455Total coliform, fecal coliform, and E. coli are all indicators of drinking water quality. The
total coliform group is a large collection of different kinds of bacteria. Fecal coliforms are
types of total coliform that mostly exist in feces. E. coli is a sub-group of fecal coliform.
When a water sample is sent to a lab, it is tested for total coliform. If total coliform is
present, the sample will also be tested for either fecal coliform or E. coli, depending on the
lab testing method.
- What problems are associated with Hydrogen Sulfide in the water?
Hydrogen sulfide is a gas which, when dissolved in water, gives it a “rotten egg” odor.
Chlorination will remove this gas from the water but the effectiveness of the chlorine for
disinfection is lessened. - When Hydrogen sulfide reacts with chlorine, it produces Sulfuric acid and
elemental Sulfur: It is therefore recommended that aeration be applied prior to the
addition of chlorine for the most effective disinfection. - Why is it important to know what the turbidity of the water is when using
chlorine?
To be careful not to overdose with chlorine or properly dose with chlorine. - What is the log removal for Cryptosporidium?
The LT1ESWTR extends further this necessary protection from Cryptosporidium to
communities of fewer than 10,000 persons. Today's rule for the first time establishes
Cryptosporidium control requirements for systems serving less than 10,000 persons by
requiring a minimum 2-log removal for Cryptosporidium. The rule also strengthens filter
performance requirements to ensure 2-log Cryptosporidium removal, establishes
individual filter monitoring to minimize poor performance in individual units, includes
Cryptosporidium in the definition of GWUDI, and explicitly considers unfiltered system
watershed control provisions. The rule also reflects a commitment to the importance of
maintaining existing levels of microbial protection in public water systems as plants take
steps to comply with newly applicable DBP standards. - What is the log removal?
This log-reduction terminology was developed by engineers as a way to express levels of
decreased biological contamination in water by factors of 10 that could be easily converted
to percent reduction. The most commonly used logarithmic base is 10 because it is
compatible with our base-10 decimal system.