DOC removal by multi-stage ozonation-biological treatment

Multi-stage ozonation-biological treatment process for dissolved organic carbon (DOC) removal was evaluated to apply for drinking water treatment. Waters with different types of DOC were used, i.e. a reservoir water for drinking water supply, a secondary effluent from a municipal wastewater treatment plant and a solution of humic substances extracted from leaf mold. The multi-stage ozonation-biological treatment process was compared with conventional single-stage ozonation-biological treatment process. Amount of DOC removed in biological treatment was defined as amount of biodegradable dissolved organic carbon (BDOC) in influent of biological treatment. DOC removal in the multi-stage ozonation-biological treatment was higher than that in the conventional single-stage ozonation-biological treatment with the same total ozonation time for the reservoir water and humic substances solution. Moreover, three- or four-stage ozonation for 5 min followed by biological treatment (total ozonation time 15 or 20 min) showed higher removal of DOC than the single-stage ozonation (60 min) and biological treatment. The higher DOC removal in the multi-stage treatment was due to the production of BDOC by ozonation. The long-term ozonation was not effective to produce BDOC because most of ozone was utilized to oxidize BDOC produced in the early stage of ozonation. In the multi-stage treatment, ozonation was effective to decompose refractory DOC and to produce BDOC because BDOC was removed by biological treatment. However, multi-stage ozonation-biological treatment was not effective for the secondary effluent. The reason seems to be high concentration of ozone scavengers in that water and low reactivity of DOC for ozone.     

Fractionation of dissolved organic matter from surface waters using macroporous resins

To obtain fractions enriched with biodegradable dissolved organic carbon (BDOC) or with organic compounds responsible for the chlorine demand (CID) and for trihalomethane formation potential (THMFP), Seine river water samples were percolated on various macroporous resins (anionic, cationic and non-ionic) and compared with granulated activated carbon (GAC). In addition, measurement of UV absorbance at 254 nm and the fluorescence index (λ_excitation 320 nm) had allowed to follow up the retention of dissolved organic matter by the different adsorbants. In contrast to cationic and non-ionic resins, anionic resins confirm their excellent retention capacity of organic compounds responsible for UV 254 absorbance and fluorescence index. The relative values of BDOC/DOC ratio (mg-C/mg-C) are slightly increased in the effluents of anionic resins, indicating that they retain a little preferentially the refractory fraction instead of the biodegradable fraction. There is no significant difference between the ratio of CID/DOC (mg-Cl₂/mg-C) in influent and effluent of anionic resins. Cationic resin has a low capacity for retention of DOC, but they seem to retain significantly the organic compounds responsible for CID. The capability of anionic resins to retain THMFP is similar to that of GAC.     

Indigenous bacterial inocula for measuring the biodegradable dissolved organic carbon (BDOC) in waters

A collaborative study was carried out in order to compare the biodegradable dissolved organic carbon (BDOC) analysis using different indigenous mixed bacterial populations as inocula. The variables examined in the study were the laboratories, the water samples (raw, ozonated or finished water), the origin of the inoculum: suspended bacteria from river waters and attached bacteria onto sand taken from drinking water treatment plants. Variances associated with individual components of this study were isolated: the laboratories represented the highest source of variation (56.6–70.7%), while the inoculum origin contribution to the increase of variance is lower (12–26%). As a conclusion, indigenous mixed bacterial populations (suspended or attached bacteria) may be used reliably as standard inocula in BDOC determinations without introducing excessive variability.     

Use of biodegradable dissolved organic carbon (BDOC) to assess the potential for transformation of wastewater-derived contaminants in surface waters

Wastewater-derived contaminants (WWDCs), such as steroid hormones, pharmaceuticals and personal care products, have been detected in surface waters at concentrations that pose potential risks to aquatic ecosystems. To assess the factors controlling biotransformation of these compounds in effluent-dominated surface waters (i.e., surface waters containing a high proportion of wastewater effluent), microcosm experiments were conducted with 10 pharmaceuticals and five steroids typically detected in wastewater effluent. Some of the compounds underwent rapid biotransformation under all conditions (estrone, 17beta-estradiol, progesterone, testosterone and triclosan), while carbamazepine was always resistant to biotransformation. For the remaining compounds, the rate of biotransformation was related to the amount and type of biodegradable dissolved organic carbon (BDOC). The rates of biotransformation of these WWDCs increased as the initial concentration of wastewater BDOC increased, indicating a relationship between microbial activity and biotransformation rate. Furthermore, BDOC derived from aquatic plants resulted in a better ability to remove certain recalcitrant compounds (gemfibrozil and sulfamethoxazole) as compared to that derived from wastewater effluent. These observations indicate that for each source of BDOC, it may be possible to use BDOC for predicting the rate of biotransformation of WWDCs in surface waters.     

