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Cross Connection Forum—Cross Connection - What is it?

By Doug Dolan

Consumers can expect the water provided to them by their water supplier to be pure and healthful. Water suppliers across Canada spend millions of dollars to purify and treat water before it is delivered to the consumer. However, many consumers are not aware that the water supplier can also expend great effort to protect the water from the possibilities of contamination or pollution while it flows through the distribution system within a building.

Water distribution systems are designed with the intention of the water flowing in a certain direction from the distribution system to the consumer. However, hydraulic conditions within the system may deviate from the "normal" conditions, causing the water to flow in an "opposite direction" in unprotected systems. This occurrence is called "backflow".

There are two types of "backflow" that occur within plumbing and water distribution systems. The first we shall call "Backsiphonage". Backflow occurs when the pressure in the distribution system drops, siphoning water from the consumers distribution system within a building, into the distribution of the supplier. A great example of this takes place during a fire. For example, during fire fighting, or when a water main in the street breaks, water is "sucked" to the point of high usage, possibly drawing non-potable substances with it, filling the distribution lines with these substances. A hose filling a swimming pool that is immersed in the half filled pool, can draw the treated water in the pool back into the suppliers distribution system when the main pressure becomes less than that of the building supply side.

The second type of backflow we shall call "backpressure". This kind of backflow occurs when the building distribution system pressure exceeds that of the suppliers side, thus the unprotected line is "pumped" into the suppliers system. A good example of this would be a pressure washer with chemical injection, when the conditions are right, a pressure of 2000 psi can be obtained within the process.

These conditions we have discussed are called "Cross Connections". To simply define what a cross connection is, can be easily said: "Any actual or potential connection between a potable (drinking) water system and any source of pollution or contamination is a cross connection."

Because of these potential dangers to the water consumer, it is necessary to control cross connection. It is also necessary to educate the consumer about cross connections, backflow and backflow devices, and cross connection control programs. In the next WATERMARK, we shall discuss these topics in greater detail.

Examples of a cross connection to the potable water system are:

What are some Documented Hazards?

Farming family: stomach cramps, diarrhea, vomiting, and oral anesthesia
Cause: In-line stock dispenser adding supplement to cattle trough through water feed line. Had been inter-connected to farm cottage potable supply.

Hotel: foaming soap-like bubbles coming from the cold water supply at the kitchen, resulting in shocking-tasting water
Cause: Soap dispenser was connected to the domestic supply line.

Fire Brigade: complaint that the water supply changed colour while dousing out a plastics fire
Cause: The fire truck started up the booster pump, thus drawing excess water from the main and causing a reverse action to the supply line, drawing paint from a mixing vat in a paint factory two premises down the road.

Private residence: grass clippings in toilet bowl and kitchen sink
Cause: compost bin in the yard had a garden hose left running in it, and when the mains supply was cut, a negative pressure resulted in backflow to the dwelling.

Factory: green slime and globbly things came out of the tap
Cause: Head tank did not have an adequate air gap separation and the valve was under water.

Factory: complaint of air entering the water supply and poor water pressure
Cause: A cross-connection to the cooling jacket on an air compressor in a nearby panel beating repair shop resulted in a direct connection to the inner jacket and holding tank, thus letting air into the system.

Racecourse: funny-tasting water and soft drinks at the post mix machine…metallic-tasting
Cause: The post mix dispenser was connected to CO2 gas from a cylinder. Debris had passed through the strainer, which was not a ball check valve.

Burst Water Mains: contractors on site found patches of foam and warm water-running through the open water main
Cause: Backflow from hot water cylinders and commercial dish washing machines in restaurants and high rise buildings.

Factory: 120 staff were sent home with stomach cramps, gastric complaints, and headaches...foul-tasting water
Cause: The factory processes newspaper in pulp, the tanks are filled with a mixture of alum and water from the domestic supply. A cross-connection occurred when an underwater inlet was installed during maintenance work on the internal plumbing.

