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"What is the chlorine residual at your household tap?"

The answer may depend upon who is doing the sampling - and what answer they would prefer to see.

Any value from zero residual at the 'first draw' for your morning coffee to the distribution main's total residual can be recorded, depending on the volume of water drawn before sampling. Where household plumbing is flushed for three to five minutes before sampling, as recommended by the AWWA Committee on Bacteriological Sampling Frequency in Distribution Systems (1985), it is the distribution system main, and not the consumer's tap, which is being sampled.

Part of the reason your system might be purged before sampling is that it is always summer for your heated household plumbing. Warm temperatures encourage microbial growth, nitrification, oxygen depletion, chlorine depletion and, sometimes, corrosion of plumbing materials.

To purge microbial growth and their by-products, one is well-advised to run the water until it is as cool as the water in your water distribution main.

For the few that are interested in this microbially-mediated phenomena, the attached paper may explain why.


John Wiley & Sons, publishers of "Water Treatment Plant Performance Evaluations and Operations", 2009, has generously posted the following excerpts from this volume on their website, free for downloading.

The WTP Preface provides the outline and summarizes the 12 chapters of a volume created for water treatment plant operators and managers focussed on scientifically monitoring and improving plant process performance.

Perhaps of greatest scientific value in this release are the WTP Figures. This central element of the book provides 28 highly detailed, color micrographs of particles and organisms observed in water at various stages of collection and treatment. The descriptions accompanying each figure represent an attempt to put the information conveyed by each micrograph to practical operational use.

Appendix A (appA) describes the apparatus needed and basic procedures for conducting bacterial cell counts by epifluorescence microscopy.

Appendix B (appB) lists potential studies that a water utility might perform using microscopic particle analysis.

Appendix C (appC) starts with a discussion of operator responsibilities and operational data collection. This is followed by an extensive photographic tour of an operator 'making the rounds' to directly observe the functioning of the water treatment plant unit processes.




John O'Connor


Posted by John O'Connor Jul 16, 2015

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In the production of municipal drinking water, nothing is monitored more assiduously than turbidity.

Why is this so? Just what is turbidity? And why is this quality parameter so critical that it rates designation as a microbiological surrogate and primary drinking water standard?


Direct microscopic examination of drinking waters reveals that turbidity is caused by stuff - stuff that absorbs or scatters light. As you might imagine, light-scattering stuff may include silt, clay, cyanobacteria, precipitated carbonates, sulfides, metal oxides (e.g., rust and corrosion products), plant fibers and organic debris, microfloc, activated carbon 'fines', paint chips, nematodes, protozoans, cysts, bacteria, virus, ... (Oddly, while they may sometimes be present in large number, bacterial cells are so translucent that they contribute little to either the turbidity of natural - or treated drinking waters.)


The attached report, "The Effect of Lower Turbidity on Distribution System Water Quality", (AWWARF, 1993), includes analyses of sets of operational data from a broad range of major U.S. water utilities (Kansas City, MO; St. Louis, MO; St. Louis County (MO) Water Company; New Orleans, LA; Boston, MA; Baltimore, MD; New Haven, CT; Cleveland, OH; Louisville, KY; Dallas, TX; Phoenix, AZ; Oakland, CA; Los Angeles, CA; Metropolitan Water District of Southern California).  From this data, the seasonal relationship between each utility's treated ('finished') water turbidity and the frequency of recovery of total coliform and heterotrophic plate count (HPC) organisms in monitoring samples from the water distribution system could be determined.

Of special interest, a comparison of data from various utilities indicated a very distinct advantage in maintaining control over total coliform in the distribution system using chloramine as opposed to chlorine.

Attached is a listing of all posts to Water and Wastewater Slide Shows as of August 2015.

Some are for chemists, some for engineers, some for utility operators; all for downloading and use at your discretion.

We encourage your comments, especially if some of these posts have been helpful.

