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Waterline Spring 2007 (PDF: 749KB/8 pages)

Stew Thornley

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New Home for Metro School
After many years at the Thunderbird Hotel in Bloomington, the Metro District Waterworks Operators School will be moving to the Earle Brown Heritage Center in Brooklyn Center starting in 2007.

A sharp increase in meeting room costs at the Thunderbird made the move necessary. The 2007 school will be held from Wednesday, April 18 to Friday, April 20.

List of Speakers for AWWA Schools Being Updated and Expanded
The Minnesota AWWA Education Committee is updating and expanding its list of potential speakers for waterworks operators schools around the state.

Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great.

—Mark Twain

Biological Filtration Used in New Hutchinson Water Plant

Hutchinson Water Plant
The new Hutchinson plant, under construction in December 2006.

Biological processes have long been a staple in the treatment of wastewater, which is often aerated to stimulate bacteria and other organisms that consume most of the waste materials.
The same technology is available for drinking water, but one of the biggest impediments to its implementation has been the public’s perception of the process.  “Put bugs in our drinking water?” is a typical reaction, according to Eric Meester, an engineer with Earth Tech, Inc. of Plymouth, Minnesota. 
Meester added that the longtime success of chemicals for drinking-water treatment is another reason for resistance to alternative technologies.  “The success of chemical treatment has been documented for a long time. Biological removal has occurred naturally for longer, but no one looked for it or [questioned] why it existed.”
It was this discovery in Hutchinson, a central Minnesota city with approximately 14,000 residents, that helped lead to the decision to incorporate biological treatment for its new water treatment plant, scheduled to go on-line in March of 2007.
Hutchinson’s water system has consisted of five wells feeding an iron-removal plant that is divided into two treatment trains called the East Plant and West Plant.  Part of the original facility when it was constructed in 1960, the East Plant has been used only during period of high demand since a 1983 addition, known as the West Plant. 
The city was puzzled by the higher chlorine demand that occurred when they used the East Plant.  Working with Earth Tech, the city discovered that its groundwater had naturally occurring ammonia, which was creating the higher chlorine demand.  Further investigation revealed why the ammonia was an issue only in the East Plant.
The East Plant has a conventional filter, which is backwashed with treated (chlorinated) water, which reduces the possibility of biological activity.  The West plant has a Greenleaf filter, a rapid-gravity filter based on siphon-control, rather than valve-control, technology.  “The way it’s constructed,” explained Hutchinson water system supervisor Dick Nagy of the Greenleaf filter, “it uses its own backwash water.  It’s set up into four cells, so you use the effluent from the other three cells to backwash the fourth, and that’s not chlorinated.”
Nagy added that the West Plant has higher levels of dissolved oxygen (D. O.).  “The way the Greenleaf filter works, the water cascades over this weir, falls into this chamber, and goes into the filters.  It seems to be creating its own higher levels of D. O. in the water.”
The conditions in the West Plant, it was found, created natural biological nitrification, which was reducing the ammonia.
These discoveries, said Nagy, “set off the whole chain of events.  As time went on, we had to find a way to deal with the ammonia, and some other issues started coming up like corrosiveness and meeting the copper limit [the city has been in exceedance of the action level for copper], the aging of the infrastructure, and the plant itself, creeping up on our maximum design [limits], not being able to produce enough water.”

Schematic of the Hutchinson plant
The new Hutchinson plant, under construction in December 2006.

In looking at a new plant, the city considered biological filtration as it explored options to reduce both ammonia and iron as well as address the issues with corrosion.  “We figured we’ve got biological treatment now, there shouldn’t be a reason we can’t do it intentionally,” said Nagy, adding that they considered a complete biological facility but had to abandon that plan since it wouldn’t deal with the corrosiveness.

“We figured we’ve got biological treatment now,
there shouldn’t be a reason we can’t do it intentionally.”

 Reverse osmosis (R. O.) was considered since it would remove the iron and ammonia as well as soften the water, which would allow for adjustment in the pH and reduce corrosion.  However, Nagy said the expense of a complete R. O. system didn’t make sense.  “R. O. would have killed the bird with one big stone—more than what was needed.”
Finally, the city settled on a holistic approach to produce a blend of water that would be treated with biological filtration for the iron and ammonia and reverse osmosis for the corrosiveness.

