Control of bromate ion and brominated organic compounds formation during ozone/hydrogen peroxide treatment of secondary effluent.

Ozonation and ozone process combined with hydrogen peroxide have been identified as new technologies for direct or indirect reuse of wastewater. This study aims to establish appropriate conditions to control the formation of BrO3 and brominated organic compounds during O3/H2O2 treatment of secondary effluents of sewage. When the H2O2/O3 mole ratio of injection was above 0.5 and the DO3 concentration was below 0.1 mg/L, BrO3 was controlled as well as treatment purpose was completed. TOBr formation in O3/H2O2 treatment was also completely controlled.     

Advanced oxidation process-biological system for wastewater containing a recalcitrant pollutant.

Two advanced oxidation processes (AOPs), ozonation and photo-Fenton, combined with a pilot aerobic biological reactor at field scale were employed for the treatment of industrial non-biodegradable saline wastewater (TOC around 200 mgL(-1)) containing a biorecalcitrant compound, alpha-methylphenylglycine (MPG), at a concentration of 500 mgL(-1). Ozonation experiments were performed in a 50-L reactor with constant inlet ozone of 21.9 g m(-3). Solar photo-Fenton tests were carried out in a 75-L pilot plant made up of four compound parabolic collector (CPC) units. The catalyst concentration employed in this system was 20 mgL(-1) of Fe2+ and the H2O2 concentration was kept in the range of 200-500mgL(-1). Complete degradation of MPG was attained after 1,020 min of ozone treatment, while only 195 min were required for photo-Fenton. Samples from different stages of both AOPs were taken for Zahn-Wellens biocompatibility tests. Biodegradability enhancement of the industrial saline wastewater was confirmed (>70% biodegradability). Biodegradable compounds generated during the preliminary oxidative processes were biologically mineralised in a 170-L aerobic immobilised biomass reactor (IBR). The global efficiency of both AOP/biological combined systems was 90% removal of an initial TOC of over 500 mgL(-1).     

Recalcitrant COD degradation by an integrated system of ozonation and membrane bioreactor.

In order to treat wastewater to a low residual COD-concentration such as 125 mg/L, classical biological treatment is not sufficient for many types of industry. This research focused on the integrated treatment of the wastewater of the paper industry, with a membrane bioreactor (MBR) and an oxidation step. The optimal configuration was examined. Screening tests with different types of oxidation showed that ozonation after biological treatment could reduce the COD with 40% with an ozone dose of 0.4-0.8g O3/g COD. BOD/COD ratio could be increased up to 0.19. Neither combination of ozone with UV and/or hydrogen peroxide nor the process H2O2/UV or (photo-)Fenton reagents gave any improvement in COD reduction or BOD increase, unless the doses were very high. Based on these results, an integrated system MBR-ozonation was designed, with recirculation of MBR effluent over ozonation. This test showed that reduction of COD up to 125 mg/L immediately behind the MBR required a lot of ozone. A technically feasible solution was to discharge the water after an extra ozonation step, which resulted in a high total ozone dosage. The alternative, the consecutive treatment activated sludge-ozonation-activated sludge, did not give a better COD-removal with the same ozone dose as the integrated concept. The economic evaluation proves that the integrated chemical and biological treatment is expensive for the paper industry if a low discharge limit of COD has to be complied with.     

Treatment of oilfield wastewater by Fenton's process.

A combination of coagulation and Fenton's process was used for the removal of total oxygen carbon (TOC) from oilfield wastewater. Compared with aluminium sulfate, ferric coagulant had better TOC removal efficiency at the same mass dosage. In Fenton's process, the effect of H2O2 and Fe2+ dose on the removal of TOC was studied. The optimum conditions required for TOC removal were an Fe3+ concentration of 40-50 mg/L, an H2O2 dose of 50 mmol/L and an Fe2+ concentration of 1.0 mmol/L. GC-MS chromatographic analysis indicated that most of the alkyl hydrocarbons of carbon numbers < 21 were removed in the first minute of Fenton's process mainly through adsorption. Alkyl hydrocarbons and phenols were oxidized almost completely following 120 min of treatment. The pathway of newly formed intermediates in Fenton's process was proposed on the basis of the GC/MS chromatogram.     

