Disinfection of secondary effluents using tin oxide anodes.

Direct current applied to a tin oxide anode submersed in water has the potential to generate hydroxyl radicals, a strong chemical oxidant. Tin oxide anode systems, which may represent a viable alternative disinfectant, were investigated for the disinfection of secondary effluents. Coliform bacteria in the effluent were effectively inactivated in a bench-scale tin oxide disinfection system. The number of anodes in the tin oxide disinfection system influenced the steady-state concentration of hydroxyl radicals and, consequently, the contact time necessary to achieve a specified dose. The life expectancy of the anodes was greater than 30 days and no appreciable loss of tin was observed over a 5-day period. A preliminary estimate of the capital and operating costs of a pilot- or full-scale tin oxide disinfection system designed to meet a discharge requirement of 23 most probable number/100 mL at a 3 785-m3/d (1-mgd) facility was comparable to UV and chlorination/dechlorination facilities. Based on this preliminary assessment, tin oxide disinfection systems are a promising alternative disinfectant for secondary effluents.     

The effect of wastewater treatment on antibiotic resistance in Escherichia coli and Enterococcus sp.

The effects of wastewater treatment on the proportion of Escherichia coli and Enterococcus sp. resistant to specific antibiotics were investigated at two facilities in Davis County, Utah, one of which received hospital waste. Samples were taken from the influent, effluent before disinfection, and secondary anaerobic sludge digester effluent. There was very little difference in antibiotic resistance among E. coli in the inflow waters of the plants but the plant receiving hospital waste had a significantly higher proportion of antibiotic resistant Enterococcus. The effect of wastewater treatment on antibiotic resistance was more pronounced on enterococci than E. coli. Although some increases in antibiotic resistance were observed, the general trend seemed to be a decrease in resistance, especially in the proportion of multidrug resistant Enterococcus sp.     

不同来源高浓度有机废水的集中处理

按照水质情况,将多种来源于不同工业生产过程中的高浓度有机废水划分为高悬浮固体乳化液废水、难生化高浓度有机废水、高悬浮固体不含油有机废水、含铬有机废水和杂质含量较少的乳化液废水5类,分别采用酸化破乳/Fen-ton氧化/混凝/絮凝、Fenton氧化/混凝/絮凝、混凝/絮凝、还原/混凝/絮凝、震动膜过滤技术作为生化预处理技术,并通过小试和中试验证了各技术的效果。实验结果表明,按照上述分类结果,采用不同预处理技术可以得到良好的效果,废水水质明显改善,满足继续生化处理的基本条件。各预处理生产装置处理效果稳定,同时生化系统已经稳定运行120天以上,COD去除率超过90%,出水经过低剂量的Fenton试剂处理后可达到《污水排入城镇下水道水质标准》(CJ343-2012)。     

Aerobic Treatment of a Nitrogen-Limited Chemical Process Waste water

Abstract

Nitrogen transformations and their effect on aerobic suspended growth treatment of an industrial wastewater were studied in three parallel bench-scale reactors operated at 5 "C at mean cell residence times (MCRT) of 15, 30, and 60 days. In normal process wastewater, the bulk of influent nitrogen was in organic form, and the fraction transformed was almost totally incorporated into synthesized biomass. Assimilative control by heterotrophs maintained ammonianitrogen levels below permitted effluent levels, and nitrification was not significant. Although volatile suspended solids had a nitrogen content of only 5% to 8%, effective organics removal was maintained, and total organic carbon and filtered daily average five-day biochemical oxygen demand (BODS) were below permitted effluent levels. A marked improvement in settleability and lower effluent total suspended solids was achieved by adding ammonia-nitrogen to the wastewater in excess of stoichiometric growth requirements.

