reglab/statecodes huggingface dataset:
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 4 - Preliminary Processes › Section 9VAC25-790-500 - Screening

Current through Register Vol. 40, No. 24, July 15, 2024
A. Conventional
					 preliminary treatment shall include adequate screening to remove solids and
					 debris that could interfere with the performance of downstream unit operations.
					 The process design shall address the means of proper waste management for
					 screenings.
B. Requirements.
					 Protection for pumps and other equipment shall be provided by installing large
					 openings, one inch or more, coarse screens, or bar racks, and smaller openings
					 screens. All screen equipment and facilities shall be readily accessible for
					 maintenance. Small openings, fine screening, or comminution should follow grit
					 removal, which should be preceded by coarse screening. Screen locations are to
					 be provided as follows:
1. Manually cleaned
					 screens shall be provided at all sewage treatment works unless adequate
					 redundant mechanical screens are provided and manually cleaned screens shall be
					 located in open areas with easy access. Mechanical screens that can be manually
					 cleaned upon mechanical failure may be used to meet this requirement.
2. Manually cleaned screens located in deep
					 pits shall be provided with stairway access, adequate lighting and ventilation,
					 and convenient and adequate means for removing screenings.
3. Screening devices installed in a building
					 where other equipment or offices are located shall be separated from the rest
					 of the building, provided with separate outside entrances, and provided with
					 adequate means of ventilation.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 4 - Preliminary Processes › Section 9VAC25-790-510 - Grit removal facilities

Current through Register Vol. 40, No. 24, July 15, 2024
A.
					 Grit removal unit operations facilities shall be provided for all sewage
					 treatment works with a design capacity of 0.15 million gallons per day or
					 greater and are required for treatment works receiving sewage from combined
					 sewers or from sewer systems receiving substantial amounts of grit. Grit
					 removal facilities should be provided at all sewage treatment works.
1. Grit removal facilities should be located
					 ahead of pumps and comminuting devices. Coarse bar racks and other suitable
					 screens should be placed ahead of mechanically cleaned grit removal
					 facilities.
2. Treatment works
					 treating wastes from combined sewers shall have at least two mechanically
					 cleaned grit removal units, with provisions for unit bypassing.
3. A single manually cleaned or mechanically
					 cleaned grit removal unit, with a unit bypass, is acceptable for those sewage
					 treatment works with a design capacity of less than 0.15 million gallons per
					 day and serving separate sanitary sewer systems.
4. Minimum facilities for larger treatment
					 works serving separate sanitary sewers shall be at least one mechanically
					 cleaned unit with a unit bypass.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 4 - Preliminary Processes › Section 9VAC25-790-520 - Pre-aeration

Current through Register Vol. 40, No. 24, July 15, 2024
Aeration of pretreated sewage should be provided whenever
						the low dissolved oxygen, or anaerobic condition, of the sewage can interfere
						with downstream unit operation reliability. Pre-aeration may be used to prevent
						solids deposition problems in on-line or off-line equalization or storage
						basins.
1. Pre-aeration unit
					 operations shall be designed so that removal from service will not interfere
					 with normal downstream operation of the remainder of the treatment
					 process.
2. Inlet and outlet
					 devices shall be designed to ensure proper distribution and help prevent solids
					 deposition, while minimizing any hydraulic short circuiting effects.
3. The aeration equipment shall be capable of
					 obtaining both adequate mixing and self-cleaning velocities within the basin.
					 Any of the types of equipment used for aeration of biological reactors may be
					 utilized.
4. A satisfactory means
					 of grit removal shall be provided for operation of pre-aeration
					 basins.
Statutory Authority
§ 62.1-44.19 of the Code of Virginia.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-540 - Sludge stabilization