Fenton氧化处理甲基橙染料模拟废水的动力学研究

采用Fenton试剂降解含甲基橙染料的模拟废水,通过对甲基橙染料处理过程中UV-Vis吸收光谱的分析,证明了Fenton氧化法对甲基橙染料的处理效果。进一步研究了Fenton氧化降解甲基橙废水的反应动力学,并建立了反应动力学模型。结果表明,Fenton氧化过程中,影响甲基橙降解速率的主要因素为H2O2和甲基橙的初始浓度。H2O2和甲基橙初始浓度与反应速率常数之间的关系可分别归纳为:kRH=0.05c(H2O2)1.4和kRH=0.023c(RH)-1.3。     

Treatment of slaughterhouse plant wastewater by using a membrane bioreactor

The use of a membrane bioreactor (MBR) for removal of organic substances and nutrients from slaughterhouse plant wastewater was investigated. The chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations of slaughterhouse wastewater were found to be approximately 571 mg O2/L, 102.5 mg/L, and 16.25 mg PO4-P/L, respectively. A submerged type membrane was used in the bioreactor. The removal efficiencies for COD, total organic carbon (TOC), TP and TN were found to be 97, 96, 65, 44% respectively. The COD value of wastewater was decreased to 16 mg/L (COD discharge standard for slaughterhouse plant wastewaters is 160 mg/L). TOC was decreased to 9 mg/L (TOC discharge standard for slaughterhouse plant wastewaters is 20 mg/L). Ammonium, and nitrate nitrogen concentrations of treated effluent were 0.100 mg NH4-N/L, and 80.521 mg NO3-N/L, respectively. Slaughterhouse wastewater was successfully treated with the MBR process.     

Comparison of the efficacy of oxidative processes and flocculation for the removal of colour from Eop effluent.

Up to 30% of the released colour arising from bleached kraft pulp and paper production comes from the alkaline extraction stage. This waste stream can therefore be readily targeted to remove colour at source in mills where improved colour management is required. The efficacy of five advanced oxidative treatment and physico-chemical technologies in removing colour from a typical Eop stage effluent was compared. The most effective oxidative treatment was peroxymonosulphate (79% colour removal in 15 minutes). Ozone and TAML treatments removed 74% and 58% of colour respectively within 30 minutes. In comparison, hydrogen peroxide alone was only able to remove 35% of the colour over 4 hours. Coagulation with polyaluminium chloride achieved 89% colour removal within 5 minutes. However, this treatment produced an undesirable sludge, and may cause toxicity in the treated wastewater. Overall, colour removal ability of the five technologies ranked from highest to lowest was polyaluminium chloride > peroxymonosulfate > ozone > TAML > hydrogen peroxide. Other factors, such as operating costs, feedstock modification and capital infrastructure, also need to be taken into account when selecting the most suitable colour management option.     

The effects of dissolved organic matter on the decomposition of di-n-butyl phthalate by ozone/hydrogen peroxide process.

The effects of the dissolved organic matter (DOM) on the ozone decay and the di-n-butyl phthalate (DBP) decomposition during ozone/hydrogen peroxide (O3/H2O2) process were investigated (DBP-d4 was used instead of DBP). Four surface waters, two secondary municipal sewage effluents (SMSEfs) and Suwannee river natural organic matter were used as DOM. The ozone decompositions in the DOM solutions were separated by instantaneous ozone consumption and slower ozone decay. The effect of H2O2 addition on the ozone decay was clearly observed at slower ozone decay. Ozone decomposition rate at slower ozone decay increased linearly with H2O2 dose. DBP-d4 was exponentially decreased with ozone consumption. Ozone consumption required to decompose 90% of DBP-d4 ((deltaO3)90%) in SMSEFs was higher than those in surface waters. The (deltaO3)90% per DOC of DOM values were from 22 to 23 micromole/mgC for SMSEFs and from 10 to 17 micromole/mgC for surface waters. The (deltaO3)90% values were correlated to specific ultraviolet absorbance at 254 nm (SUVA254) for surface waters.     