During a batch production cycle of a cationic chemical, the ratio of nitrogen to chemical oxygen demand and the fraction of the total influent nitrogen in soluble form increased in the wastewater. Reactor effluent ammonia levels increased to above permit levels at all three MCRTs during treatment of wastewater containing cationic production effluents. The magnitude of ammonia increase was greater for longer MCRTs, suggesting that synthesis of cell mass was not capable of assimilating the increased ammonia supply under these non-steady conditions. The experimental results suggest several potential strategies for operating the aerobic process at the treatment facility, including adding nitrogen to improve settleability and discontinuing these additions when wastewater contains a high ratio of nitrogen to chemical oxygen demand and an elevated soluble nitrogen fraction     

Air Pollution in the Republic of Korea

This paper discusses the potential for using commercially available treatment techniques to remove VOCs from hazardous waste streams and addresses some of the issues associated with making waste treatment a viable VOC emission control technique for hazardous waste management facilities. It discusses the waste streams of concern because of their volatile constituents and describes potentially applicable treatment techniques. The use of models for treatment process design is described. Finally, the paper discusses treatment cost, treatment residuals, and considerations of importance in choosing where in the life cycle of a hazardous waste stream to treat it.     

Sources and fate of nitrosodimethylamine and its precursors in municipal wastewater treatment plants.

To assess the occurrence and fate of nitrosodimethylamine (NDMA) and its precursors in wastewater treatment plants, samples from wastewater treatment plants and industrial sources were analyzed for NDMA, total NDMA precursors, and dimethylamine (DMA). The median concentration of NDMA in untreated wastewater was approximately 80 ng/L, with maximum concentrations up to 790 ng/L presumably occuring because of sources unrelated to domestic wastewater. Concentrations of DMA in untreated wastewater ranged from approximately 50 to 120 microg/L and accounted for a majority of the NDMA precursors. The removal of NDMA during secondary biological treatment exhibited considerable variability, with overall removal ranging from 0 to 75%. In contrast, removal of NDMA precursors and DMA generally exceeded 70%. The median concentration of NDMA in secondary effluent before disinfection was 46 ng/L. Although DMA was removed during secondary treatment, other NDMA precursors in wastewater effluent will result in formation of additional NDMA upon disinfection with chloramines.     

Effect of surfactant-coated iron oxide nanoparticles on the effluent water quality from a simulated sequencing batch reactor treating domestic wastewater

This study was conducted to evaluate the effect of commercially available engineered iron oxide nanoparticles coated with a surfactant (ENP_Fe-surf) on effluent water quality from a lab-scale sequencing batch reactor as a model secondary biological wastewater treatment. Results showed that ∼8.7% of ENP_Fe-surf applied were present in the effluent stream. The stable presence of ENP_Fe-surf was confirmed by analyzing the mean particle diameter and iron concentration in the effluent. Consequently, aqueous ENP_Fe-surf deteriorated the effluent water quality at a statistically significant level (p < 0.05) with respect to soluble chemical oxygen demand, turbidity, and apparent color. This implied that ENP_Fe-surf would be introduced into environmental receptors through the treated effluent and could potentially impact them.     

二沉池出水的电化学消毒试验研究

对德国威斯巴登城市污水处理厂和上海石化股份公司水质净化厂二沉池出水分别进行了电化学消毒试验。试验结果表明,用电化学方法对威斯巴登城市污水处理厂和上海石化股份公司水质净化厂二沉池出水进行消毒是可行的,消毒效果好,耗电少,杀菌率随电流、处理时间的增加而提高。     

The relevance of physicochemical and biological parameters for setting emission limit values for plants treating complex industrial wastewaters

The influents of plants treating complex industrial wastewaters from third parties may contain a large variety of often unknown or unidentified potentially harmful substances. The conventional approach of assessing and regulating the effluents of these plants is to set emission limit values for a limited set of physicochemical parameters, such as heavy metals, biological oxygen demand, chemical oxygen demand and adsorbable organic halogen compounds. The objective of this study was to evaluate the relevance of physicochemical parameters for setting emission limit values for such plants based on a comparison of effluent analyses by physicochemical and biological assessment tools. The results show that physicochemical parameters alone are not sufficient to evaluate the effectiveness of the water treatment plants for removing hazardous compounds and to protect the environment. The introduction of toxicity limits and limits for the total bioaccumulation potential should be considered to supplement generic parameters such as chemical oxygen demand and adsorbable organic halogens. A recommendation is made to include toxicity screening as a technique to consider in the determination of best available techniques (BAT) during the upcoming revision of the BAT reference document for the waste treatment industries to provide a more rational basis in decisions on additional treatment steps.     

