Laboratory Analysis
System Administration
Potpourri
MCLs and MCLGs
Backflow Prevention

100

This chemical turns pink in the presence of free and/or combined chlorine residual.
What is DPD (N, N-diethyl-p-phenylenediamine)

100

Records of sanitary surveys must be maintained for at least this long.
What is 10 years.

100

This is the technical term for a sticky mat of fine sand and suspended matter that forms on the surface of a sand filter
What is schmutzdeke.

100

The MCL for combined radium in pCi/L
What is 5

100

This type of backflow preventer is often used at a mop sink or yard hydrant. They may be quick disconnect.
What is a Hose Connection Vacuum Breaker

200

Alkalinity consists primarily of this constituent at pH values typical in drinking water systems.
What is carbonate.

200

Records of turbidity sample results must be maintained for at least this long.
What is 5 years

200

The primary difference between conventional and direct filtration water treatment plants.
What is direct filtration plants do not have a sedimentation basin.

200

The action limit for Lead
What is 15 ug/L

200

This backflow preventer contains two shut-off valves and two check assemblies that are independently operated.
What is a Reduced Pressure Assembly

300

This technical term refers to the appearance of a sample before it is filtered. Brown or red are two examples.
What is apparent color.

300

Most groundwater systems treating less than 2 MGD require a certified operator at this level unless chemical treatment or advanced treatment technology is in use.
What is level D

300

This is the minimum recommended water pressure in a distribution system even during fire flows.
What is 20 psi.

300

The secondary MCL for chloride
What is 250 mg/L

300

For an Air Gap type backflow preventer to be effective, the air gap should be at least this big.
What is 2 times the pipe diameter

400

In a presence/absence test, the samples are incubated at this temperature for at least 24 hours.
What is 35 degrees Centigrade

400

The test results for a finished water sample show a pH of 8.0 and a pH(sat) of 7.5 The Langelier Index will be ________.
What is positive or greater than zero.

400

This type of backflow preventer is required for some high risk connections and cannot be installed in a crawl space or other inaccessible area.
What is Reduced Pressure Assembly

400

The secondary MCL for Total Dissolved Solids or TDS
What is 500 mg/L

400

Backflow preventers should be tested, where possible, at least this often.
What is Annually by a certified backflow preventer inspector.

500

The charge cloud around a particle in a water sample that determines how particles interact with one another is referred to as this.
What is Zeta Potential

500

Your department uses 80 units of an item per week. You are required to maintain a 10-week reserve of this item at all times and it requires 4 weeks to obtain a new supply. The minimum reorder point is this.
What is 1,120 units.

500

pH values can't be averaged by adding the values together and dividing by the number of measurements for this reason.
What is pH is a log value. You must first take the inverse log of each measurement. Then, add the inverse logs together and divide by the total number of measurements. Finally, take the log of the average.

500

The MCLG for Acrylamide
What is 0 mg/L

500

This type of backflow preventer can prevent damage to home water heaters from water hammer and/or sudden pressure losses in the distribution system.
What is none.