Ala. Admin. Code r. 335-7-6-.06

Current through Register Vol. 43, No. 1, October 31, 2024

Section 335-7-6-.06 - Conventional Treatment Processes

All surface water and ground water under the influence of surface water treatment plants utilizing a conventional treatment process must meet the following requirements:

(a) Existing facilities (facilities constructed or permitted for construction prior to January 1, 2006) may obtain a waiver from these regulations for any portion that they currently do not comply with. Existing facilities modified after this date must include provisions to address these regulations.

(b) Mixing Basins: Provision shall be made for the rapid disbursement of coagulants in the raw water and the development of a floc according to the following:

1. A minimum of two mixing units shall be provided when mechanical mixers are used. Hydraulic mixing is permitted with prior approval from the Department.

2. Provision shall be made for the application of chemicals at various points in the treatment train.

3. A minimum detention time of 30 minutes shall be provided under normal flow conditions in the flocculation basin. The plant must demonstrate a minimum of sixty percent detention time before requesting authorization to place the water treatment plant into service.

4. A minimum of two multi-stage flocculation units is required.

5. Each flocculation unit shall be equipped with variable speed drive unless hydraulic flocculation is utilized.

(c) Settling Basins: Provision shall be made for the settling of floc according to the following:

1. A minimum of two sedimentation basins is required. A minimum settling period of four hours shall be provided in the basins. The plant must demonstrate a minimum of sixty percent settling time before requesting authorization to place the water treatment plant into service. Existing plants having only one sedimentation basin may obtain a waiver from the Department for the requirement for two sedimentation basins if the Department determines that construction of the additional basin would have a negative impact on plant and system operation.

2. Each basin shall be equipped with an automatic sludge removal system and drains.

3. Each basin shall be designed with a minimum length to width ratio of 2:1 and shall have a maximum surface overflow rate of 850 gallons per day per square foot of basin area.

4. Inlet and outlet design shall prevent short-circuiting and destruction of floc particles.

(d) Conventional Filtration: Provision shall be made for the filtering of settled water according to the following:

1. A minimum of two gravity type rapid dual media filters are required.

2. The rate of filtration shall not exceed two gallons per minute per square foot of filter bed area unless otherwise approved by the Department.

3. Each filter must be equipped with filter-to-waste capability.

4. Sufficient head room shall be available above filters to allow inspection of the facility and access to the filter and sufficient illumination shall be provided above all filters that are enclosed.

5. Sample taps shall be provided on the filter effluent line from each filter.

6. Media used shall meet departmental design requirements.

7. A method of constantly controlling the rate of flow through each filter shall be provided.

8. A filter flow indicator and head loss indicator shall be present at each filter.

9. Provisions shall be made for continuously monitoring and recording the turbidity of the effluent from each filter and the filter-to-waste.

10. Equipment shall be installed and maintained to allow proper cleaning and backwashing of filters. Filters shall be backwashed when the head loss approaches or exceeds six feet, effluent turbidity approaches or exceeds 0.3 NTU, or there is a rapid increase in effluent turbidity. Water used for all backwashing procedures shall meet primary and secondary drinking water standards. A flow control device shall be available to regulate and indicate the rate of backwashing. Filters shall be designed to allow the operator to observe the backwashing procedures. After backwashing, the filter shall be filtered to waste until the turbidity in the filter to waste water is approximately 0.1 NTU, but no greater than 0.3 NTU.

Author: Edgar K. Hughes

Ala. Admin. Code r. 335-7-6-.06

New Rule: Filed December 21, 1998; effective January 25, 1999. Amended: Filed May 2, 2000; effective June 6, 2000. Repealed and New Rule: Filed November 7, 2005; effective December 12, 2005.

Statutory Authority:Code of Ala. 1975, §§ 22-23-33, 22-23-49, 22-22A-5, 22-22A-6.