Hazardous wastes and economic risk reduction: case study, Poland

A concise summary balance of industrial and hazardous waste is given, reflecting the situation in Poland. Nearly 130 million tonnes of waste were generated annually in the past in more than 1300 larger industrial plants. Approximately 1800 million tonnes of industrial waste is already stockpiled. The amount of hazardous waste generated per year was 0.3 and 1.0 million tonnes of the first and second class of toxicity, respectively. Seventeen existing on-site incinerators cannot treat the whole amount of solid and hazardous waste generated. Therefore, landfilling is still the most widely used method of waste disposal. Decontamination of the abandoned areas left by the Soviet Army, and reclamation of some hundreds of storage sites filled with outdated pesticides are now added to the national plan of waste management. Its implementation, including introduction of the best available and best managed technologies of hazardous waste treatment and disposal, will take at least 20 to 30 years.     

Case study I: application of the divalent cation bridging theory to improve biofloc properties and industrial activated sludge system performance-direct addition of divalent cations.

The objectives of this study were to examine the application of the divalent cation bridging theory (DCBT) to improve settling, dewatering, and effluent quality in pilot-scale reactors and a full-scale system treating an industrial wastewater. This was accomplished by lowering the monovalent-to-divalent (M/D) cation ratio by direct divalent cation addition. Research has shown that the M/D ratio is a potential indicator for settling and dewatering problems at wastewater treatment plants, and M/D ratios above 2 have been associated with poor settling, dewatering, and effluent quality. The M/D ratio of the wastewater in this study ranged from 6 to 20. The cations studied were calcium and magnesium. Results showed that the addition of calcium improved floc properties compared to control reactors with no calcium addition. The reductions in sludge volume index, effluent chemical oxygen demand (COD), and effluent total suspended solids (TSS) were approximately 35, 34, and 55%, respectively, when the M/D ratio was decreased to approximately 2:1. In addition, the cake solids from a belt filter press simulator increased by 72% and the optimum polymer dose required for conditioning was reduced by 70% in the reactor fed the highest calcium concentration when compared to control reactors with no calcium addition. The addition of calcium also decreased the negative effect of high filamentous organism numbers. In general, the addition of magnesium (Mg2+) had similar effects on effluent quality and dewatering properties, although some differences were measured. A full-scale test using calcium addition was performed. Measurements of effluent quality and floc properties were performed before, during, and after the calcium (Ca2+) addition period. The average M/D ratio during these periods was 6.2, 4.6, and 14.0, respectively. The addition of Ca2+ decreased the effluent five-day biochemical oxygen demand, effluent TSS, and effluent COD. The increased Ca2+ concentration also improved dewatering measured by a decrease in specific resistance to filtration and capillary suction time. Overall, the addition of divalent cations to the pilot- and full-scale activated sludge systems improved floc properties and the data fit well with the DCBT.     

Emission factors and sources of ethylene-diaminetetraacetic acid in waste water--a case study

Ethylene-diaminetetraacetic acid (EDTA) is a complexing agent and has the ability to form stable water-soluble complexes with metal ions. It is used in a variety of industrial applications including pulp and paper, metal, textile, leather rubber, pharmaceuticals, food, polymer production and others. Most of these applications are water based and lead to emissions into the waste water and reach sewage treatment plants. Industrial sources and municipal waste waters were monitored simultaneously. Mixed samples were taken over periods of one week at nine sample sites. The concentrations of EDTA were measured in waste water samples by gas chromatography using N-selective detection. The results showed that, although, the concentrations and loads were variable the paper manufacturing industry was the major EDTA contributor to the influent of the waste water treatment plant and contributed more than 98% of the total load. All the other sources including two household areas, were comparably low. In waste water of households concentrations between 10 and 70 microg/l EDTA could be detected. Concentrations of EDTA from different industrial waste water sources ranged from 28 up to 3980 microg/l. Influent and effluent concentrations of the WWTP were usually high in the range of 500-940 and 390-760 microg/l; respectively. Elimination rates averaged 15%, the calculation is based on emission loads. Specific emission factors were calculated based on population equivalents.     

