Section 327IAC8-2.6-20. Inactivation toolbox components; requirements for microbial toolbox components; enhanced treatment for Cryptosporidium

   (a) The following requirements are for calculation of CT values:

(1) CT is the product of C and T.

Where:	C	=	disinfectant concentration expressed in milligrams per liter
	T	=	disinfectant contact time expressed in minutes

(2) A PWS with treatment credit for chlorine dioxide or ozone under subsection (b) or (c) shall calculate CT at least once each day with both C and T measured during peak hourly flow as described under 327 IAC 8-2-8.7.

(3) A PWS with several disinfection segments in sequence, where a disinfection segment is defined as a treatment unit process with a measurable disinfectant residual level and a liquid volume:

(A) may calculate CT for each segment; and

(B) shall add the Cryptosporidium CT values in each segment to determine the CT for the treatment plant.

  (b) The following requirements are for calculation of CT values for chlorine dioxide and ozone:

(1) A PWS receives the Cryptosporidium treatment credit listed in the following table by meeting the corresponding chlorine dioxide CT value for the applicable water temperature, using the procedure described under subsection (a):

Table 20(a)
CT Values (mg⋅min/L) for Cryptosporidium Inactivation by Chlorine Dioxide1
Log Credit	Water Temperature, °C
	≤ 0.5	1	2	3	5	7	10	15	20	25	30
0.25	159	153	140	128	107	90	69	45	29	19	12
0.5	319	305	279	259	214	180	138	89	58	38	24
1.0	637	610	558	511	429	360	277	179	116	75	49
1.5	956	915	838	767	643	539	415	268	174	113	73
2.0	1275	1220	1117	1023	858	719	553	357	232	150	98
2.5	1594	1525	1396	1278	1072	899	691	447	829	188	122
3.0	1912	1830	1675	1537	1286	1079	830	536	347	226	147

¹A PWS may use this equation to determine log credit between the indicated values: Log credit = (0.001506 × (1.09116)^Temp) × CT.

(2) A PWS receives the Cryptosporidium treatment credit listed in the following table by meeting the corresponding ozone CT values for the applicable water temperature, using the procedure described under subsection (a):

Table 20(b)
CT Values (mg⋅min/L) for Cryptosporidium Inactivation by Ozone1
Log Credit	Water Temperature, °C
	≤ 0.5	1	2	3	5	7	10	15	20	25	30
0.25	6.0	5.8	5.2	4.8	4.0	3.3	2.5	1.6	1.0	0.6	0.39
0.5	12	12	10	9.5	7.9	6.5	4.9	3.1	2.0	1.2	0.78
1.0	24	23	21	19	16	13	9.9	6.2	3.9	2.5	1.6
1.5	36	35	31	29	24	20	15	9.3	5.9	3.7	2.4
2.0	48	46	48	38	32	26	20	12	7.8	4.9	3.1
2.5	60	58	52	48	40	33	25	16	9.8	6.2	3.9
3.0	72	69	63	57	47	39	30	19	12	7.4	4.7

¹A PWS may use this equation to determine log credit between the indicated values: Log credit = (0.0397 × (1.09757)^Temp) × CT).

  (c) The commissioner may approve alternative chlorine dioxide or ozone CT values to those listed in subsection (b):

(1) on a site-specific basis; and

(2) based on a site-specific study conducted by the PWS that follows a protocol approved by the commissioner.

  (d) A PWS may receive Cryptosporidium, Giardia lamblia, and virus treatment credits for ultraviolet (UV) light reactors by meeting the following:

(1) The ultraviolet (UV) light reactors must achieve the corresponding UV dose values shown under subdivision (3).

(2) A PWS shall validate and monitor UV reactors as described under subdivisions (4) and (5) to demonstrate that they are achieving a particular UV dose value for treatment credit.

(3) The UV light treatment credits listed under Table 20(c) in clause (C) are available under the following conditions:

(A) For UV light at a wavelength of two hundred fifty-four (254) nanometers as produced by a low pressure mercury vapor lamp.

(B) To receive treatment credit for lamp types other than two hundred fifty-four (254) nanometers, a PWS shall demonstrate an equivalent germicidal dose through reactor validation testing described under subdivision (4).

(C) The UV dose values under the following table are applicable only to post-filter applications of UV in filtered systems:

Table 20(c)
UV Dose Table for Cryptosporidium, Giardia Lamblia, and Virus Inactivation Credit
Log Credit	Cryptosporidium UV dose (mJ/cm2)	Giardia lamblia UV dose (mJ/cm2)	Virus UV dose (mJ/cm2)
0.5	1.6	1.5	39
1.0	2.5	2.1	58
1.5	3.9	3.0	79
2.0	5.8	5.2	100
2.5	8.5	7.7	121
3.0	12	11	143
3.5	15	15	163
4.0	22	22	186

(4) PWSs shall use UV reactors that have undergone validation testing to determine the operating conditions under which the reactor delivers the UV dose required under subdivision (3), for example, validated operating conditions. These operating conditions must include flow rate, UV intensity as measured by a UV sensor, and UV lamp status and meet the following:

(A) When determining validated operating conditions, a PWS shall account for the following factors:

(i) UV absorbance of the water.

(ii) Lamp fouling and aging.

(iii) Measurement uncertainty of online sensors.

(iv) UV dose distributions arising from the velocity profiles through the reactor.

(v) Failure of UV lamps or other critical system components.

(vi) Inlet and outlet piping or channel configurations of the UV reactor.

(B) Validation testing must include the following:

(i) Full scale testing of a reactor that conforms uniformly to the UV reactors used by the PWS.

(ii) Inactivation of a test microorganism whose dose response characteristics have been quantified with a low pressure mercury vapor lamp.

(5) Reactor monitoring requirements are as follows:

(A) A PWS shall monitor its UV reactors to determine if the reactors are operating within validated conditions, as determined under subdivision (4).

(B) UV reactor monitoring must include the following:

(i) UV intensity as measured by a UV sensor that must undergo:

(AA) verification of calibration; and

(BB) recalibration;

in accordance with a protocol approved by the commissioner.

(ii) Flow rate.

(iii) Lamp status.

(iv) Other parameters the commissioner designates based on UV reactor operations.

(6) To receive treatment credit for UV light, a PWS shall treat at least ninety-five percent (95%) of the water delivered to the public each month by UV reactors operating within validated conditions for the required UV dose, as described under subdivisions (3) and (4). A PWS shall demonstrate compliance with this condition through the monitoring required under subdivision (5)(A).

(Water Pollution Control Division; 327 IAC 8-2.6-20; filed May 7, 2010, 9:30 a.m.: 20100602-IR-327080198FRA)