H2O2/UV enhanced degradation of pesticides in wastewater.

Photodegradation of organic pesticides in industrial wastewater was examined in a UV/H2O2/air system. An experimentally determined optimal amount of hydrogen peroxide (0.008% v/v) indicates that hydrogen peroxide concentration controlled the efficiency of photodegradation. Pre-treatment operations such as sedimentation, filtration and coagulation were used to obtain better efficiency of pesticide removal and to cut down on irradiation time. Finally, scale-up experiments in the air-sparged hydrocyclone (ASH) reactor were carried out. After 5 min irradiation of 100 dm3 industrial wastewater almost all pesticides were destroyed. Thus the ASH reactor proved to be an effective contactor for carrying out photochemical reactions.     

Decolorization and mineralization of Oolong tea polyphenols in colored soft drink wastewater by photo Fenton reaction

The decolorization and the mineralization of the colored soft drink wastewater including Oolong tea polyphenols by the photo Fenton reaction have been investigated. The decolorization of the colored soft drink wastewater including Oolong tea polyphenols by the photo Fenton reaction could be divided into 3 phases. Just after H2O2 was added to the solution, the color of the solution immediately increased from absorbance of 0.247 to 0.711 at the wavelength of 400 nm, which was defined as the 1st phase. Subsequently the significant decolorization by the photo Fenton reaction occurred at the 2nd phase. Finally, complete decolorization (the color attributed to the color of Fe3+) could be achieved in 180 min at the 3rd phase. The instantaneous and considerable color increase at the 1st phase could be attributed to the formation of intermediate colored compounds like quinones and soluble iron complexes produced by the Fenton reaction. About 95% mineralization of model colored soft drink wastewater with 229 mg L(-1) initial TOC concentration was achieved after 165 min.     

Effect of ozone, chlorine and hydrogen peroxide on the elimination of colour in treated textile wastewater by MBR.

In treating textile wastewater, the application of membrane bioreactor (MBR) technology showed high efficiency in COD and BOD5 removal. However, insufficient colour removal was achieved for possible reuse. The aim of the work presented in this paper was to test the performance of chemical advanced oxidation on the elimination of the colour downstream of an MBR. To improve the quality of the membrane bioreactor effluent three different oxidation treatments were tested at lab-scale: ozonation, chlorination and hydrogen peroxide oxidation. Colour, COD and BOD5 were controlled in order to assess the effectiveness of each process. For chlorination, even with 250 mg/L (active chlorine) only 80% colour removal (SACin = 14; SACout = 2.8) was achieved which is considered unsatisfactory. For hydrogen peroxide, the colour removal was even poorer; it was just 10% at a concentration of 250 mg/L. In contrast, good results were obtained by ozonation. By using only 38 mg/L within 20 minutes, it was possible to achieve the reuse recommendation with a satisfactory colour removal of 93% (SACin = 14; SACout = 0.98). The results showed that ozonation was the most promising method.     

Combining photo-Fenton process with biological sequencing batch reactor for 2,4-dichlorophenol degradation.

The effect of the photo-Fenton process on biodegradability enhancement of 100 mg x L(-1) aqueous 2,4-dichlorophenol (2,4-DCP) solution has been investigated. An initial concentration of 65 mg x L(-1) H2O2 and 10 mg x L(-1) Fe (II) during 35 minutes of irradiation time was sufficient for total 2,4-DCP removal. At these working conditions, biodegradability, measured as BODS/COD ratio, was increased from 0 for the original solution up to 0.15. Biological oxidation of photo-Fenton pre-treated solutions was performed in a sequencing batch reactor (SBR). After 32 days of start-up, the reactor was fed with different pre-treated solutions and cycle duration was reduced progressively. TOC removal efficiencies in the SBR went from 30 up to 70%.     

Characteristics of estrogen decomposition by ozonation.

