Ozone-biological activated carbon as a pretreatment process for reverse osmosis brine treatment and recovery

Ozonation was used in this study to improve biodegradability of RO brine from water reclamation facilities. An ozone dosage ranging from 3 to 10 mg O₃/L and contact times of 10 and 20 min in batch studies were found to increase the biodegradability (BOD₅/TOC ratio) of the RO brine by 1.8-3.5 times. At the same time, total organic carbon (TOC) removal was in the range of 5.3-24.5%. The lab-scale ozone-biological activated carbon (BAC) at an ozone dosage of 6.0 mg O₃/L with 20-min contact time was able to achieve 3 times higher TOC removal compared to using BAC alone. Further processing with Capacitive Deionization (CDI) process was able to generate a product water with better water quality than the RO feed water, i.e., with more than 80% ions removal and a lower TOC concentration. The ozone-BAC pretreatment has the potential of reducing fouling in the CDI process.     

Mineralization of some natural refractory organic compounds by biodegradation and ozonation

The objective of this study was to explore the extent of mineralization, reduction in color and reduction of COD of gallic acid, tannin and lignin by ozonation and a combination of aerobic biodegradation and ozonation. Ozonation of pure aliquots (phase I experiments) resulted in the decline in TOC, COD, COD/TOC ratio, UV absorbance at 280 nm and color of the three model compounds investigated, with COD removals of greater than 80% and high removals (>90%) of UV absorbance at 280 nm and color observed in all cases at an ozone dose of 6 mg ozone/mg initial TOC or higher. Aerobic biodegradation of pure gallic acid, tannin and lignin aliquots resulted in COD decline of approximately 36-38%. Subsequent ozonation (phase II experiments) resulted in further decline in TOC, COD, COD/TOC ratio, and increase in UV absorbance at 280 nm and color removals. COD and TOC removals comparable to phase I experiments were obtained with 30-40% lower ozone absorption in phase II experiments. The biodegradation step was quite effective in removing specific UV absorbance at 280 nm, with up to 75% removal observed. Subsequent ozonation increased overall specific UV absorbance at 280 nm to greater than 90%.     

压缩活性炭与超滤深度处理饮用水

研究了压缩活性炭净化饮用水的性能，并与超滤法去除有机污染的效果进行了比较，探讨了压缩活性炭—超滤工艺制备优质饮用水的可行性。试验结果表明，在流动状态下压缩活性炭去除有机污染的效率高于超滤，对CODMn、TOC、UV254和浊度的平均去除率分别为67．5％、74．1％、97．6％和50％以上，可用作超滤的预处理；压缩活性炭一超滤工艺可用于制备优质饮用水。     

The effect of polysaccharidic gums on activated carbon treatment of textile wastewater

The activated carbon treatment of wastewater originating from the Celanese Canada Ltd., Carpet plant at Sorel, Quebec, was tested in this study. Typical plant effluent was characterized and prepared. Soluble organics in the synthetic effluent varied between 75–185 mg TOC 1⁻¹, consisting of dyes (10%) process chemicals (75%) and the soluble guar gum (15%) used as a viscosity adjusting additive in the newly installed continuous dyeing process.The activated carbon adsorption of the guar gum from its pure solution was examined in laboratory tests. Improved adsorption was observed at low pH values and at elevated adsorption temperatures. Lignite-based carbon out-performed bituminous coal-based carbon. At 30 mg TOC 1⁻¹ of soluble guar gum, low carbon loading in the range of 3–8 mg TOC g^–1 was recorded for various types of carbon at 20°C and neutral pH.Activated carbon adsorption of the typical conventional prepared dyehouse wastewater resulted in non-adsorbable residues in the range of 9–18 mg TOC 1⁻¹. Presence of 50–100 mg of polysaccharidic guar gum per liter of conventional wastewater mixture had a pronounced positive effect on the adsorption process. This is reflected in an increase in both the carbon loading at initial concentration and the adsorption isotherm slope.     