Commercial Property: bad-tasting and smelly water
Cause: Tenant on the premise had a leaking tap, and couldn't contact the owner, so a garden hose was attached to the hose cock and stuffed down the sewer line. When the water main pressure was reduced, back siphonage occurred, causing sewer gases to enter the premise and water supply through the hose cock.

Restaurant: blue water at the sink and a funny smell
Cause: Toilet duck blocks had been put into the head tank feeding the WC facilities. The valves were under water; a cross-connection existed and resulted in the kitchen domestic supply being polluted.

Commercial Property (Multi-Storey Building): strange taste, smell, and black colour to the drinking water
Cause: One of the dual head pumps failed, the other one was disconnected, removed and breaching pipe work was installed. This was re-plumbed into the fire service by mistake resulting in back pressure whereby the contaminated firewater flowed in the drinking supply and surrounding area.

Restaurant: strange unidentified crystallised particles coming out of the cold faucet in the kitchen - had a strange smell and looked like tiny brown glass beads
Cause: A large coffee machine was connected to the boiler, creating pressurized boiling water which backflowed into the filter system, causing it to disintegrate. This formed a residue of calcium sulphate in resin beads, contaminating the drinking water.

Industrial Site: tenants complained of poor water quality - a strange taste and smell
Cause: Another tenant in the building had set up a commercial soft drink manufacturing plant. A cross-connection with the base material and drinking water resulted in the adjoining tenant's supply being contaminated.

Apartments: High rise units experienced hot water at their water meter
Cause: A negative pressure was caused during maintenance work on the public main, and hot water had back-siphoned from mains-pressure hot water cylinders. There was danger of these tanks imploding.

Wholesale Meat Processing Factory: employees complained of a funny taste in the lunch room water supply
Cause: The sausage machine used a hydraulic ram and bladder system to produce sausages. A cross-connection was found with the fire service line. When the preparation area was washed down using it, the pressure in the domestic line dropped resulting in back siphonage. Blood and other contaminants entered the water due to this.

Private Residence in a Basement Flat: strange taste in the drinking water
Cause: An improvised bidet in an upstairs flat had been constructed, using a small garden hose which was left lying in the toilet bowl when not in use. The owner of the building turned off the water supply, creating negative pressure resulting in back siphonage and a cross-connection with the sewer.

Motor Mechanic Firm (large trucks): workshop water was reported as having a diesel taste and smell coming from the taps in the staff lunchroom
Cause: A cross-connection to the oil bath was discovered in the diesel yard which resulted in a small amount of diesel being sucked into the water line when maintenance work was being carried out on the main in the street.

Numerous Private Residences: drinking water had odour/taste problems
Cause: WC cisterns had been interconnected to a hand-held shower head which had been used as a body wash (bidet) for ethnic religious customs, and left in the fitment when not in use.

Large Commercial Multi-Storey Complex: drinking water had diesel taste
Cause: Investigation revealed that the garden sprinkler heads had been contaminated with diesel and foreign matter. Service was immediately terminated, flushed and disinfected repeatedly. Renovations to the building were being carried out, the potable supply cut, which allowed a siphon effect back into the main line and pumped through the site.

Private Resident: green stringy weed in cold water faucet filter at the kitchen
Cause: Old garden hose lying in the yard full of green algae had been sucked back into the domestic supply when repair was being carried out at adjoining premises.

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CWWA - Highlights of 2000

CWWA has two principle missions: to be the national voice of the water and wastewater sector on federal and national legislative, policy and program initiatives; and to ensure a pan-Canadian information flow.

During the year the Association tracked, provided summaries, collected comments, and formulated and presented positions on 6 federal legislative initiatives:

Three of these, C-8, C-15 and C-31, are still active and likely to be resumed in the new Parliament.

CWWA also tracked the Canadian Council of Ministers of Environment implementation of the Harmonization Agreement and the development of Canada-Wide Standards - the most important being: Dioxins and Furans, Mercury, and Petroleum Hydrocarbons in soil.

