Water Quality Analysis

Constituents in green were NOT detected.  They are presented at the level in which detection is possible with available technology. Supplementary Information #Why are some concentrations different in the untreated vs. treated water

 

Portland Water District Analysis of Water Supplies (as tested on February 17, 2010, unless otherwise noted)
Constituent	Units	Greater Portland Untreated	Greater Portland Treated1	Gorham Booster  (Distribution)	Steep Falls Untreated	Steep Falls Treated1	MCL (for comparison only)2
Physical
Color	SU	<5	<5	<5	<5	<5	15
Conductivity	µS	52	75	76	222	248	**
Total Residue	mg/L	14	25	22	97	98	500
Turbidity	NTU	0.3	0.35	0.25	0.25	0.2	1
Inorganic Non-metals
Residual chlorine	mg/L	N/A	2.0	1.8	NA	NA	4.0
Alkalinity(as CaCO3)	mg/L	5.8	8.6	7.6	15.4	20.9	**
Dioxide	mg/L	1.8	0.7	0.8	16.7	1.3	**
Ammonia – N	mg/L	0.03	0.4	0.4	<0.02	<0.02	**
Nitrite – N	mg/L	<0.005	<0.005	<0.005	<0.005	<0.005	1
Nitrate – N	mg/L	0.1	0.2	0.2	0.8	0.8	10
Chloride	mg/L	7	9	9	42	45	250
Dissolved Oxygen	mg/L	15.4	16.3	16.5	8.8	11.9	**
Fluoride	mg/L	0.07	1.15	1.14	0.10	1.03	4
Hardness(asCaCO3)	mg/L	13	13	13	32	32	150
pH	SU	7.1	7.8	8.1	6.6	7.2	8.5
Silica	mg/L	2.7	2.9	3.1	8.4	8.1	**
Phosphorus	mg/L	NA	0.36	NA	NA	NA	**
Sulfate3	mg/L	NA	3	NA	NA	5	250
Inorganic Metals
Arsenic4	mg/L	N/A	<0.0005	N/A	N/A	<0.0005	0.05
Barium4	mg/L	N/A	0.0037	N/A	N/A	0.0065	2.0
Cadmium	mg/L	<0.0003	<0.0003	<0.0003	<0.0003	<0.0003	0.005
Calcium	mg/L	3.8	4	3.9	9	9.1	**
Chromium4	mg/L	NA	0.00058	NA	NA	0.00066	0.05
Copper	mg/L	<0.02	<0.02	<0.02	0.11	<0.02	1.3
Iron	mg/L	<0.05	<0.05	<0.05	<0.05	<0.05	0.3
Lead	mg/L	<0.002	<0.002	<0.002	<0.002	<0.002	0.015
Magnesium	mg/L	0.79	0.75	0.75	2.2	2.2	**
Manganese4	mg/L	0.0015	0.0016	0.0016	0.0036	0.0037	0.05
Mercury4	mg/L	NA	<0.00005	N/A	NA	<0.00005	0.002
Nickel4	mg/L	NA	<0.0005	NA	NA	<0.002	0.1
Potassium	mg/L	0.44	0.75	0.51	2.5	2.8	**
Selenium4	mg/L	N/A	<0.002	NA	NA	<0.002	0.05
Silver	mg/L	<0.0003	<0.0003	<0.0003	<0.0003	<0.0003	0.05
Sodium	mg/L	6.1	12.1	11.6	32	41	100
Zinc	mg/L	<0.02	0.1	0.11	<0.02	<0.02	5
Aggregate Organic
Carbon, total organic5	mg/L	2.6	2.4	NA	0.6	0.6	**
Pesticide/Herbicide6
	µg/L	NA	ND	NA	NA	ND
Asbestos7
(million fibers/L)	106f/L	NA	< 0.12	NA	NA	NA	7
Radionuclides
Gross alpha8	pCi/L	NA	0.117	NA	NA	5.48	15

 

Chlorine and pH vary throughout the distribution system so values at your tap may differ from this locale.  Also, iron, copper and lead can be affected by the condition of distribution pipes and interior plumbing.
² MCL= Maximum Contaminant Level. The highest level of a contaminant that is allowed or recommended in drinking water. 
³ Sulfate – Greater Portland analyzed in June 2009.  Steep Falls analyzed October 2008
⁴ Arsenic, barium, chromium, nickel, manganese, mercury and selenium analyzed in June 2009. Steep Falls analyzed June/October 2008.
⁵ TOC analyzed in December 2000.
⁶ Pesticide/herbicide analyzed in October 2008 (Gr. Portland) and August 2008 (Steep Falls).
⁷ Asbestos analyzed in June 2002 in Cumberland area.
⁸ Gross alpha analyzed in May 2006 
** - MCL does not exist for these constituents
NA – Not analyzed
ND – None detected

 

Why are some concentrations different in the untreated vs. treated water?

Constituent concentrations in the raw, untreated water are extremely stable throughout the year and from year to year.  However, constituent concentrations in the treated water may be modified as part of the treatment process.  Therefore, the treated water concentrations are accurate as tested on February 25,2008 (or date specified).   A distribution system sample site at the Central Fire Station in South Portland has also been included for your information.  Constituent concentrations in the treated water may change slightly with passage through the distribution system so water from your tap will be similar, but not necessarily identical to that at this South Portland site.

 

 

How is the water treated?

Greater Portland: Up to 52 million gallons per day (normally 23 MGD) can be pumped from Sebago Lake through the ozone contact tanks.  Each contact tank has five chambers where ozonated air can be bubbled up through the water.  It is the contact of ozone with the water that accomplishes disinfection.  The ozone concentration is measured in each chamber.   By the time the water reaches the end of the contact tanks, the primary disinfection is complete and the ozone has converted back to oxygen.  Chlorine and ammonia are then added to provide long lasting, continued disinfection in the water mains.  Other chemicals are also added at this point to help reduce corrosion.  They include sodium hydroxide for pH adjustment, and zinc orthophosphate for corrosion control.  Fluoride is added for dental health.

Steep Falls: This well system supplies the community with approximately 28,000 gallons of water each day.  Water is drawn from the wells by a vacuum system then pumped to a series of three tanks where the water is aerated for radon removal.  Chlorine is added to maintain a disinfectant residual in the system and sodium hydroxide is added for pH adjustment.  Fluoride is added for dental health.

 

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