Ozone-induced biodegradability of a non-ionic surfactant

An adaptation of the OECD biodegradability screening test was used to evaluate the ozone-induced biodegradability of a non-ionic surfactant, branched chain nonyl phenol ethoxylate. The higher the ozone dose the better the removal of non-ionic surfactants. Overall removal of 70% of COD and 62.5% of the TOC were achieved by biodegradation after ozonation, in comparison with 8–25% removal of COD and 23% of TOC during biodegradability test of the non-ozonized non-ionic surfactant. The improvement in biodegradability caused by ozonation can be explained as due to removing inhibitory effects by changes in the molecular structure, which further enhanced biodegradability.     

Removal of arsenic from water: Effects of competing anions on As(III) removal in KMnO4–Fe(II) process

Effects of sulfate, phosphate, silicate and humic acid (HA) on the removal of As(III) in the KMnO₄–Fe(II) process were investigated in the pH range of 4–9 with permanganate and ferrous sulfate applied at selected dosage. Sulfate decreased the removal of arsenic by 6.5–36.0% at pH 6–9 and the decrease in adsorption did not increase with increasing concentration of sulfate from 50 to 100 mg/L. In the presence of 1 mg/L phosphate, arsenic removal decreased gradually as pH increased from 4 to 6, and a sharp drop occurred at pH 7–9. The presence of 10 mg/L silicate had negligible effect on arsenic removal at pH 4–5 whereas decreased the arsenic removal at pH 6–9 and the decrease was more significant at higher pH. The presence of HA dramatically decreased the arsenic removal over the pH range of 6–9 and HA of higher concentration resulted in greater drop in arsenic removal. The effects of the competing anions on arsenic removal in the KMnO₄–Fe(II) process were highly dependent on pH and the degree of these four anions influencing As(III) removal decreased in the following order, phosphate > humic acid > silicate > sulfate. Sulfate differed from the other three anions because sulfate decreased the removal of arsenic mainly by competitive adsorption while phosphate, silicate and HA decreased the removal of As(III) by competitive adsorption and sequestering the formation of ferric hydroxide derived from Fe(II).     

The biodegradability of para-dichlorobenzene and its behaviour in model activated sludge plants

Confirmation of the ready and ultimate biodegradation of para-dichlorobenzine (pDCB) was obtained from the Organisation for Economic Cooperation and Development (OECD) closed bottle test. The fate of pDCB during primary sedimentation of raw sewage was investigated in a simple laboratory study, and the results indicated that the major proportion of the material (> 67%) remained in the supernant liquor, and would therefore undergo biological treatment. The removal of pDCB in the OECD confirmatory test was found to be consistently high (97.1 ± 2.3%). Mass balance results indicated that, at a high aeration rate (21 min⁻¹), the major mechanism for removal of pDCB was volatilization (66.6 ± 19.3%). The fate of pDCB in a modified porous pot test, operated at a lower aeration rate, and at temperatures of 8, 15, and 20°C and sludge retention times (SRT) of 3 and 6 days, was also investigated. Once again the overall removal was found to be consistently >95%. Mass balance results suggested that, under normal operating conditions, the major proportion of pDCB (>76%) had been removed by biodegradation. The amount of pDCB removed by volatilization showed a slight dependence on aeration rate, but only became significant (63 ± 4%) when adverse operating conditions prevailed (i.e. 8°C, at a 3 day SRT). Radioisotopic studies confirmed the presence of pDCB degrading bacteria in activated sludge taken from a porous pot continuously dosed with pDCB. The results of a similar test using sludge from an undosed porous pot suggested that acclimatization to pDCB was rapid, occurring within 2 days. No adverse effects on sewage treatment processes, due to the presence of pDCB, were observed.     

內压式超滤膜组合工艺处理北江水中试研究

以聚合氯化铝作为混凝剂,采用內压式超滤膜组合工艺处理北江水.结果表明,混凝沉淀-投加ClO2-超滤组合工艺出水浊度平均值为0.062 NTU;超滤能有效截留水中有机物和微生物,出水TOC保持在1.0 mg/L以下,菌落总数和大肠菌群均未检出;但超滤不能截留亚氯酸盐和氯酸盐.与常规工艺相比,内压式超滤膜组合工艺显著缩短了...     

