Section 179-19-009 - COMBINED FILTER EFFLUENT REQUIREMENTS009.01 All systems that use surface water or ground water under the direct influence of surface water and serve fewer than 10,000 persons, are required to filter, and utilize filtration other than slow sand filtration or diatomaceous earth filtration must meet the combined filter effluent turbidity requirements of 179 NAC 19-009.02 to 19-009.04. Systems that use slow sand or diatomaceous earth filtration are not required to meet the combined filter effluent turbidity limits of 179 NAC 19, but they must continue to meet the combined filter effluent turbidity limits in 179 NAC 13-006.009.02 Strengthened Combined Filter Effluent Turbidity Limits Systems must meet two strengthened combined filter effluent turbidity limits:
1. The first combined filter effluent turbidity limit is a "95th percentile" turbidity limit that systems must meet in at least 95% of the turbidity measurements taken each month. Measurements must continue to be taken as described in 179 NAC 13-007.01 and 13-007.03. Monthly reporting must be completed according to 179 NAC 19-011.01. The following table describes the required limits for specific filtration technologies. If Your System Consists of | Your 95th Percentile Turbidity Value Is |
1. Conventional Filtration or Direct Filtration | 0.3 NTU. |
2. All other "Alternative" Filtration | A value determined by the Director (not to exceed 1 NTU) based on the demonstration described in 179 NAC 19-009.03. |
2. The second combined filter effluent turbidity limit is a "maximum" turbidity limit which your system may at no time exceed during the month. Measurements must continue to be taken as described in 179 NAC 13-007.01 and 13-007.03. Monthly reporting must be completed according to 179 NAC 19-011.01. The following table describes the required limits for specific filtration technologies. If Your System Consists of | Your Maximum Turbidity Value Is |
1. Conventional Filtration or Direct Filtration | 1 NTU |
2. All other "Alternative" Filtration | A value determined by the Director (not to exceed 5 NTU) based on the demonstration as described in 179 NAC 19-009.03. |
009.03 Systems Using "Alternative Filtration" 19-009.03A Systems using alternative filtration (filtration other than slow sand filtration, diatomaceous earth filtration, conventional filtration, or direct filtration) are required to conduct a demonstration (see tables in 179 NAC 19-009.02). Systems must demonstrate to the Director, using pilot plant studies or other means, that their system's filtration, in combination with disinfection treatment, consistently achieves: 1. 99% removal of Cryptosporidium oocysts;2.99.9 % removal and/or inactivation of Giardia iambiia cysts; and
3.99.99 % removal and/or inactivation of viruses.
009.04 Systems using lime softening may acidify representative combined filter effluent turbidity samples prior to analysis using a protocol approved by the Director.179 Neb. Admin. Code, ch. 19, § 009