Disinfectant residual stability leading to disinfectant decay and by-product formation in drinking water distribution systems: A systematic review.

BACKGROUND
There is no consensus whether firefighters are at increased cancer risk for particular cancers. Previous studies have been small, mostly investigated cancer mortality, and suggested increased risks for brain, bladder, testicular, prostate, thyroid and colo-rectal cancers, leukemia, and melanoma.


METHODS
Records of all male cancers registered in California during 1988-2003 were obtained. Firefighters were identified from occupation and industry text fields. Logistic regression analysis used other cancers as controls.


RESULTS
Of the 804,000 eligible records, 3,659 had firefighting as their occupation. Firefighting was associated with testicular cancer (odds ratio = 1.54, 95% confidence interval: 1.18-2.02), melanoma (1.50, 1.33-1.70), brain cancer (1.35, 1.06-1.72), esophageal cancer (1.48, 1.14-1.91), and prostate cancer (1.22, 1.12-1.33).


CONCLUSIONS
Use of other-cancer controls and lack of an occupational history may have biased relative risks towards the null. However, this study, which contained more firefighter cancers than any previous epidemiologic study, produced evidence supporting some prior hypotheses.

Registry-Based Case-Control Study of Cancer in California Firefighters

This study investigated the bacterial regrowth in drinking water distribution systems receiving finished water from an advanced drinking water treatment plant in one city in southern China. Thirteen nodes in two water supply zones with different aged pipelines were selected to monitor water temperature, dissolved oxygen (DO), chloramine residual, assimilable organic carbon (AOC), and heterotrophic plate counts (HPC). Regression and principal component analyses indicated that HPC had a strong correlation with chloramine residual. Based on Chick-Watson's Law and the Monod equation, biostability curves under different conditions were developed to achieve the goal of HPC ⩽ 100 CFU/mL. The biostability curves could interpret the scenario under various AOC concentrations and predict the required chloramine residual concentration under the condition of high AOC level. The simulation was also carried out to predict the scenario with a stricter HPC goal (⩽ 50 CFU/mL) and determine the required chloramine residual. The biological regrowth control strategy was assessed using biostability curve analysis. The results indicated that maintaining high chloramine residual concentration was the most practical way to achieve the goal of HPC ⩽ 100 CFU/mL. Biostability curves could be a very useful tool for biostability control in distribution systems. This work could provide some new insights towards biostability control in real distribution systems.

Biostability in distribution systems in one city in southern China: Characteristics, modeling and control strategy

This article describes a kinetic model for nitrification in a drinking water distribution system. Monod kinetics were used to develop a steady-state plug-flow kinetics model to describe the variations of ammonia, nitrite, and nitrate-N concentrations in a chloraminated distribution system. Active ammonia-oxidizing bacterial and nitrite-oxidizing bacterial biomasses in the distribution system were determined using predictive equations within the model. The kinetic model used numerical analysis and was solved to predict ammonia, nitrite, and nitrate using C programming language for computers, which is similar to FORTRAN but simpler to use.

https://www.jstor.org/stable/info/41312581

Nitrification modeling in chloraminated distribution systems

Effectiveness of breakpoint chlorination to reduce accelerated chemical chloramine decay in severely nitrified bulk waters

/pdf/the-economics-of-firefighter-injuries-in-the-united-states-2dvl7yhuci.pdf

The economics of firefighter injuries in the United States

Biochemical nitrification was investigated in a large scale pilot study using aged galvanized steel, unlined cast iron and a hybrid pilot distribution systems consisting of a combination of aged polyvinyl chloride, lined cast iron, unlined cast iron and galvanized steel pipes. Variations of free ammonia, nitrate, nitrite, dissolved oxygen (DO) and chloramine residual in the distribution system water are discussed for each pipe material. Chloramine depletion, DO depletion, free ammonia release, heterotrophic plate count (HPC) growth, NO 2 –N and NO x –N measured as the sum of nitrite and nitrate N were dependent on pipe material. Galvanized steel pipe had the highest chlorine demand and produced conditions without residuals, which corresponded to the higher HPC proliferation and DO consumption and the lowest nitrification. The greatest production of nitrite and nitrate was observed in unlined cast iron pipe. Denitrification was observed in the unlined cast iron pilot distribution system following residual loss and development of anoxic conditions.

Water quality profiles during nitrification in a pilot distribution system study

The United States must learn how to cooperate with others if space research is to continue. The dilemma of the hypersonic plane is a case in point.

David C. Webb

Papers

The economics of firefighter injuries in the United States

Water quality profiles during nitrification in a pilot distribution system study

Hanging out for the hypersonic plane

Return from Orbit