsequent crosslinking with glutaraldehyde on the biomass surface. FTIR result verified that the amine groups were introduced on the biomass surface. As a large number of amine groups are present on the biomass surface and can be protonated in solution, the modified biomass was positively charged at pH<10.3. The modified biomass was used as an adsorbent to remove humic acid in a series of batch adsorption experiments. The amount of humic acid adsorbed on the biosorbent decreased with increasing solution pH, and the electrostatic interaction between the positive protonated amine groups on the biomass surface and the negative carboxyl groups in the humic acid molecules played an important role in humic acid adsorption. The time‐dependent sorption of humic acid on the biomass can be described well by the Fickian diffusion model at the initial stage and the pseudo‐second‐order equation over 10 h. Using the Langmuir adsorption isotherm, the maximum sorption capacity of the modified biomass for humic acid at pH 5 was 96.5 mg/g. The desorption experiments showed that the humic acid loaded biomass could be easily regenerated in a 0.1 M NaOH solution, and the regenerated biomass possessed good adsorption capacity up to the fifth cycle. The PEI‐modified biomass with polyamine chains shows the potential for application in water treatment for the removal of humic substances.     

Enhanced Coagulation/Flocculation by Combining Diatomite with Synthetic Polymers for Oily Wastewater Treatment

The objectives are to evaluate the feasibility of treating oily wastewater using synthetic polymers (polyaluminum chloride (PAC), polyferric sulfate (PFS), and polyacrylamide (PAM)) combined with natural diatomite and to refine the operating parameters using diatomite as an adsorbent and a coagulant aid. The enhanced coagulation/flocculation by combining PAC with diatomite was investigated through mechanism analysis compared to the combination of PFS/PAM with diatomite, respectively. The effects of coagulant dose, initial pH, and settling time on chemical oxygen demand (COD) and turbidity were studied using PAC-diatomite in comparison with using PAC only. The enhanced coagulation/flocculation of diatomite with PAC was better than that with PFS/PAM in terms of COD/turbidity removal and floc settling characteristics, considering costs. The PAC-diatomite system reduced more than 70% of COD and 90% of turbidity over a wide pH range (7–10) within 20 min, with the optimum dose of PAC 50 mg/l and diatomite 1250 mg/l. The added diatomite effectively saved over 85% of PAC dose and simultaneously increased over 50% of COD removal efficiency. This study provided a novel and economical approach for diatomite utilization in the treatment of oily wastewater, satisfying the demands of reuse or reinjection into the ground.     

Conditioning and Dewatering of Phosphorus-Rich Biological Sludge

The conditioning and dewatering of phosphorus-rich biological sludge, obtained from a pilot-scale biological phosphorus removal plant, was investigated. Dual conditioning utilizing a polyampholyte (AC4601) in combination with aluminum chloride (AlCl₃), ferric chloride (FeCl₃), and calcium chloride (CaCl₂) was studied. Capillary suction time (CST) and specific resistance to filtration (SRF) were utilized to assess sludge dewaterability. The dewaterability and removal of dissolved phosphorus from the phosphorus-rich sludge were examined. Compared with conditioning with only AC 4601, dual conditioning by adding 49 kg/ton of AlCl₃ prior to addition of AC4601 resulted in formation of large flocs, better dewaterability, and removal of 50% of soluble phosphorus. Better dewaterability, even larger flocs (> 1 cm), and 75% removal of soluble phosphorus were found when dosage of AlCl₃ increased to 189.2 kg/ton. The use of alumina (Al₂O₃) in combination with AC4601 could achieve equivalent dewaterability. However, only insignificant removal of soluble phosphorus (ca. 10%) was found. Sludge conditioning utilizing FeCl₃ and AC4601 was also very effective. A higher dosage of AC4601 was required and insignificant removal of soluble phosphorus was found when CaCl₂ was used in combination with AC4601. The interactions between hydrolyzed species of trivalent metal ions and polyampholyte contributed to enhanced dewaterability. Precipitates acted as skeleton builder and assisted in dewaterability as well. In addition, the removal of phosphorus was due to its precipitation reactions with metal ions. This study demonstrated an alternative way to condition phosphorus-rich sludge that could control the release of phosphorus from sludge to aqueous phase under anaerobic environment and achieve enhanced dewaterability simultaneously.     

Enhancing Biodegradability of Textile Wastewater by Ozonation Processes: Optimization with Response Surface Methodology

ABSTRACT

In this study, an ozonation process was used to increase biodegradability of textile wastewater by considering chemical oxygen demand (COD) and color removal. Response surface methodology was applied in order to determine the significance of independent variables which are initial pH, reaction time and ozone dose. While a biological oxygen demand (BOD)/COD rate of 0.315 was obtained at optimum conditions, which are pH 9, 75 min of reaction time and 26 mg/L ozone dose, color and COD removal was obtained at 74% and 39%, respectively. BOD/COD ratio value increased from 0.18 to 0.32 by ozonation process. In addition, k coefficient for BOD also increased from 0.21 to 0.30 d^?1.