The key regulatory activities of the federal government included the Canadian Environmental Protection Act assessments of: Aluminum Salts, Ammonia in the Aquatic Environment, Chloramines, Chloroforms, N-Nitrosodimethylamine (NDMA), Road Salts and Textile Mill Effluents; chloroforms and NDMA have been declared "CEPA" toxic. The others are most likely to be declared toxic. Once "toxic" Environment Canada is required to develop management instruments within 2 years. All are part of municipal discharges from water and wastewater treatment plants and storm sewers. Proposed Environmental Emergency Planning and Prevention of Pollution Planning Guidelines for "toxic" substances were reviewed and representatives of CWWA members attended meetings in Ottawa, Montréal, Halifax, Toronto, Vancouver and Calgary. Formal position papers were also submitted on these initiatives.

The Board of Directors met with senior Federal Officials twice to discuss these initiatives and municipal concerns. Representatives of CWWA and the member Associations participated in the Multilateral Stakeholders Wastewater Forum and Workshop in Ottawa January 15 to 18, 2001. Municipal wastewater effluents will be a focus of federal activities over the coming two years and the municipal sector will need to be actively involved in the discussions. CWWA will be the avenue into these discussions and needs the support of all municipal water and wastewater agencies in order to collect the greatest amount of expertise and experience and to ease the burden on those who are supporting the National voice. Endeavours will be made to let all municipal agencies know of developments and to collect their input, but the best way to support the Association is to join it. Contact CWWA by phone at (613) 747-0524, fax at (613) 747-0523, or by E-mail at admin@cwwa.ca. Visit the CWWA website at www.cwwa.ca and become part of the pan-Canadian water and wastewater sector's voice.

Note from Bob Jones, GVRD and the BC Director for CWWA: I would urge all BC water and wastewater utilities to join CWWA in order to learn what is happening in federal and national legislative, policy and program initiatives, to be able to contribute to the formation of the position that CWWA is expressing on those initiatives on behalf of all utilities, and to increase the strength of CWWA to form and present those opinions. Membership is corporate not individual and fees are calculated on the basis of population served. The fees which have not been increased since 1993 are also subject to 50% and 25% reductions in the first and second years. Join us in CWWA, there are many federal and national initiatives that are being taken that will impact on municipal activities even though we are also regulated by the province.

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AWWA Round Up

By Dennis Mitchell, AWWA Director

The Winter Board Meeting of the AWWA was held on January 20th and 21st. It is at this meeting that the future officers of the Association are elected by the Directors. Specifically, the President-Elect and five (5) Vice-Presidents are selected, with the successful President-Elect becoming President in two years. Two candidates ran for President-Elect, with Lyndon Stoval being successful. Lyn is currently an AWWA Vice-President and represents the South Carolina Section. He is the General Manager of the Greenville SC Water System.

Seven (7) candidates ran for the five (5) Vice-Presidential positions, and we were pleased to have Ken Brothers from the Atlantic Canada Section elected. The remaining Vice Presidents are: Yasser AbouAish - Minnesota Section; Dennis Leslie - Illinois Section (2nd term); Terry Rolan - North Carolina Section and Katie McCain - Texas Section (2nd Term). Katie will join us as the AWWA dignitary at the BCWWA Annual Conference in Penticton. All of these candidates were required to conduct a limited campaign, and deliver speeches to the Board prior to the vote.

Other highlights of the meetings included:

Water for People announced they will be issuing an Annual Award to recognize distinguished service to WFP. The "Kenneth J. Miller WFP Founders Award" will be issued for the first time at the 2001 AWWA Conference in Washington DC, in conjunction with WFP's 10th anniversary.

The Board approved the AWWA Utility Accreditation Program. This program will establish standards and formal recognition of accrediting bodies to promote improvements in water and wastewater utilities. CSA has agreed to participate in Canada so the program is getting off to a good start. I have a lot of information on this, so if anyone would like details, please contact me.

AWWA has initiated an e-business plan with an outside technology provider to offer utilities a no-cost e-market place for the water industry. Essentially, AWWA will "sponsor" a web site that allows Utilities to obtain goods and services from vendors "without the burden of any transaction or commission-based fees", to quote the AWWA Press Release. This business venture by the AWWA is generating a lot of discussion among Manufacturers and Suppliers, so if you have any comments or concerns about the venture, please let me know so I can carry them forward.