Current through Register Vol. 40, No. 24, July 15, 2024
The selection and operation of the sludge treatment or
						stabilization process shall be based on the ultimate utilization of the final
						sludge product. Land based management of treated sewage sludge may require the
						production of biosolids as described in the Virginia Pollution Abatement Permit
						Regulation (9VAC25-32) or Virginia Pollutant Discharge Elimination System
						Permit Regulation (9VAC25-31). The design requirements for the treatment and
						stabilization processes described in this chapter are based on the assumption
						that they must accomplish the necessary processing of sewage sludge at the
						treatment works. Consideration will be given to reducing design requirements,
						on a case-by-case basis, for treatment works employing series operation of two
						or more stabilization processes or methods in accordance with the means of
						sludge management. The standard buffer distance of 200 feet shall be provided
						between the walls of open and exposed sludge treatment operations and the
						boundaries of the site area in which either controlled use or access
						restrictions apply.
Statutory Authority
§ 62.1-44.15 of the Code of Virginia.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-560 - Aerobic sludge digestion

Current through Register Vol. 40, No. 24, July 15, 2024
A.
					 Aerobic sludge digestion reactors shall be designed for effective mixing and
					 aeration. If diffusers are used, they shall be of the type that minimizes
					 clogging and they should be designed to permit removal for inspection,
					 maintenance and replacement without dewatering the tanks.
B. Design. Multiple aerobic digesters are
					 required at all treatment works having a design flow capacity of more than 0.5
					 mgd. The size and number of aerobic sludge digesters shall be determined by
					 rational calculations based upon such factors as (i) volume of sludge added;
					 (ii) type and percent solids; (iii) the required volatile solids reduction for
					 stabilization; (iv) allowance for sludge and supernatant storage; and (v) the
					 minimum design temperature of the digester contents.
1. Calculations shall be submitted to justify
					 the design and shall include design digester temperature based on the type of
					 mixing equipment and other factors.
2. Digester volume shall be a minimum of 20%
					 of the average design flow of the treatment works. The design digester volume
					 should be increased up to 25% of the average design flow if the wastewater
					 temperature will remain below 10°C (50°F) for an extensive period of
					 time (60 days/year).
3. A reduction
					 in requirements for hydraulic detention time may be given for treatment works
					 designed to be operated in the extended aeration mode, or coupled with
					 additional stabilization processes, or operated at elevated
					 temperatures.
4. Facilities shall
					 be provided for effective separation and withdrawal, or decanting of
					 supernatant.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-570 - Composting

Current through Register Vol. 40, No. 24, July 15, 2024
A. Conventional
					 sludge composting facilities aerobically process digested, or otherwise
					 treated, sewage sludge that is uniformly mixed with other organic materials and
					 bulking agents to facilitate biological decomposition of organics. The treated
					 sewage sludge will be exposed to temperatures at or above 55°C for three
					 consecutive days or more. The method of mixing and aeration, and the carbon to
					 nitrogen characteristics, of the compost mix are critical to the process
					 design.
B. General design. Unless
					 the facility is totally enclosed, an appropriate buffer shall be established on
					 a case-by-case basis by considering both the locations of any residential area,
					 hospitals, nursing homes for the elderly and serum production centers and the
					 prevailing wind at such locations. Local jurisdictions impacted by this
					 restriction shall be so notified.
1. All
					 compost facilities shall be provided with adequate means to prevent and control
					 odors as necessary.
2. All compost
					 facilities shall be provided with all-weather roads to and from the facility,
					 as well as between the various process operations.
3. The receiving, mixing, composting, curing,
					 drying, screening, and storage areas shall be paved with asphaltic concrete,
					 reinforced concrete, or other impervious, structurally stable material that
					 provides similar site characteristics.
4. The facility shall be graded to prevent
					 uncontrolled runoff and a suitable drainage system shall be provided to collect
					 all process wastewater and direct it to storage and treatment facilities.
					 Process wastewater includes water collected from paved process areas. The
					 capacity of the drainage system, including associated storage or treatment
					 works system shall be based on the 24-hour rainfall of a 10-year return
					 frequency.
5. All facility process
					 wastewater and sanitary wastewater shall be collected and treated prior to
					 discharge.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-580 - Heat treatment