Autopsy of high-pressure membranes to compare effectiveness of MF and UF pretreatment in water reclamation

A pilot-plant study was designed to compare the effectiveness of microfiltration (MF) and ultrafiltration (UF) as pretreatment for high-pressure membranes in reclamation of biologically treated wastewater effluent. Granular media, filtered secondary effluent from a full-scale wastewater treatment plant, was fed to MF and UF units that operated in parallel. Each of these filtrates served as the feedwater to two reverse osmosis (RO) units and one nanofiltration (NF) unit that operated in parallel. The decline in specific flux was substantially lower for high-pressure membranes receiving UF than MF pretreatment over the course of each of four pilot plant runs that lasted from 1 to 7 weeks. The removal of organic matter as measured by dissolved organic carbon (DOC) was somewhat higher by UF than MF pretreatment (about 15% by UF compared with 11% by MF). Addition of ferric chloride ahead of the UF unit, but not ahead of the MF unit, may account for this additional removal of organic matter. However, the additional DOC removal appeared insufficient to explain the differential in foulant accumulation between high-pressure membranes receiving UF and MF pretreatment. Extensive autopsy analyses of these high-pressure membranes showed from 35% to 56% less organic carbon on those receiving UF rather than MF pretreatment. A more specific indicator of a differential in organic fouling was the accumulation of polysaccharides and this showed from 27% to 38% less on UF- than on MF-pretreated membranes. Yet another possible source of foulants is inorganic material given that the inorganic and organic weight percentages were nearly equal (56% vs. 44%) on the membrane surface. One specific source was aluminum added for phosphorus removal. Less fouling of high-pressure membranes pretreated by UF than MF could be due to the following: (1) a small, but very important, colloidal fouling fraction may have passed through MF but was rejected by UF pretreatment; (2) organic fouling was not related to organics in either the MF or UF filtrates but rather to organics that are generated in situ by microbial activity on the membrane surface; and/or (3) less passage of colloidal Al-P that carried over from secondary wastewater treatment.     

Impact of support media in an integrated biofilter-submerged membrane system

The impact of a support material on an integrated biofilter-membrane system, simulating a difficult-to-treat surface water, was examined in terms of membrane fouling rate and water quality parameters. The support media in the membrane tanks did not generally affect any of the water quality parameters measured; however, there was an observable difference in the membrane fouling rates between the two processes with the support media system fouling at least two times slower than the non-support system. Total organic carbon (TOC) removals at around 60% were observed for two integrated biofilter-immersed membrane processes with the majority of the TOC removal occurring in the biofilters. One of the membrane tanks contained a support media (Process A) while the other did not (Process B). The feedwater contained humic acid (65% w/w) and readily biodegradable carbons (35% w/w) in the forms of acetic acid, formic acid and formaldehyde. The influent TOC values were between 3.35 and 3.94 mg/L. Acetate removals varied between 66 and 83%, while over 90% of the formate was removed and the formaldehyde was completely removed in the biofilters. There was a decrease in the UV absorbance values by over 70% for both processes.     

Feasibility of Treatment of Refinery Wastewater by a Pilot Scale MF/UF and UF/RO System for Reuse at Boilers and Cooling Towers