Kinetics of Chlorine Depletion and Microbial Growth in Household Plumbing Systems

Microscopy - for Water Treatment Plant Performance Evaluations


The Story of Bottled Water and other Slide Shows: iBook

Summary of Posts: 2010-2014

Bottled Water Exhibit: University of California-Davis (Video)

Water Chemistry

Water Softening by Precipitation with Lime

Taste and Odor Control at Bloomington, Illinois

Drinking Water Filtration: Replacement of GAC Caps at Bloomington, Illinois

What we can’t (or shouldn’t) put into our Sanitary Sewerage Systems

Anthropogenic Global Warming

A Drinking Water Supply Manifesto

20/20 (A video of 20 slides for 20 seconds each)

Control of Nitrification in a Water Distribution System

Air-Assisted Filter Backwash (Air Scour)

Virus in Water Supplies

Chlorine vs. Chloramine

Drinking Water Process Performance Evaluations

Total Organic Carbon - Health Effects

Total Organic Carbon Removal

Total Organic Carbon

Pharmaceuticals in Water and Wastewater

Wastewater Reclamation, Recovery and Reuse

Stream Biomonitoring

Methane in Ground Water

Household Electrical Energy Usage

Sustainability for Water Systems

Arsenic in Drinking Water

Pit Happens: Copper Corrosion in Household Plumbing

My Kitchen Tap versus My Refrigerator Dispenser

A Brief History of Human Waste Disposal - Part 6. The Future

A Brief History of Human Waste Disposal-Part 5. Wastewater Treatment

A History of Human Waste Disposal - Part 4. Sewage Treatment

A Brief History of Human Waste Management - Part 3: Sewerage

A Brief History of Human Waste Disposal - Part 2: Toilets

A Brief History of Human Waste Disposal-and its possible future.

The Story of Bottled Water

@The Sustainability Director of the University of California-Davis ran across my ACS 'Story of Bottled Water' presentation and wanted to create a display in the Student Union using my water bottles and slides. Thanks to him, I was able to clear out some space in my basement.

The attached video (m4v) of this display was appended to this post on July 19, 2015.

John O'Connor

Water Chemistry

Posted by John O'Connor Mar 13, 2014

Water Chemistry was developed as a primer for water and wastewater treatment plant operators. It introduced pC-pH diagrams for alkalinity and various acid-base systems encountered in natural waters. It illustrated the calculation of solubility of water treatment coagulants plus a number of USEPA-regulated metals. It provided sample data on removal of metals during wastewater treatment. It demonstrated oxidations and reductions of importance in water and waste treatment. It introduced the chemistry of carbon as viewed in water treatment regulations. It illustrated the chemistry of those well water sources influenced by microbial activity and reducing conditions in the ground - with an emphasis on the gases produced by microorganisms. It utilized bar diagrams to illustrate electroneutrality conditions. It provided previously unpublished data on the organic carbon content and occurrence of disinfection by-products (trihalomethanes) in Missouri drinking water sources and chlorinated supplies. It provided data on residual metals, hardness and sodium ions in finished drinking water supplies. It provided a unique set of data on the total bacterial cell counts enumerated in treated Missouri drinking waters.

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Water softening by precipitation with lime is widely practiced throughout the Midwestern United States. This slide show illustrates some of the treatment practices and classical equipment used by several municipal utilities.

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Algal blooms, followed by low lake water temperatures in the early winter of 2004, led to taste-and-odor producing compounds in the influent to the drinking water treatment plant at Bloomington, Illinois. The operational procedures adopted to mitigate the taste-and-odor along with extensive data on the presence and removal of geosmin and 2-methyl isoborneol (MIB) are presented in this slide show.


A major finding was that water recovered from the lime sludge storage lagoons contributed significantly to the plant influent geosmin/MIB concentrations.


Since most geosmin/MIB removal occurred primarily during filtration through Bloomington's GAC-capped filters, laboratory studies were undertaken to determine how rapidly geosmin adsorption capacity might change with GAC service age. These results indicated that adsorption on virgin carbon was most effective in geosmin removal. Despite increased colonization with microorganisms, GAC became progressively less effective after one and two years in service.