East train of Hutchinson plant
West train of Hutchinson plant
Left: the East Plant of the existing system. Right: The West Plant, where natural biological nitrification has been taking place.

The water coming into the plant will be split with approximately 75 percent going through the reverse-osmosis membranes; the remainder of the raw water will go through the biological process, consisting of seven sand filters, the first two for iron and manganese and the others for ammonia.  Meester says the objective is “to provide an environment conducive for the biological activity.”
The amount of oxygen provided to create that environment differs between the filter for iron and the filter for ammonia and manganese.  In the iron filter, aeration will be controlled to provide just enough oxygen for biologically mediated oxidation to occur but not enough to chemically oxidize the iron. 
Meester explained that iron oxidation occurs faster biologically than chemically with the right oxygen conditions.  “You provide an environment so the bacteria, not the chemicals, oxidize the iron.  It’s based on a rate of reaction.”
The ammonia differs from iron in that this process requires higher oxygen concentrations for biological oxidization.  Because of this, in the filter for ammonia and manganese, aeration will be controlled to maximize the dissolved oxygen concentration to encourage the nitrifying bacterial growth.  Under oxygenated conditions, the nitrifying bacteria oxidize to nitrite and then to nitrate, which will be at a level of 1.5 parts per million, well below the maximum contaminant level for nitrate.
“You put the right conditions across the media,” said Nagy, “and the bacteria will grow and flourish in that media and convert the ammonia to nitrate, and then it’s a simple chlorination process after that.”
The $14 million project includes the new plant—which will nearly double the utility’s capacity, from 3.5 million to 6.5 million gallons per day—along with one new well and a 1.5 million gallon above-ground reservoir.

Construction started in April 2006.  The plant is scheduled to go on-line in March 2007.

Reverse-osmosis membranes
Dick Nagy in front of filters for biological filtration
The reverse-osmosis system, at left, in the new plant has three skids with 30 tubes on each. It is a two-stage system with 20 vessels in the first-stage and 10 in the second. At right is Dick Nagy by the newly installed filters for the biological nitrification.

Rules Update: Stage 2 DBP and LT2 ESWTR
Most of the Waterline readership is at least lightly familiar with the United States Environmental Protection Agency (EPA) Stage 2 Disinfectants and Disinfection Byproducts Rule (Stage 2 DBPR) and Long Term 2 Enhanced Surface Water Treatment Rule (LT2 ESWTR), which were signed on December 15, 2005. The rules strengthened protections against microbial contaminants, especially Cryptosporidium, and potential health risks of disinfection byproducts. They also included significant and immediate “early implementation” public water system (PWS) monitoring requirements. The beginning of a new year provides a good chance to remind you of the impending requirements and timelines, as well as the tools that are intended to make these regulatory obligations as painless as possible.

Stage 2 Disinfection Byproducts Rule
The Stage 2 DBPR affects all community water systems (CWS)—both surface and groundwater—and nontransient noncommunity water systems (NTNCWS) that produce and/or deliver water that is treated with a disinfectant other than ultraviolet light. That means that all parts of an interconnected PWS network (combined distribution system), including consecutive systems, will complete their regulatory steps in unison. However, compliance sampling is population-based and will require larger systems, when applicable, to conduct more extensive rule-related planning and sampling.

Minnesota CWSs are following the pre-compliance planning and monitoring schedules (shown in the accompanying tables). The Stage 2 DBPR will prompt systems with any recent (post-2004 or post-2005, depending on system size) DBP results greater than half the maximum contaminant level (40 micrograms per liter for total trihalomethanes, 30 micrograms per liter for haloacetic acids) to conduct Initial Distribution System Evaluation (IDSE) sampling. Fortunately, nearly all Minnesota CWSs do not fall into such a category and will instead be issued a waiver of IDSE requirement known as 40/30 Certification. MDH will generate and distribute 40/30 Certifications and will review all IDSE submissions (Standard Monitoring Plans or System Specific Studies). MDH will return IDSE Standard Monitoring Plan review decisions to CWSs within nine months of their submission deadlines (as reflected in Table 1). IDSE Standard Monitoring involves 12 sampling months. IDSE Standard Monitoring and System Specific Studies are simply tools that allow for the selection of the most appropriate Stage 2 DBP Rule health regulation sites. Operators of CWSs with DBP issues should already be refreshing their knowledge of distribution system features such as storage tanks, pressure zones, system interconnections, large watermains, and dead-end locations.

