7.3.7 Water Treatment | Chicago Public Schools

Softening

Typically, water softening is limited to applications where required for make-up water to a Steam Boiler Plant in order to limit pipe scaling and the need for additional water treatments. Water softening may be required if the service water to the site is considered “hard”. The service water is to be tested to determine the concentration of CaCO3. If the level is greater than 150 ppm (150 mg/L), the water will be considered hard. These non-steam related systems shall only be included after written approval by authorized CPS administrative personnel.

Water softening is a process that reduces or removes dissolved impurities that cause hardness in water. This is done by one of two methods: adding lime and soda ash to the raw water for very large volumes or passing the raw water through an ion-exchange process.

Water Quality Testing:

Conduct a “pre-design” water test using localized water sources as a proxy. When required, design appropriate treatment systems. Water delivered to the project for human consumption, handwashing and showers/baths meets the following thresholds:

Turbidity less than or equal to 1.0 NTU
Contains 9 CFU/100 mL total coliforms (including E. coli)
Lead less than 0.01 mg/L.
Arsenic less than 0.01 mg/L.
Antimony less than 0.006 mg/L.
Mercury less than 0.002 mg/L.
Nickel less than 0.07 mg/L.
Copper less than 1.0 mg/L.
Cadmium less than 0.005 mg/L.
Chromium (total) less than 0.1 mg/L.
Styrene less than 0.02 mg/L.
Benzene less than 0.005 mg/L.
Ethylbenzene less than 0.3 mg/L.
Vinyl chloride less than 0.002 mg/L.
Toluene less than 0.7 mg/L.
Xylenes (total: m, p and o) less than 0.5 mg/L.
Tetrachloroethylene less than 0.005 mg/L.
Total trihalomethanes (sum of dibromochloromethane, bromodichloromethane, chloroform and bromoform) less than 0.08 mg/L.
Total haloacetic acids (sum of chloroacetic, dichloracetic, trichloracetic, bromoacetic anddibromoacetic acids) less than 0.06 mg/L.
Atrazine less than 0.003 mg/L.
Simazine less than 0.002 mg/L.
2,4-Dichlorophenoxyacetic acid less than 0.07 mg/L.
Nitrate less than 50 mg/L (11 mg/L as nitrogen)
Fluoride less than 4 mg/L.
Total chlorine less than 4 mg/L.
Chloramine less than 4 mg/L.

Filtration

If, upon analysis of the service water to the site, water filtration is suggested by the EOR, the level of filtration and need shall be submitted for written approval by authorized CPS administrative personnel.