It was decided that virgin carbon should best be installed in the autumn in preparation for winter taste-and-odor challenges.

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On a rotating basis, over a three-year period, the granular activated carbon (GAC) caps on Bloomington, Illinois' 18 sand filters are replaced with virgin GAC. Microscopic examination of both the carbon and sand shows that extensive microbial colonization has occurred on the media.


Moreover, the GAC has changed markedly in size distribution. As 'fines' are lost and larger particles are reduced in size, GAC progressively occupies a narrower size range.

Everyone knows that we shouldn’t dry kittens in the microwave, but how many are aware of the many prohibitions communities have enacted to protect our sanitary sewerage systems and sewage treatment plant processes?

What can’t (or shouldn’t) we put in our toilets, sinks and household drains? Do most communities really prohibit us from emptying pool water or pumping out water from our flooded basements? Are there even ordinances against discharging ‘stinky stuff’?

After consulting the local regulations, we may be left wondering what we are permitted to put into our sanitary sewers.

Worse. In regions where treated wastewater is now destined to be an increasingly large part of our public water supply, prohibitions may get even more restrictive.

    Before joining in the national political sport of name calling, backbiting, and sloganeering, the first question that one should clinically address is: ‘are human activities responsible for the observed increases in world temperatures over the past century?’ There is no real question that the earth is warming. Some really competent members of the human race, now with the help of earth-orbiting satellites, have gotten very good at measuring temperature.



NASA: Goddard Institute for Space Studies

A manifesto, it turns out, is a statement of principles. Accordingly, it should address what principles should guide those who are responsible for the safety, security and long-term sustainability of our drinking water supplies. At first glance, most of these principles might seem simple, basic, even humble. Many of these principles have already been articulated by others in recent waterworks literature; they are commonly advanced in technical conferences; and they are undergirded by federal and state regulatory incentives.


However, there are impediments to both the adoption of and adherence to the seemingly most self-evident of principles. For example, in regions where water sources are deemed adequate to meet current and projected demands, calls for restraint and conservation may seem punitive both to water users and utility management. Since water utilities derive about three-quarters of their income from selling water, reductions in water use can only result in lost revenue. To water utility management, promoting restraints on water use is often regarded as akin to asking General Motors to sell fewer vehicles. For balance, revenue lost from any proposed water use reduction must be offset by a compensating rate structure adjustment for the utility. As for those profligate users in the community, equity requires that they be billed to pay the true costs associated with meeting their excessive demands.

John O'Connor


Posted by John O'Connor Apr 13, 2012

In Columbia, Missouri, our local independent movie theater group, the Ragtag, hosts (free to all attendees) a series of talks from a wide range of local people -- constraining them to show 20 slides, each for 20 seconds. Hence, "20/20". Obviously, the fast pace is a challenge for the speakers, but a guarantee for the audience that no presentation will last more than 7 minutes.


The youtube link, below, is to my son Tom's sub-7 minute presentation. Tom came to local attention as he reduced his electrical consumption, over a number of years, by 90%, solely by conservation. How? Tom keeps no secrets.


Why the bass solo? Tom elected to eliminate one of his slides.


Hope you enjoy the video presentation.


20/20 Columbia February 2012 - Tom O'Connor - YouTube

Copper Pipe Internal Corrosion.jpg

Having determined that chloramine disinfectant residuals were corroding copper in household plumbing, an effort was made to reduce the chloramine concentrations applied in the Willmar, Minnesota water distribution system. This involved controlling microbial-mediated nitrification, which led to the formation of nitrite during distribution. Nitrite ion, in turn, depleted the applied residual. Controlling the formation of nitrite then allowed less chloramine to be applied to the system.


This paper was presented at the Minnesota Chapter, American Water Works Association, in 1998.


A year later, after further trials of alternative methods, chlorite ion was adopted to control nitrification.

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