Author: Fei Feng
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Previous studies have reported that biofilm extracted from full-scale biofilters can serve as nitrogenous disinfection by-product (N-DBP) precursors. Detached biofilm could escape during filter ripening and form N-DBP upon chloramination. This study examined the potential breakthrough of biofilm and N-DBP precursors during filter ripening at two water treatment plants (WTPs). The presence of biofilm was estimated by total adenosine triphosphate levels (tATP); N-DBP formation potential (FP) tests were conducted to quantify N-nitrosodimethylamine (NDMA) and haloacetonitrile precursors. While tATP peaks in filter effluent were observed post backwash at both WTPs, temporary increases of effluent NDMA FP were only observed during filter ripening where particle-associated NDMA precursors served as the dominant contributor. Overall, biofilters examined in this study demonstrated a consistent removal of NDMA FP regardless of the filter ripening process.
Author: Caroline Di Tommaso
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Biofiltration can be effective for disinfection by-product (DBP) precursor control, however few studies have considered its role in the potential formation of DBPs. The objective of this study was to determine the contribution of biofilm-related materials to form nitrogen-containing DBPs upon chloramination and to determine the influence of cyclical biofilter operation on DBP precursor removal. Biologically active media was sampled from a full-scale biofilter operating under cold-water conditions (3.6 ± 0.5°C) and its components were extracted with a cation exchange resin into a phosphate buffering solution. N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN4) formation potential tests conducted on extracted biofilm yielded 0.80 ± 0.27 ng NDMA/g media and 18.7 ± 3.3 ng dichloroacetonitrile (DCAN)/g media. However, an analysis of NDMA formation potential and biological surrogates in the effluent of a full-scale cyclically-operated biofilter did not show release of NDMA precursors during filter start-up after stagnation periods of 6 hours or more.
Author: Mehrnaz Mirzaei Barzi
Publisher:
ISBN: 9780494437469
Category :
Languages : en
Pages : 210
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Over the past century chlorine has been a reliable disinfectant to reduce transmission of waterborne diseases in drinking water. Concerns about chlorination have increased since it was discovered in the 1970s that use of chlorine in drinking water produces trihalomethanes (THMs), when chlorine reacts with natural organic matter (NOM), which has been observed in increased levels in surface water during the past decades. THM and other disinfection by-products (DBPs) such as some of the haloacetic acids (HAAs) and some nitrosamines are considered probable human carcinogens by USEPA. Since DBPs are still formed even when using alternative disinfectants such as chloramines, treatment processes by which disinfection by-product precursors are removed continue to be studied. Many researchers have demonstrated that the use of pre-ozonation/biological processes in the production of drinking water has the potential to decrease levels of disinfection by-products in finished water more than conventional treatment alone. Two of the parameters which affect the efficiency of DBP precursor removal in biofilters are filter media and filter flow rate. In this research, the biofiltration process was examined using pilot-scale filters receiving ozonated water to determine the relative effectiveness of these parameters for influencing the removal of natural organic matter. The research presented in this thesis initially focuses on determining the effects of flow rate and filter media including GAC (granular activated carbon) and anthracite on decreasing the levels of THM, HAA and nitrosamine precursors in biologically active filters. In the second part, the performances of full-scale and pilot-scale filters at the Mannheim Water Treatment Plant were compared. THM and HAA precursor removal was found to decrease when loading rates were increased, likely due to associated shorter contact times in the filters. Also, higher THM and HAA precursor removal was always observed in the GAC filters than in the anthracite filters. However, removal of nitrosamines was not affected by flow rate or the type of filter media. In general, the pilot-scale filter performance was representative of full-scale filter performance, especially in regards to THM precursor and chlorine demand removal. Statistical evaluation and interpretation of the data for HAA and NDMA precursor removal was more difficult, likely due to the low concentrations of these DBPs which was near their method detection limits (MDLs) and also because of some operational problems with pilot filter #1. Despite these limitations, the results of this study add to the literature concerning the use of different types of media to support biofiltration and reduce DBP precursor concentrations during drinking water treatment.