A pilot-scale hybrid membrane system, consisting of a ceramic microfilter (MF), two differentpolyvinyl chloride (PVC) and polyacrylonitrile (PAN) ultrafilters (UF), and a polyamide reverse osmosis (RO) filter, has been utilized to decrease harmful and damaging components in wastewater produced from Tehran Refinery with aim to be reused at boilers and cooling towers. Taguchi method was employed to find optimum operating conditions including transmembrane pressure, cross flow velocity (CFV), temperature, and backwash time. Further, analysis of variance (ANOVA) was performed to determine the significance of controlling factors on total organic carbon rejection and normalized permeate flux. MF (ceramic)/UF (PVC) system reduced, %: oil 99.7; chemical oxygen demand (COD) 82; biochemical oxygen demand (BOD) 79.3; conductivity 60.5; total dissolved solids (TDS) 52.6; turbidity 99.7 and total hardness 73.2. MF(ceramic)/UF (PAN) system reduced: oil, COD, BOD, conductivity, TDS, turbidity, and total hardness by 99.8; 84.2; 80.8; 62.72; 55; 99.9 and 78.4%, respectively. UF (PAN)/RO system decreased, %: oil 99.5; COD 99; BOD 99; conductivity 98; TDS 98; turbidity 98.7 and total hardness 99.94. Obtained treated wastewater by this system can be reused as feed water of boilers.     

Treatment using reverse osmosis of an effluent from stainless steel manufacture

Reverse osmosis (RO) and physical/chemical technology were evaluated for treatment of neutralized spent acid effluent (seepage) containing high concentration levels of TDS (7500 mg/l), Ca (400 mg/l), Cr^VI (42 mg/l), nitrate-nitrogen (827 mg/l), ammonia-nitrogen (33 mg/l), fluoride (13 mg/l), phenolics (45 mg/l) and COD (620 mg/l). The calcium concentration level in the seepage could be reduced from approximately 400 to 5 mg/l with soda ash softening. Initial permeate flux (feed and bleed system, 85% water recovery) was 278 l/m²·d. Permeate flux, however, dropped rapidly in the beginning of the run and then remained approximately constant to the end of the run. However, chemical cleaning of the membranes was necessary to maintain flux. The TDS of the RO feed could be reduced in one case from 34,253 to 1560 mg/l (95.5% removal) at 85% water recovery. Nitrate and ammonia nitrogen were reduced from 2691 and 103 mg/l to 414 (84.6% removal) and 15 mg/l (85.3% removal), respectively. Chromium^VI and fluoride were reduced from 183 and 90 mg/l to 0.38 (99.8% removal) and 2.8 mg/l (96.9% removal), respectively. COD removals varied between 60 and 80%. No phenolics, however, could be removed from the feed (approximately 32 mg/l) with the cellulose acetate RO membranes. Phenolics, however, could be effectively removed (<0.2 mg/l) from the RO permeate with hydrogen peroxide oxidation or ion-exchange treatment. Preliminary test work has shown that it should be possible to treat the seepage effectively with RO for pollution control, effluent volume reduction and water recovery. Capital costs for a 600 kl/d plant for lime softening, RO and oxidation equipment are estimated at U.S. $58,000, U.S. $350,000 and U.S. $87,500, respectively.     

混凝/PAC/超滤工艺去除水中天然有机物的研究

在饮用水处理过程中如何去除天然有机物是一个亟待解决的问题。混凝能降低水中污染物的浓度,避免这些物质进入膜孔内部,改善沉积在膜表面滤饼层的过滤性能和水中颗粒、胶体的迁移性能,提高膜通量。投加粉末活性炭(PAC)吸附溶解性有机物,利用超滤(UF)膜截留粉末炭,可达到提高出水水质的目的,还能防止膜污染。试验结果表明,混凝/PAC/UF组合工艺对水中UV254、UV410、TOC有较好的去除效果,平均去除率分别为92%、95%、84%,同时能改善膜透水通量、降低膜的吸附阻力、延长过滤周期、有效减少膜污染。     

Evaluation of wastewater reclamation technologies based on in vitro and in vivo bioassays