混凝-微滤工艺提高饮用水生物稳定性的试验研究

以滦河水为处理对象,考察了混凝-微滤工艺对原水中营养物的去除效果和对饮用水生物稳定性的影响.该工艺对DOC的去除率随混凝剂投加量的提高而增加,在FeCl3投加量为2mg/L时,DOC的平均去除率达到22.4%.该工艺可有效去除可生物降解溶解性有机碳(BDOC)和总磷,并分别达到饮用水生物稳定性的阈值要求(BDOC<0.25mg/L和TP<5μg/L);同时,工艺出水的细菌再生长潜力(BRP)比原水降低1个数量级.因此采用混凝-微滤工艺可有效提高饮用水的生物稳定性,控制水中细菌再生长趋势.     

生物稳定性及生物稳定水制备工艺研究

生物稳定性是评价饮用水水质的重要指标。饮用水常规处理工艺不能有效去除AOC和BDOC,加氯消毒甚至会使AOC值升高,以太湖、黄浦江和长江为水源的常规处理工艺水厂的出厂水均不能满足生物稳定性的要求。曝气生物滤池和臭氧生物活性炭处理单元可以有效去除AOC和BDOC,曝气生物滤池+混凝气浮+臭氧生物活性炭+砂滤组合工艺出水经过消毒后能够满足生物稳定性的要求。     

纳滤膜出水的生物稳定性研究

利用纳滤膜(NF)对微污染的H市自来水进行深度处理试验与研究,用经氯化的含TOC为0.23～0.34mg/L纳滤水对模拟小型试验配水系统内异养型微生物的生长与繁殖情况进行检测和电镜观察,来探讨纳滤出水是否具有生物稳定性.结果表明:在已形成生物膜的不同材质的铸铁管和ABS管中通入5个半月纳滤水后,在系统的终端细菌总数由1.43×104cfu/mL缓慢减到2.1×103cfu/mL,并且ABS管上在5个半月的时间内未形成生物膜,但纳滤膜出水的AOC值还有待于进一步测定.     

Water Oxidation By Ozone Or Ozone/Hydrogen Peroxide Using The “Ozotest” Or “Peroxotest” Methods

This article presents a simple, rapid and efficient laboratory method permittingone to simulate the effects of ozonation (OZOTEST method) or of an oxidation by combined ozone/hydrogen peroxide (PEROXOTEST method) on an industrialscale. A critical analysis of the method is made (ozone transfer, validity of the results) and several practical applications are submitted for consideration (ozone demand, oxidation of atrazine and the DOC).     

饮用水水质生物稳定性研究进展

该文分析讨论了饮用水水质生物稳定性评价指标,包括AOC、BDOC、MAP、BGP和AOC—TDWMS等。论述了不同水处理工艺对生物稳定性的影响,得出常规处理对AOC和BDOC具有有限的去除能力;预处理工艺、强化常规处理工艺及深度处理工艺可有效地提高饮用水水质生物稳定性。同时,描述了管网中饮用水水质生物稳定性的特性变化,得出管网水中水质生物稳定性呈现规律性的变化;AOC和BDOC浓度沿管网延伸逐渐降低,或先升高后降低,这主要由水中余氯含量和微生物活性的占优势的一方决定。     

Membrane bioreactor process for removing biodegradable organic matter from water

This research investigated a membrane bioreactor (MBR) process for removing biodegradable organic matter (BOM) and trihalomethane (THM) precursors from pre-ozonated water. Bench-scale and mini-pilot-scale MBR experiments were conducted using powdered activated carbon (PAC) and acclimated biomass. Dissolved organic carbon (DOC) was removed through a combination of adsorption and biodegradation mechanisms, and the initial DOC removals depended on carbon dose, while steady-state removals were in the 20-60 percent range under various operating conditions. Both assimilable organic carbon (AOC) and total aldehydes were mostly removed to near detection limits and were not affected by PAC dosage. The AOC(NOX) removals were significantly higher than AOC(P17) or total AOC removals probably because the MBR microbial consortium was closer in characteristics to Aquaspirillum NOX than to Pseudomonas fluorescens (P17). The DOC was used instead of biodegradable organic carbon (BDOC) as a parameter for evaluating disinfection byproduct formation and bacterial regrowth potentials because BDOC assays did not yield consistent and conclusive results due to analytical difficulties. The removals of THM precursors were high when PAC was added; however, steady-state removals were a function of operating conditions and PAC dosage. Addition of PAC enhanced DOC removals and membrane permeate fluxes. Furthermore, pre-ozonation reduced membrane fouling and enhanced membrane permeate flux.