Calculate the Langelier Index from the results of water testing shown below:
Initial pH = 7.9
pH after saturation = 8.3

-0.4

In the corrosion cell, or a piece of iron pipe, this is the positive pole, or electrode

The anode

The absence of dissolved oxygen and low pH make ideal conditions for what?

The growth of anaerobic bacteria

By rule, samples for lead and copper must be 'first-draw' samples. What defines a 'first-draw' sample?

A sample that is the first liter of water collected from a tap that has not been used for at least 6 hours

From the list of lead sample results shown, calculate the 90th percentile lead
result.
0.003 mg/L
0.004 mg/L
0.020 mg/L
0.023 mg/L
0.045 mg/L
0.076 mg/L
0.003 mg/L
0.090 mg/L
0.002 mg/L
0.002 mg/L

0.076 mg/L

The results of the Marble Test are as follows:

•Initial water pH = 7.8

Finished water pH = 7.5

•Initial water hardness = 156 mg/L as CaCO3

Finished water hardness = 143 mg/L as CaCO3

•Initial water alkalinity = 198 mg/L as CaCO3

Finished water alkalinity = 172 mg/L as CaCO3

What do these test results indicate?

The initial water is saturated

In a piece of iron pipe that is experiencing tuberculation, a pit in the pipe wall and subsequent tubercule forms at which location?

At the anode

What analysis uses a pinch of powdered calcium carbonate along with results of hardness, alkalinity and pH tests?

Marble test

If the result of the Langelier Index test of water in a distribution system is positive, which of the following statements is correct?

The water in the distribution system is scale forming

According to the lead and copper rule, samples must be collected at locations the utility has identified as high risk. These locations include homes with lead pipes, lead service lines and what other factor?

Homes with lead solder installed after 1982

Water that contains dissolved salts is known as what?

Electrolyte

This element is considered the most corrosive component of water chemistry

Oxygen

Phosphate based corrosion inhibitors may cause what condition?

Encourage growth of biofilms on pipe walls

The plant operator is receiving complaints from customers in a section of the service area about red colored water, metallic taste and low water pressure. The area is also prone to water leaks and water main breaks. What is happening in the water system?

Corrosion of the metal water mains is occurring