Due to the pre-compliance nature of the IDSE and source water monitoring, most affected PWSs need to submit some material directly to EPA. Fortunately, EPA has developed computerized data collection and analysis applications. The Data Collection & Tracking System (DCTS) allows PWSs, laboratories, and MDH to submit data through a central account on the Central Data Exchange (CDX) site at EPA. The DCTS is able to collect nearly all required information from any registered PWS user. However, registration of an “administrative user” under a PWS CDX account is a mandatory, and easily mishandled, first step in this process.

Table 1. Minnesota Stage 2 DBPR schedule deadlines

Minnesota CWSs
40/40 Certification or Submit SM Plan/SSS Begin IDSE Complete IDSE Submit IDSE Report
1. > 99,999 and consecutives October 1, 2006 July 1, 2007 June 30, 2008 October 1, 2008
2. 50,000-99,999 and consecutives April 1, 2007 January 1, 2008 December 31, 2008 April 1, 2009
3. 10,000-49,999 and consecutives October 1, 2007 July 1, 2008 June 30, 2009 October 1, 2009
4. < 10,000 and consecutives April 1, 2008 January 1, 2009 December 31, 2009 April 1, 2010

Long Term 2 Enhanced Surface Water Treatment Rule
The LT2 ESWTR requires compliance by all Subpart H (those that use a source that is surface water or ground water under the direct influence of surface water) PWSs.  Finally, compliance deadlines are based on the sizes of PWSs and are staggered from larger population to smaller population.

Minnesota surface water systems are developing source water monitoring plans and schematics, gathering past Cryptosporidium data for “grandparenting,” and developing sampling schedules according to the timelines in Table 2.  MDH is reviewing all submissions and coordinating sample materials and analyses with the MDH Laboratory and contract laboratories as necessary. Cryptosporidium sampling, with simultaneous E. coli sampling and turbidity analyses, is conducted during the first and third weeks of any month during the PWS’s 24-month Cryptosporidium sampling period.  Small systems (those serving no PWS with 10,000 or more people) are only required to conduct 12 months of bi-weekly E. coli sampling beginning October 1, 2008.

Table 2. Minnesota LT2 ESTWR schedule deadlines

Minnesota PWSs
Source Monitoring Schedule Begin Monitoring Comply with Cryptosporidium Treatment Requirements
1. Surface Water > 99,999 July 1, 2006 July 1, 2007 April 1, 2012
2. Surface Water 50,000-99,999 January 1, 2007 January 1, 2008 October 1, 2012
3. Surface Water 10,000-49,999 January 1, 2008 July 1, 2008 October 1, 2013
4. Surface Water < 10,000 July 1, 2008 January 1, 2009 October 1, 2013*

*October 1, 2014 if required follow-up Cryptosporidium sampling occurs

Fear not, computerless water operators! EPA has designated an Information Processing and Management Center (IPMC) for non-DCTS submissions. The IPMC is accessible through e-mail as well as the U.S. Postal Service and FAX transmissions. MDH will begin extensive efforts in 2007, primarily through water operator schools and PWS meetings, to instruct and assist smaller systems (less than 50,000 people) with EPA-collected submissions.

For Stage 2 DBPR and LT2 ESWTR:
U.S. EPA Stage 2 / LT2 - IPMC
P.O. Box 98
Dayton, OH 45401
FAX: 937-586-6557
E-mail: stage2mdbp@epa.gov

For questions about the Stage 2 DBP rule, contact David Rindal at 651-201-4660; for questions about the LT2 ESWTR, contact Lih-in Rezania at 651-201-4661.

Did You Know . . .
“Stewardesses” is the longest word typed with only the left hand and “lollipop” with your right?

“Typewriter” is the longest word that can be made using the letters on only one row of the keyboard?

No word in the English language rhymes with month, orange, silver, or purple?

“Abstemious” and “facetious” are the only words in the English language with all five vowels in order?

There’s no Betty Rubble in the Flintstones chewable vitamins?

Upcoming water training.


Updated Wednesday, October 14, 2015 at 08:43AM