3745-81-74 Turbidity and disinfection monitoring requirements for surface water systems.

 

 

 

3745-81-74                  Turbidity      and    disinfection      monitoring    requirements       for surface water systems.

 

 

A public water system that uses a surface water source, in whole or in part, as defined in rule 3745-81-01 of the Administrative Code shall monitor conduct turbidity and disinfection monitoring in accordance with this rule.

 

(A)   Turbidity measurements as required byto ensure compliance with rule 3745-81-73 of the Administrative Code shall be performed on representative samples of filtered water at least every four hours that the water treatment plant is in operation. If using grab sampling for turbidity monitoring, samples shall be obtained within the first and last hours of filter operation and at least every four hours in between. A public water system may substitute continuous turbidity monitoring for grab sample monitoring if the public water system validates the continuous measurement for accuracy on a regular basis using a protocol approved by acceptable to the director. Turbidity monitoring of filtered water may be:

 

(1)  At the combined filter effluent prior to entry into the clearwell,; or

 

(2)    The time weighted average of turbidity measurements from each individual filter effluent, if each filter has essentially the same loading rate; or

 

(3)   At the clearwell effluent,; or

 

(4)   At the plant effluent or immediately prior to entry into the distribution system.

 

(B)    For public Public water system(s) using conventional filtration treatment or direct filtration treatment and providing water to a combined population of at least ten

thousand,  shall  also  conduct  individual  filter  turbidity performed as follows:

monitoring  shall  be

(1)   A public water system that provides conventional filtration treatment or direct filtration treatment shall conduct continuous monitoring of turbidity for each individual filter effluent. The public water system shall validate the continuous measurement for accuracy on a regular basis using the protocol approved by acceptable to the director. The public water system shall record the results of individual filter monitoring every fifteen minutes. A public water system serving a combined population of less than ten thousand and which has two filters may conduct continuous monitoring of turbidity of the combined filter effluent, prior to entry into the clearwell, in lieu of individual filter effluent turbidity monitoring. The public water system shall record the results of the combined filter monitoring every fifteen minutes.

(2)   If there is a failure in the continuous turbidity monitoring equipment, the public

water system shall conduct grab sampling every four hours in lieu of continuous monitoring until the continuous turbidity monitoring equipment is repaired and placed back online. A public water system serving a combined population of at least ten thousand has no more than five working days after the failure of the equipment to repair the continuous turbidity monitoring equipment and to place it back online. A public water system serving a combined population of less than ten thousand has no more than fourteen days after the failure of the equipment to repair the continuous turbidity monitoring equipment and to place it back online.

(C) Turbidity  analysis  shall  be  conducted  as  specified  in  paragraph  (C)  of  rule 3745-81-27 of the Administrative Code.

(C)(D) The residual disinfectant concentration of the water entering the distribution system shall be monitored continuously, and the lowest value must be recorded each day, except that:

(1)    If there is a failure in the continuous disinfection monitoring equipment, the public water system shall conduct grab sampling every four hours in lieu of continuous monitoring until the continuous monitoring equipment is repaired and place back online. A public water system has no more than five working days after failure of the equipment to repair the continuous monitoring equipment and place it back online; and

(2)    Public water systems serving three thousand three hundred or fewer persons may, with prior approval acceptance by the director, take grab samples in lieu of providing continuous monitoring. Grab sample monitoring shall require at least one sample every four hours that the water treatment plant is in operation.

(D)(E) The residual disinfectant concentration shall be measured at least at the same points in the distribution system and at the same time as total coliforms are sampled, as specified in rule 3745-81-21 of the Administrative Code.

(E)(F) Parameters necessary to determine the sufficiency of disinfection prior to the first customer as required in rule 3745-81-72 of the Administrative Code shall be measured and recorded at the peak hourly flow rate each day the public water system is in operation. Public water systems which do not record any or all of the parameters set forth in paragraphs (E)(1)(F)(1) to (E)(3)(F)(3) of this rule on continuously recording devices, may estimate the period at which peak hourly flow will occur from records of flow rates from previous days for that water plant. The parameters necessary to calculate the actual CT value may then be those measured during this estimated peak hourly flow period. Temperature, pH, and residual disinfection  concentration  shall  be  analyzed  in  accordance  with  the  methods

specified in rule 3745-81-27 of the Administrative Code. These The parameters necessary to calculate the actual CT value include:

(1)      The temperature of the disinfected water at each residual disinfectant concentration sampling point. The director may accept an alternative representative sampling point.

(2)     The pH of the disinfected water at each residual disinfectant concentration sampling point.

(3)   The kind of disinfectant used and the residual disinfectant concentration at each sampling point before or at the first customer.

(4)     The flow rate, clearwell used volume or depth, approved effective volume factor, aandand any other parameters needed to calculate the disinfectant contact time for each sampling point during each day's peak hourly flow.

(5)     The actual value of CT value as determined for each day in the month, calculated from the above water temperature, pH, residual disinfectant concentration, disinfectant contact time(s), and other characteristics of the water treatment plant as it was operating at peak hourly flow rate for that day.

(6)      The required minimum value for CT value for each day of the month, determined from the water temperature, the water pH, the disinfectant in use, and other information referred to in rule 3745-81-72 of the Administrative Code.

(7)    The number of days, if any, for which the required minimum CT value was greater than the determined actual value of CT value.

Effective:                                01/01/2005

R.C. 119.032 review dates:    05/05/2004 and 01/01/2010

CERTIFIED ELECTRONICALLY

Certification

07/23/2004

Date

Promulgated Under:   119.03

Statutory Authority:   RC Section 6109.04 Rule Amplifies:                                    RC Section 6109.03 and

6109.04

Prior Effective Dates: 12/31/90, 1/1/02