Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 317 - DESIGN CRITERIA PRIOR TO 2008 › Section 317.4 - Wastewater Treatment Facilities

Current through Reg. 49, No. 28; July 12, 2024
(a)
				General requirements. Whenever possible, existing data of flows and raw waste
				strength from the same plant or nearby plants with similar service areas should
				be used in design of treatment facilities. When using such data for design
				purposes, the variability of data should be considered and the design based on
				the highest flows and strengths encountered during normal operating periods
				taking into consideration possible infiltration/inflow. In the absence of
				existing data, the following are generally acceptable parameters to which must
				be added appropriate allowances for inflow and infiltration into the collection
				system to obtain plant influent characteristics.
Attached
				  Graphic
(1) Effluent
				quality. Wastewater treatment plants shall be designed to consistently meet the
				effluent concentration and loading requirements of the applicable waste
				disposal permit.
(2) Effluent
				quantity. The design flow of a treatment plant is defined as the wet weather,
				maximum 30-day average flow. The design basis shall include industrial
				wastewaters which will enter the sewerage system. The engineering report shall
				state the flow and strength of wastewaters from industries which individually
				contribute 5.0% or more of plant flow or loading and discuss the aspect of
				hazardous or toxic wastes. It is the intent of these design criteria that the
				permit conditions not be violated. The engineering report shall list the design
				influent flow and concentration of five-day biochemical oxygen demand
				(BOD5), total suspended solids (TSS), or other
				parameters for the following:
(A) dry weather
				30-day average (QDW);
(B) wet weather maximum 30-day average
				(QDW); and
(C) two-hour peak flow
				(QpW).
(3) Piping. The piping within all plants
				shall be arranged so that when one unit is out of service for repairs, plant
				operation will continue and emergency treatment can be accomplished. Valves and
				piping shall be provided and sized to allow dewatering of any unit, in order
				that repairs of the unit can be completed in as short a period of time as
				possible. Portable pumping units may be used for dewatering small treatment
				plants (design flow of less than 100,000 gallons per day) or interim
				facilities. Removed wastes must be stored for retreatment or delivered to
				another treatment facility for processing. Consideration shall be given in
				design for means to clean piping, especially piping carrying raw wastewater,
				sludges, scum, and grit.
(4) Peak
				flow. For treatment unit design purposes, peak flow is defined as the highest
				two-hour average flow rate expected to be delivered to the treatment units
				under any operational condition, including periods of high rainfall (generally
				the two-year, 24-hour storm is assumed) and prolonged periods of wet weather.
				With pumped inflow, clarifiers shall have the capacity of all pumps operating
				at maximum wet well level unless a control system is provided that will limit
				the pumping rate to the firm capacity. This flow rate may also include skimmer
				flow, thickener overflow, filter backwash, etc. All treatment plants must be
				designed to hydraulically accommodate peak flows without adversely affecting
				the treatment processes. The engineer shall determine, by methods acceptable to
				the commission, the appropriate peak flow rate, including the possibility of
				utilizing standby pumps. The proposed two-hour peak flow rate, together with a
				discussion of rationale, calculations, and all supporting flow rate data shall
				be, unless presented in the preliminary engineering report, included in the
				final engineering design report. Special storm flow holding basins or flow
				equalization facilities can be specified to partially satisfy the requirements
				of this section where all treatment units within a plant are not sized for peak
				flow. See § 317.9 of this title (relating to Appendix A) for referencing a
				two-year 24-hour rainfall event.
(5) Auxiliary power. The need for auxiliary
				power facilities shall be evaluated for each plant and discussed in the
				preliminary and final engineering reports. Auxiliary power facilities are
				required for all plants, unless dual power supply arrangements can be made or
				unless it can be demonstrated that the plant is located in an area where
				electric power reliability is such that power failure for a period to cause
				deterioration of effluent quality is unlikely. Acceptable alternatives to
				auxiliary power include the ability to store influent flow or partially treated
				wastewater during power outage. Auxiliary power may be required by the
				commission for plants discharging near drinking water reservoirs, shellfish
				waters, or areas used for contact recreation, and for plants discharging into
				waters that could be unacceptably damaged by untreated or partially treated
				effluent. For more information on power reliability determination and emergency
				power alternatives, refer to § 317.3(e) of this title (relating to Lift
				Stations).
(6) Component
				reliability. Multiple units may be required based upon the uses of the
				receiving waters and the significance of the treatment units to the treatment
				processes.
(7) Stairways, walkways,
				and guard rails. Basins having vertical walls terminating four or more feet
				above or below ground level shall provide a stairway to the walkway. Guard
				rails on walkways shall have adequate clearance space for maintenance
				operations (see § 317.7 of this title (relating to Safety)).
(8) Public drinking water supply connections.
				There shall be no water connection from any public drinking water supply system
				to a wastewater treatment plant facility unless made through an air gap or a
				backflow prevention device, in accordance with American Water Works Association
				(AWWA) Standard C506 (latest revision) and AWWA Manual M14. All backflow
				prevention devices shall be tested annually with their test and maintenance
				report forms retained for a minimum of three years. All washdown hoses using
				potable water must be equipped with atmospheric vacuum breakers located above
				the overflow level of the washdown area.
(9) Ground movement protection. The
				structural design of treatment plants shall be sufficient to accommodate
				anticipated ground movement including any active geologic faults and allow for
				independent dewatering of all treatment units. Plants should not be located
				within 50 feet of geologic faults.
(10) Odor control facilities. The need for
				odor control facilities shall be evaluated for each plant. Factors to be
				considered are the dissolved oxygen level of the incoming sewage and the type
				of treatment process proposed.