Since the natural estrogens 17 beta-estradiol (E2) and estron (E1), and the synthetic estrogen 17 alpha-ethynyl estradiol (EE2) have strong endocrine disrupting effects and the tendency to persist in effluent from wastewater treatment plants, effective measures are needed to remove them from wastewater. In this research, to gain an understanding of the characteristics of estrogen decomposition by ozonation, experiments were conducted using effluent from an actual wastewater treatment plant. In this experiment, estrogen was added to effluent at a concentration of 200 ng/l and 20 ng/l before the ozonation experiments. The results showed 90% or more of estrogen concentration and estrogenic activity of E2, El and EE2 to be removed at an ozone dose of 1 mg/l. At an ozone dose of 3 mg/l, the estrogen concentration and estrogenic activity of E2, El and EE2 in the treated water fell below the detection limit. The removal rate was not influenced by the kind of estrogen. No generation of byproducts with estrogenic activity was observed. The authors conclude that estrogen in secondary treated wastewater can be almost entirely removed at the practical ozone dose rate applied for the purpose of disinfection, which is up to about 5 mg/l.     

ANAMMOX工艺在生活污水深度处理中的应用研究

随着水环境质量的恶化,高能低耗的污水深度处理技术成为当前研究热点,尤其是对于低C/N比的城市生活污水脱氮技术的研究。试验以城市生活污水的二级出水为研究对象,采用ANAMMOX下向流生物滤池,当二级出水NH3-N=15-35mg/L,CODCr=25-45mg/L,TOC=9-12mg/L,水温=25-28℃时,ANAMMOX下向流生物滤池脱氨率达80%-100%,不仅适用于处理高氨废水,也可用于城市生活污水深度处理中。试验发现pH可以用来指示ANAMMOX反应的进行,同时也可以用来指示ANAMMOX反应进程的快慢。试验中还发现,厌氧氨氧化反应速率与NO2--N含量有关,原水中NO2--N含量的增多有利于ANAMMOX工艺处理效果。     

Photocatalytical polishing of paper-mill effluents.

Photocatalytic oxidation (PCO) is a promising technology for purification of biological pretreated wastewater or destruction of non-biodegradable compounds. For this reason PCO has been investigated as a last step of purification of biologically pre-treated paper-mill effluents. The influence of the parameters pH, TiO2-modification, TiO2-concentration, catalyst re-use, concentration of substances to be oxidised (wastewater quality) has been determined. The TOC of the biologically pretreated wasterwater was up to 55 mg L(-1). This wastewater was treated with a previously presented aerated cascade photoreactor which was modified for batch experiments. A high specific oxidation rate of up to 0.76 g TOC m(-2) h(-1) as well as a complete TOC mineralization has been achieved after the optimisation of the process parameters. The complete destruction of recalcitrant compounds will offer the opportunity to reuse the wastewater in the production process. The increase of the BOD5/TOC ratio after a short irradiation period indicates the transformation of recalcitrant organic compounds to better biodegradable intermediates. The use of PCO as a pre-treatment step for the enhancement of the biodegradability of wastewater, containing recalcitrant or inhibitory compounds is an alternative to a long and energy-intensive total pollutant mineralization.     

Evaluation of phytotoxic elements, trace elements and nutrients in a standardized crop plant, irrigated with raw wastewater treated by APT and ozone.

This project studied the benefits of applying Advanced Primary Treatment (APT) and ozone (O3) to raw wastewater destined for reuse in agriculture. The ozone was applied directly to raw wastewater, as well as to wastewater already treated with APT, and the results compared against a control sample of potable water. The experimental conditions that reported the best results was wastewater treated with O3 (at a dose of 4.8 mg/L, at pH 7, temperature 23 degrees C, for 1 hr), given that it met standards in force in Mexico with regard to micro-organism and heavy metal content. Under these conditions, after 15 min of ozonation, 100% destruction of the following bacteria was observed: V. cholerae, S. typhi as well as total and faecal coliforms. Destruction of helminth eggs and Giardia sp. took one hour. No phytotoxic elements or heavy metals were found. The balance of nutrients N:P:K (300:100:200 mg/kg) required for lettuce growth, was found in wastewater subjected to both treatment plans. However, ozone favoured the nitrification and assimilation of the nutrients, by contributing oxygen to the soil. Therefore, these conditions produced the greatest lettuce growth, the entire plant averaging 38 cm in length and 125 g. in weight. Moreover, a better appearance of the leaves was also noted.     