When municipal secondary effluent is used as the main supplementation water source for surface water bodies, its potential adverse ecological effects should not be neglected. The objective of this work was to investigate the effectiveness of several technologies, i.e. combination of coagulation and sand filtration (CSF), ultraviolet (UV) irradiation, chlorination, ozonation, ultrafiltration (UF) and reverse osmosis filtration (RO), on the removal of acute ecotoxicity, genotoxicity and retinoic acid receptor (RAR) agonist activity from the municipal secondary effluent. The effects of treated effluents on the development of Japanese medaka (Oryzias latipes) embryos were also evaluated. The secondary effluent exhibited a mutagenic effect on Salmonella typhimurium strain TA 1535/pSK1002, acute invertebrate toxicity to Daphnia magna, and weak RAR α activity. RO and ozonation demonstrated remarkable removals of the genotoxic effect, acute toxicity and RAR activity from secondary effluent, while chlorination could elevate both genotoxicity and acute toxicity. CSF, UV, UF, chlorination as well as RO could decrease the 4-day mortality of medaka embryos and accordingly increase the hatching success rate, comparing with the secondary effluent. Ozonation at 4 mg/l and higher doses, however, elicited significantly higher 4-day mortality, leading to the reduction of the hatching success rate.     

Experimental study of the supercritical water oxidation of recalcitrant compounds under hydrothermal flames using tubular reactors

The hydrothermal flame is a new method of combustion that takes place in supercritical water oxidation reactions when the temperature is higher than the autoignition temperature. In these conditions, waste can be completely mineralized in residence times of milliseconds without the formation of by-products typical of conventional combustion. The object of this work is to study the hydrothermal flame formation in aqueous streams with high concentrations of recalcitrant compounds: an industrial waste with a high concentration of acetic acid and various concentrated solutions of ammonia. A tubular reactor with a residence time of 0.7 s was used. Oxygen was used as the oxidant and isopropyl alcohol (IPA) as co-fuel to reach the operation temperature required. The increase of IPA concentrations in the feeds resulted in a better TOC removal. For mixtures containing acetic acid, 99% elimination of TOC was achieved at temperatures higher than 750 °C. In the case of mixtures containing ammonia, TOC removals reached 99% while maximum total nitrogen removals were never higher than 94%, even for reaction temperatures higher than 710 °C. Ignition was observed at concentrations as high as 6% wt NH₃ with 2% wt IPA while at IPA concentrations below 2% wt IPA, the ammonia did not ignite.     

Enhanced uptake of phosphorus by activated sludge-effect of substrate addition

Studies were undertaken to examine the effect of substrate addition upon the release and subsequent uptake of phosphorous by a biological wastewater treatment laboratory scale system.A train of six reactors were fed at a rate of 16 ml min⁻¹ raw wastewater using a sludge recycle ratio of 0.75 (12 ml min⁻¹). The first two reactors were simply stirred (anoxic) without the addition of air and the remaining four were aerated with excess air.Various substrates were added to the first reactor (anoxic) at different concentrations. It was determined that all the short chain substrates tested enhanced the release of phosphorus in the anoxic stages and subsequently led to increased biological uptake (removal) of phosphorus. The substrates tested included sodium acetate, acetic acid, butyric acid, ethanol and methanol.It was determined that 30 mg l⁻¹ sodium acetate was the optimum dose for biological release and uptake of phosphorus and the addition of any greater concentration had marginal effect on the ultimate removal of phosphorus.The effect of these substrates showed some specificity regarding phosphorus release, with butyric acid causing the greatest release and sodium acetate the least. However as far as phosphorus uptake (removal) was concerned, this phenomenon of substrate-specificity was less significant. For all substrates, effluent phosphorus concentration was within ± 1 mg l⁻¹ with an approximate mean concentration of 1 mg l⁻¹ residual.Phosphorus released (approx. 14 mg l⁻¹) at higher temperature (29°C) was 75% greater than at the lower temperature (24°C). Similarly the final residual phosphorus at 29°C was 33% lower than at 24°C.     