Treatment of 2,4-D, mecoprop, and dicamba using membrane bioreactor technology

Phenoxyacetic and benzoic acid herbicides are widely used agricultural, commercial, and domestic pesticides. As a result of high water solubility, mobility, and persistence, 2,4-dichlorophenoxyacetic acid (2,4-D), methylchlorophenoxypropionic acid (mecoprop), and 3,6-dichloro-2-methoxybenzoic acid (dicamba) have been detected in surface and waste waters across Canada. As current municipal wastewater treatment plants do not specifically address chronic, trace levels of contaminants like pesticides, an urgent need exists for an efficient, environmentally friendly means of breaking down these toxic herbicides. A commercially available herbicide mix, WeedEx, containing 2,4-D, mecoprop, and dicamba, was subjected to treatment using membrane bioreactor (MBR) technology. The three herbicides, in simulated wastewater with a chemical oxygen demand of 745 mg/L, were introduced to the MBR at concentrations ranging from 300 μg/L to 3.5 mg/L. Herbicides and biodegradation products were extracted from MBR effluent using solid-phase extraction followed by detection using high-performance liquid chromatography coupled with mass spectrometry. 2,4-D was reduced by more than 99.0 % within 12 days. Mecoprop and dicamba were more persistent and reduced by 69.0 and 75.4 %, respectively, after 112 days of treatment. Half-lives of 2,4-D, mecoprop and dicamba during the treatment were determined to be 1.9, 10.5, and 28.3 days, respectively. Important water quality parameters of the effluent such as dissolved oxygen, pH, ammonia, chemical oxygen demand, etc. were measured daily. MBR was demonstrated to be an environmentally friendly, compact, and efficient method for the treatment of toxic phenoxyacetic and benzoic acid herbicides.     

Ultraviolet and chlorine disinfection of mycobacterium in wastewater: effect of aggregation.

Mycobacteria naturally aggregate in water, a characteristic that may serve to protect them against disinfection in wastewater. Secondary effluent was spiked with Mycobacterium terrae (M. terrae), sequentially filtered through 100-, 41-, and 20-microm nylon filters to partition aggregate sizes, confirmed using particle-size analysis and microscopy. Each sample was exposed to doses of UV light (10 to 60 mJ/cm2 at 254 nm) and free chlorine (27 to 150 mg-min/L at 4 degrees C). Inactivation of M. terrae in wastewater was initially rapid, with 2.5 log reduction at 14 mJ/cm2 and 56 mg-min/L for UV and free chlorine, respectively. However, in effluent and 100-microm filtered wastewater, spiked M. terrae was present to the highest doses evaluated. Interestingly, M. terrae passed through 41- and 20-microm filters were inactivated rapidly, with no survivors after moderate disinfection doses. Inactivation of Mycobacteria in wastewater may be compromised by aggregates larger than 41 microns.     

Medical Waste Disposal

Medical (biomedical) wastes pose numerous potential health and safety hazards. In addition to their infectious and toxic characteristics, the highly variable and inconsistent nature of medical waste streams has increased public concern about storage, treatment, transportation, and ultimate disposal.

In recent years, techniques have been developed to reduce human exposure to the toxic and infectious components of medical wastes. The most commonly used techniques include internal segregation, containment, and incineration. Other common techniques include grinding, shredding, and disinfection, e.g., autoclaving and chemical treatment followed by landfilling.

Of all the available technologies for medical waste treatment and disposal, incineration has been found to be the most effective method overall for destroying infectious and toxic material, volume reduction, and weight reduction in the medical waste stream, incineration destroys the broadest variety of medical waste constituents and can recover energy from the medical waste stream. Incineration also is an appropriate alternative to burial of human pathological remains.     