AOPs with ozone and UV radiation in drinking water: contaminants removal and effects on disinfection byproducts formation.

In this study, the advanced oxidation with ozone and UV radiation (with two low pressure UV lamps, at 254 and 185 nm wavelength) were experimented on a surface water in order to study the removal of two odorous compounds (geosmin and 2-methylisoborneol) and a pesticide (metolachlor), the influence on organic compounds (UV absorbance and THM precursors) and bromate formation. Different batch tests were performed with ozone concentration up to 10 mg/L, UV dose up to 14,000 J/m2 and a maximum contact time of 10 minutes. The main results show that metolachlor can be efficiently removed with ozone alone while for geosmin and MIB a complete removal can be obtained with the advanced oxidation of ozone (with concentration of 1.5-3 mg/L and contact time of 2-3 minutes) with UV radiation (with doses of 5,000-6,000 J/m2). As concerns the influence on the organic precursors, all the experimented processes show a medium removal of about 20-40% for UV absorbance and 15-30% for THMFP (trihalomethanes formation potential). As concerns bromate formation, the advanced oxidation of ozone/UV 254 nm shows a bromate formation that is about 40% lower with respect to conventional oxidation with ozone.     

A modified advanced Fenton process for industrial wastewater treatment.

For the first time hydrodynamic cavitation induced by a liquid whistle reactor (LWR) has been used in conjunction with the advanced Fenton process (AFP) for the treatment of industrial wastewater. Semi-batch experiments in the LWR were designed to investigate the performance of the process by optimising various parameters such as pressure, pH, H2O2 concentration and the concentration of industrial wastewater samples on the mineralisation of the total organic carbon (TOC). It was found that higher pressures are more favourable for a rapid TOC mineralisation.     

过氧化氢处理河流着生刚毛藻的效果研究

以深圳市某河流为研究对象,分析了投加H2O2对刚毛藻生物量的控制效果及其对水体p H、溶解氧、氨氮和总磷的影响。结果表明:H2O2≥1.25 mol/L时能有效抑制刚毛藻生长,使藻类光合活性在10 min内从5.8降低到0,叶绿素浓度在30 min内从5.8 mg/L降低至0.2 mg/L。现场试验投加H2O2处理河流水体中刚毛藻14 d内,藻类生物量、光合活性和叶绿素浓度降幅均高于90%。加药1 h后,河流p H值由原来的9.21~9.74迅速降低至8.23~8.80,14 d内保持在9以下。河流溶解氧、氨氮、总磷和H2O2残留浓度在除藻过程中存在变化,但是1 d后会迅速恢复至加药前水平。投加H2O2是一种有效、无污染的应急去除河流着生刚毛藻的方法。     

The basics of oxidants in water treatment. Part B: ozone reactions.

The oxidation of organic and inorganic compounds during ozonation can occur via ozone or OH radicals or a combination thereof. Ozone is an electrophile with a high selectivity. The reactions of ozone with inorganic compounds are typically fast and occur by an oxygen atom transfer reaction. Organic micropollutants are oxidised with ozone selectively. Ozone reacts mainly with double bonds, activated aromatic systems and non-protonated amines. The kinetics of direct ozone reactions depend strongly on the speciation (acid-base, metal complexation). The reaction of OH radicals with the majority of inorganic and organic compounds is nearly diffusion-controlled. The degree of oxidation by ozone and OH radicals is given by the corresponding kinetics and the ratio of the concentration of the two oxidants. Product formation from the ozonation of organic micropollutants has only been established for a few compounds. Numerous organic and inorganic ozonation disinfection/oxidation byproducts have been identified. The byproduct of main concern is bromate, which is formed in bromide-containing waters. A low drinking water standard of 10 microgL(-1) has been set for bromate. In certain cases (bromide > approximately 50 microgL(-1)), it may be necessary to use control measures to lower bromate formation (lowering of pH, ammonia addition, chlorination-ammonia process).