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The removal of ammonia, arsenic, iron and manganese by biological treatment from a small Iowa drinking water system.

ABSTRACT: Although not regulated in United States drinking water, ammonia has the potential to increase chlorine consumption and cause nitrification problems in the distribution system. Many groundwaters with elevated ammonia are also contaminated with other inorganic analytes such as arsenic, iron, and manganese, all of which have primary or secondary maximum contaminant levels (MCLs). The objective of this work was to demonstrate the effectiveness of an innovative biological treatment process to simultaneously remove ammonia (2.9 mg N per L), arsenic (23 μg L^-1), iron (2.9 mg L^-1) and manganese (80 μg L^-1) from a groundwater source in Iowa. The biological treatment system consisted of an "aeration contactor" followed by a conventional granular media filter. Orthophosphate was also added, as a biological nutrient, at 0.3 mg PO₄ per L. Ammonia, manganese, and iron were consistently reduced through the pilot system by 98 to 99%. Complete oxidation of ammonia to nitrate was observed (i.e., no nitrite was released) and arsenic was consistently removed to below the 10 μg L^-1 MCL. Ammonia was oxidized by ammonia and nitrite oxidizing bacteria and arsenic by bacteria which converted As(III) in the source water to more readily removable As(V). Iron was presumably oxidized by oxygen during aeration although some biologically assisted oxidation could not be ruled out. As(V) bound iron particles were removed in the filter resulting in effective arsenic (and iron) reduction. A surprising treatment benefit was the effective manganese reduction, the mechanism of which was not so clear, but was attributed to biologically assisted oxidation of Mn(II). While some system acclimation time was necessary to achieve desired ammonia and manganese reductions, acceptable arsenic and iron reductions were observed shortly after start-up.

SUBMITTER: Lytle DA

PROVIDER: S-EPMC7898138 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Nitrate is a drinking water contaminant arising from agricultural sources, and it is a precursor in the endogenous formation of N-nitroso compounds (NOC), which are possible bladder carcinogens.We investigated the ingestion of nitrate and nitrite from drinking water and diet and bladder cancer risk in women.We identified incident bladder cancers among a cohort of 34,708 postmenopausal women in Iowa (1986-2010). Dietary nitrate and nitrite intakes were estimated from a baseline food frequency questionnaire. Drinking water source and duration were assessed in a 1989 follow-up. For women using public water supplies (PWS) > 10 years (n = 15,577), we estimated average nitrate (NO3-N) and total trihalomethane (TTHM) levels and the number of years exceeding one-half the maximum contaminant level (NO3-N: 5 mg/L, TTHM: 40 ?g/mL) from historical monitoring data. We computed hazard ratios (HRs) and 95% confidence intervals (CIs), and assessed nitrate interactions with TTHM and with modifiers of NOC formation (smoking, vitamin C).We identified 258 bladder cancer cases, including 130 among women > 10 years at their PWS. In multivariable-adjusted models, we observed nonsignificant associations among women in the highest versus lowest quartile of average drinking water nitrate concentration (HR = 1.48; 95% CI: 0.92, 2.40; ptrend = 0.11), and we found significant associations among those exposed ? 4 years to drinking water with > 5 mg/L NO3-N (HR = 1.62; 95% CI: 1.06, 2.47; ptrend = 0.03) compared with women having 0 years of comparable exposure. TTHM adjustment had little influence on associations, and we observed no modification by vitamin C intake. Relative to a common reference group of never smokers with the lowest nitrate exposures, associations were strongest for current smokers with the highest nitrate exposures (HR = 3.67; 95% CI: 1.43, 9.38 for average water NO3-N and HR = 3.48; 95% CI: 1.20, 10.06 and ? 4 years > 5 mg/L, respectively). Dietary nitrate and nitrite intakes were not associated with bladder cancer.Long-term ingestion of elevated nitrate in drinking water was associated with an increased risk of bladder cancer among postmenopausal women. Citation: Jones RR, Weyer PJ, DellaValle CT, Inoue-Choi M, Anderson KE, Cantor KP, Krasner S, Robien K, Beane Freeman LE, Silverman DT, Ward MH. 2016. Nitrate from drinking water and diet and bladder cancer among postmenopausal women in Iowa. Environ Health Perspect 124:1751-1758;?http://dx.doi.org/10.1289/EHP191.

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The removal of ammonia, arsenic, iron and manganese by biological treatment from a small Iowa drinking water system.

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