Author: Vivek Aditya Nemani
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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This research examined operational efficiency and performance enhancement of passive and engineered biofiltration. Pilot studies were carried out to evaluate the impact of backwash frequency, empty bed contact time, and nutrient enhancement on biofiltration systems treating different source waters (Lake Ontario and Lake Simcoe). Performance was evaluated in terms of organic carbon, ultrafiltration foulant (biopolymer), and disinfection-by product precursor removal. Increasing empty bed contact time from 4 to 8 min enhanced organic carbon degradation, while there was no statistically significant impact on biopolymer removal. Extending filter run time beyond 15 days had a detrimental effect on turbidity; however, no significant impact was observed in the monitored parameters when biofilters were backwashed every 10 days, which would result in economic benefits. Phosphorus addition (0.3 mg/L) improved organic carbon and disinfection by-product precursor removal, while nitrogen addition (0.8 mg/L) had no significant impact in spite of being consumed entirely through the biofilter.
Author: Yuefeng Xie
Publisher: CRC Press
ISBN: 0203486919
Category : Technology & Engineering
Languages : en
Pages : 180
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Book Description
The EPA has established regulations which classify four types of disinfection byproducts - TTHMs, haloacetic acids, bromate, and chlorite - and requires public water systems limit these byproducts to specific levels. Most of the information required to comply with these standards is either scattered throughout the literature or derived from confere
Author: Daniel Logan McCurry
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Disinfection of potable water is one of the great public health victories of the twentieth century, responsible for the avoidance of millions of deaths due to waterborne illness. However, application of disinfectants, typically chemical oxidants, leads to formation of hundreds of trace contaminants, often carcinogens, and consumption of chlorinated water has been epidemiologically linked to bladder cancer and certain birth defects. Eleven of these compounds are federally regulated in drinking water, but certain non-regulated disinfection byproducts (DBPs) are orders of magnitude more toxic than currently regulated compounds. Two specific DBPs, chloropicrin and N-nitrosodimethylamine (NDMA), are especially genotoxic, and are associated with nitrogen input into drinking water supplies. Wastewater-impacted drinking water and recycled wastewater are enriched in the precursors of these compounds, and their formation during potable water treatment is likely to grow, as wastewater increasingly contributes to the water supply. This thesis focuses on applying the tools of environmental organic chemistry to identify the chemical precursors and formation mechanisms of these compounds, leading to strategies for their control during water treatment. In particular, ozonation of primary and secondary amine compounds, leading to formation of nitro compound intermediates, was found be responsible for chloropicrin formation during water treatment. Secondary N-methylamines and primary amines geminal to facile leaving groups were particularly potent precursors, forming chloropicrin at up to 50% yield when exposed to ozone followed by chlorine. Based on this predominant formation pathway, chloropicrin precursors may be oxidized upstream of ozone addition to prevent chloropicrin formation. Strategies for controlling NDMA formation, a major concern during wastewater recycling, were developed based on an understanding of the chemical composition of NDMA precursors, and chloramines, the primary disinfectant applied during wastewater reuse. Minor modifications to wastewater recycling operations, in particular switching from low-pressure to medium-pressure mercury lamps for ultraviolet light treatment, and minor adjustments in the application of chloramines, were shown to dramatically reduce NDMA concentrations in final effluent. Finally, the effluent from a new, all-anaerobic wastewater treatment system was demonstrated to more efficiently remove trace contaminants and DBP precursors than conventional aerobic treatment, suggesting that this energy-saving technology may also be more suitable for water reuse than conventional treatment. These findings facilitate reducing the chronic health risk associated with consumption of (intentionally or unintentionally) recycled wastewater.
Author: Baiyang Chen
Publisher:
ISBN:
Category : Drinking water
Languages : en
Pages : 764
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Author: Philip C. Singer
Publisher:
ISBN:
Category : Medical
Languages : en
Pages : 456
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Book Description
Written by more than 30 DBP experts, this technical and managerial reference tool provides essential background and addresses recent activities of the EPA and environmental consultants. It answers important questions, such as how to balance microbial and chemical risks, and includes information on new regulation and treatment costs.
Author: Nurul Mokhtar Kamal
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: William A. Mitch
Publisher:
ISBN: 9781605730530
Category : Water
Languages : en
Pages : 186
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