Decolorization does not always mean detoxification: case study of a newly isolated Pseudomonas peli for decolorization of textile wastewater

The textile industry is a favor to the Tunisian economy by offering several job positions. However, it’s not environmentally friendly. In fact, textile industries discharge high volumes of wastewater which contain several toxic pollutants such as dyes, fixator, and whiteness. In our study, Pseudomonas peli, isolated and characterized from Oued Hamdoun (center of Tunisia), was found able to decolorize textile effluent about 81 % after 24 h shaking incubation. On the other hand, the in vitro antiproliferative effects of the untreated and treated effluent was evaluated by their potential cytotoxic activity using the MTT colorimetric method against three human cancer cell lines (A549, lung cell carcinoma; HT29, colon adenocarcinoma; and MCF7, breast adenocarcinoma). Results showed that intact textile effluent and its content azo dyes didn’t inhibit the proliferation of all tested cell lines. However, the cytotoxic effect was remarkable when we tested effluent obtained after treatment by P. peli in a dose-dependent manner. This activity was attributed to the presence, in our treated effluent, of some azo products of dyes which are responsible for inhibition of human cell lines proliferation. Thus, the use of this strain for testing on the industrial scale seems impossible and disadvantageous.     

Biological treatment of gold ore cyanidation wastewater in fixed bed reactors

The treatment of a cyanidation effluent containing thiocyanate, free cyanide, and complexed cyanide was continuously performed for a period of 6 months. Activated carbon, pozzolana, and a mixture of pumice stone and zeolite were tested as supports in fixed bed reactors. Activated carbon adsorbed the different forms of cyanide. In contrast, the other supports did not remove any pollutants from the effluent during an adsorption experiment. All supports successfully allowed fixation of bacteria. More than 90% of the thiocyanate was biologically decomposed into NH4+, CO2 and SO4(2-), even when increasing the feed flow-rate and the pollutant concentrations. Free and complexed cyanides were eliminated, probably through a combination of precipitation and biological degradation. The oxidation of ammonium into nitrate was only performed by the activated carbon-containing column and with the more diluted feeding. The nitrification process was inhibited in all reactors when the cyanide concentrations and feed flow-rates were increased.     

电化学法消毒处理医院污水的试验研究

采用电化学法消毒处理医院污水,通过选用不同阳极材料构建的电化学体系,探讨电化学法的消毒机理.试验表明,以涂有贵金属(钌、铂和铱)氧化物的钛板作阳极,不锈钢板作阴极,在电流密度为8 mA/cm2、水力停留时间为15 min、空气流量为40L/h、极水比为1.0的试验条件下,消毒后污水中总大肠菌群数＜500 cfu/L,达到国家一级排放标准(GB8978-1996).     

Removal and formation of chlorinated triclosan derivatives in wastewater treatment plants using chlorine and UV disinfection

Triclosan, a common antimicrobial agent, may react during the disinfection of wastewater with free chlorine to form three chlorinated triclosan derivatives (CTDs). This is of concern because the CTDs may be photochemically transformed to tri- and tetra-chlorinated dibenzo-p-dioxins when discharged into natural waters. In this study, wastewater influent, secondary (pre-disinfection) effluent, and final (post-disinfection) effluent samples were collected on two occasions each from two activated sludge wastewater treatment plants, one using chlorine disinfection and one using UV disinfection. Concentrations of triclosan and three CTDs were determined using ultra performance liquid chromatography-triple quadrupole mass spectrometry with isotope dilution methodology. Triclosan and the CTDs were detected in every influent sample at levels ranging from 453 to 4530 and 2 to 98 ng L⁻¹, respectively, though both were efficiently removed from the liquid phase during activated sludge treatment. Triclosan concentrations in the pre-disinfection effluent ranged from 36 to 212 ng L⁻¹, while CTD concentrations were below the limit of quantification (1 ng L⁻¹) for most samples. In the treatment plant that used chlorine disinfection, triclosan concentrations decreased while CTDs were formed during chlorination, as evidenced by CTD levels as high as 22 ng L⁻¹ in the final effluent. No CTDs were detected in the final effluent of the treatment plant that used UV disinfection. The total CTD concentration in the final effluent of the chlorinating treatment plant reached nearly one third of the triclosan concentration, demonstrating that the chlorine disinfection step played a substantial role in the fate of triclosan in this system.     

污水紫外消毒微生物光复活原理及其控制技术

紫外消毒技术因其具有操作简单、无有害副产物、经济高效等优势,在污水处理中越来越广泛被应用.但其无剩余消毒能力,微生物在光照条件下进行修复而实现复活,从而导致出水微生物数量增多.综述了国内外紫外消毒出现的光复活现象,阐述了污水紫外消毒微生物光复活原理和控制技术.