超滤膜/混凝生物反应器去除饮用水中有机物的效能

采用超滤膜/混凝生物反应器(UF-MCBR)处理模拟微污染源水,考察了对有机污染物的去除效能与机理.结果表明,当聚合氯化铝投加量为10mg/L时,UF-MCBR对DOC、UV254、TOC、CODMn、BDOC和AOC的去除率分别为44.0%、54.5%、49.0%、58.5%、72.8%和58.3%.UF-MCBR通过超滤、生物降解以及混凝三者之间的协同作用去除溶解性有机物,就DOC的去除而言,三种作用的贡献率分别为11.1%、6.2%和26.7%.UF-MCBR系统中的UF膜表面为污泥层所覆盖,该污泥层能有效强化UF膜对分子质量为300-6000u 有机物的截留,UF膜(连同污泥层)对僧水碱、憎水中性物、憎水酸、弱憎水酸和亲水性物质的截留率分别达到了37.0%、42.8%、52.7%、39.8%和19.0%.     

Adsorption combined with ultrafiltration to remove organic matter from seawater

Organic fouling and biofouling are the major severe types of fouling of reverse osmosis (RO) membranes in seawater (SW) desalination. Low pressure membrane filtration such as ultrafiltration (UF) has been developed as a pre-treatment before reverse osmosis. However, UF alone may not be an effective enough pre-treatment because of the existence of low-molecular weight dissolved organic matter in seawater. Therefore, the objective of the present work is to study a hybrid process, powdered activated carbon (PAC) adsorption/UF, with real seawater and to evaluate its performance in terms of organic matter removal and membrane fouling. The effect of different PAC types and concentrations is evaluated. Stream-activated wood-based PAC addition increased marine organic matter removal by up to 70% in some conditions. Moreover, coupling PAC adsorption with UF decreased UF membrane fouling and the fouling occurring during short-term UF was totally reversible. It can be concluded that the hybrid PAC adsorption/UF process performed in crossflow filtration mode is a relevant pre-treatment process before RO desalination, allowing organic matter removal of 75% and showing no flux decline for short-term experiments.     

Removal of indigenous rotaviruses during primary settling and activated-sludge treatment of raw sewage

An eight month study of indigenous rotavirus removal during primary settling and activated sludge treatment of raw sewage was made in a plant in Houston, Texas treating 1.5 million gal day⁻¹. An average reduction of 44–55% was obtained by primary settling and a 93–99% reduction was achieved in final chlorinated effluents. Composite sampling at 1 h intervals over a 24 h period indicated average removals of 85% compared to a misleading 6% indicated by one set of grab samples of raw sewage and effluent collected simultaneously. Quantification of rotaviruses was made by immunofluorescent foci counts 24 h after addition of sample concentrates to coverslip cultures of fetal rhesus kidney cells. Rotaviruses varied from 40–5101⁻¹ of raw sewage and from 0 to 25 in the final chlorinated effluent.     

Preparation and evaluation of iron–chitosan composites for removal of As(III) and As(V) from arsenic contaminated real life groundwater

A study on the removal of arsenic from real life groundwater using iron–chitosan composites is presented. Removal of arsenic(III) and arsenic(V) was studied through adsorption at pH 7.0 under equilibrium and dynamic conditions. The equilibrium data were fitted to Langmuir adsorption models and the various model parameters were evaluated. The monolayer adsorption capacity from the Langmuir model for iron chitosan flakes (ICF) (22.47 ± 0.56 mg/g for As(V) and 16.15 ± 0.32 mg/g for As(III)) was found to be considerably higher than that obtained for iron chitosan granules (ICB) (2.24 ± 0.04 mg/g for As(V); 2.32 ± 0.05 mg/g for As(III)). Anions including sulfate, phosphate and silicate at the levels present in groundwater did not cause serious interference in the adsorption behavior of arsenate/arsenite. The column regeneration studies were carried out for two sorption–desorption cycles for both As(III) and As(V) using ICF and ICB as sorbents. One hundred and forty-seven bed volumes of As(III) and 112 bed volumes of As(V) spiked groundwater were treated in column experiments using ICB, reducing arsenic concentration from 500 to <10 μg/l. The eluent used for the regeneration of the spent sorbent was 0.1 M NaOH. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to <10 μg/l from real life arsenic contaminated groundwater samples.