Every year at the AWWA Annual Conference and Exhibition (ACE), the Canadian Sections, through the Canadian Affairs Committee (CAC), sponsor "The Canadian Water Forum". The Forum is a very popular social evening for Canadian delegates and guests to meet and renew acquaintances. This year ACE will be held in Washington DC and the CWF will be held at the Canadian Embassy, on Monday June 18th. Everyone is quite excited about this; the only wrinkle is that for security reasons, we can only accommodate 350 people when we normally host around 400. So advance ticket sales will be your only way to get in. CAC will be issuing tickets and we have managed to secure 120 for BC. Please let me know if you want tickets, we will give first consideration to those that have supported BCWWA by purchasing these tickets in the past though.

I sit on the Ad Hoc Committee on Organizational Alliance, which is charged with developing guidelines which AWWA will follow in forming professional alliances. At our first meeting we established broad objectives and goals for the alliances to achieve. We will follow this up through email and meeting communication to have our report ready for the June ACE. I was pleased that a number of suggestions we made are being incorporated into the goals and objectives.

The Canadian Directors discussed the status of the new and existing water legislation now appearing across Canada, including the BC Safe Drinking Water Act. We agreed that the Canadian Sections should sit down as a group and compare all of the regulations being proposed, so we as an Association can speak informatively on the new regulations, as they are given to us for comment and input.

Many other interesting issues were discussed at the Meeting, so if you would like more information or details, please email me at dmitchell@umagroup.com.

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University Reports

The UBC Environmental program, within the Civil Engineering Department, offers many opportunities for conducting applied research projects. The following abstracts from our graduate students reflect the broad nature and progress of our research work. For more information, please contact Jim Zhou, University of British Columbia, by phone (604) 822-9126; fax: (604) 822-6901; or email: jpzhou@civil.ubc.ca.

Recovering Carbons from Sludge Digestion for Biological Nutrient Removal

Jowitt Li, Don Mavinic, and Harlan Kelly

Jowitt at a conference to present his work.

Biological nutrient removal (BNR) systems usually require the supplement of external carbons to enhance efficiencies of nitrogen and phosphorus removal. Many full-scale wastewater treatment plants implement carbon additions in order to ensure and optimize the performance of their BNR systems. Thermophilic Aerobic digestion (TAD) is operated at elevated temperatures to achieve pasteurization, and volatile solid destruction for sludge stabilization. Preliminary work showed that the accumulated volatile fatty acids in the supernatants of TAD sludge from micro-aerated operation, where the oxygen demand of a system exceeded the supply, was a potential carbon source for BNR enhancement.

The objective of this research work is to develop a new method using respirometric information obtained from a lab-scale BNR system to estimate available carbons in TAD supernatants, and to further optimize on-line carbon additions through assessing the performance of this real-time BNR system. This study has developed a carbon dioxide monitoring strategy to fulfill above multiple purposes, and has obtained promising results.

Energy Losses across Constructed Riffles and the Effect on Flood Levels

Dan Walker, Robert Millar, and Robert Newbury

Dan at his fieldwork site - Chapman Creek, Sechelt, BC

Riffle-pool sequences in gravel bed rivers create a range of hydraulic conditions that are important for providing and maintaining instream habitat. However, anthropogenic disturbances often result in a uniform, channelized reach devoid of the natural riffle-pool topography. Accordingly, the reintroduction of riffle-pool sequences has become an integral part of river restoration. Yet, in the absence of design guidelines, restoration has often lacked sufficient hydraulic analysis.

Of serious concern is the insufficient knowledge regarding energy losses across constructed riffles, and their corresponding effect on flood levels. This has particular relevance to riffle restoration in areas where increased flood levels cannot be tolerated. The objectives of the current research are to investigate energy losses across both "natural" and reconstructed riffle-pool sequences, and to develop a design procedure to predict the impact of riffle reconstruction on flood levels. This study will provide valuable insight to the design of channel restoration projects.

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