Current through Register Vol. 40, No. 24, July 15, 2024
A. The
					 design of heat treatment systems shall be based on the anticipated sludge flow
					 rate (gpm) with the required heat input dependent on sludge characteristics and
					 concentration. The system should be designed for continuous 24-hour operation
					 to minimize additional heat input to start up the system. Measures for the
					 adequate control of odors shall be stipulated for review.
B. Design. Multiple units shall be provided
					 unless nuisance-free storage or alternate stabilization methods are available,
					 to avoid disruption to treatment works operation when units are not in service.
					 If a single system is provided, standby grinders, fuel pumps, air compressor
					 (if applicable), and dual sludge pumps shall be required.
1. A reasonable downtime for maintenance and
					 repair based on data from comparable facilities shall be included in the
					 design. Adequate storage for process feed and downtime shall be included.
					 Control parameters shall be adequately monitored. Continuous recorders to
					 monitor temperatures shall be provided.
2. Due to the large variation in incineration
					 processes, equipment types, and configurations characteristic of currently
					 available incineration systems, it is not feasible to stipulate specific design
					 criteria. Therefore, these systems shall be considered on a case-by-case basis.
					 Design of these systems should be based on pilot plant studies or data from
					 comparable facilities.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-590 - Chemical treatment

Current through Register Vol. 40, No. 24, July 15, 2024
A. The
					 fundamental design areas to be considered include chemical feeding, mixing, and
					 storage capacity. Chemical treatment operation controls may include pH, contact
					 time and mixture temperature.
B.
					 Alkaline treatment. The three design parameters typically considered
					 fundamental for design of an alkaline stabilization system include pH, contact
					 time, and mixture temperature. The alkaline additive dosage required to
					 stabilize sludge is determined by the type of sludge, its chemical composition
					 and the solids concentration. Performance data taken from pilot plant test
					 programs or from comparable facilities should be used in determining the proper
					 dosage.
1. For conventional treatment, the
					 design objective shall be to furnish uniform mixing in order to maintain a pH
					 of 12 or above for two hours or more in the alkaline additive-sludge mixture.
					 The design criteria for accomplishing adequate treatment may include:
a. Adding a controlled dosage of alkaline
					 agents to sludge and providing uniform mixing of the sludge and
					 agents.
b. Bringing the alkaline
					 additive-sludge mixture pH to the design objective, such as a mixture pH of
					 12.5 or more and maintaining the mixture pH above 12.5 for 30 minutes or
					 more.
c. Providing capacity to
					 achieve a temperature of the alkaline-sludge mixture of more than 52°C, if
					 desired, and maintaining a sufficient temperature over a measured contact
					 period to ensure pasteurization.
d.
					 Maintaining conditions so that the sludge is not altered or further distributed
					 for two hours or more after alkaline treatment.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-600 - Sludge thickening

Current through Register Vol. 40, No. 24, July 15, 2024
A. Sludge
					 thickening to decrease the liquid fraction should be considered for volume
					 reduction and conditioning of sludges prior to treatment and management.
					 Biological sludges returned to reactors should be thickened to provide for
					 effective control of biomass. Prior to conventional treatment of biosolids,
					 thickening should be provided to reduce volume and to condition the raw sludge
					 flow.
B. General design. Thickener
					 design shall provide adequate capacity to meet peak demands. Thickeners should
					 be designed to prevent septicity during the thickening process.
1. A sludge handling bypass around the
					 thickening process is required. Dual units or alternate storage is required for
					 all treatment works of greater than 1 mgd capacity.
2. Thickeners shall be provided with a means
					 of continuous return of supernatant for treatment. Provisions for side-stream
					 treatment of supernatant should be considered.
3. Consideration should be given to any
					 potential treatment advantages obtained from the blending of sludges from
					 various treatment processes.
4.
					 Odor control shall be addressed with consideration being given to flexibility
					 of operations and changes of influent sludge characteristics.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-620 - Sludge drying beds

Current through Register Vol. 40, No. 24, July 15, 2024
A. Actual
					 performance data from similar facilities should be provided for bed sizing. If
					 such data is unavailable, the following general guidelines shall been used as
					 the minimum:
Stabilization Process
Loading Rate*
i. Anaerobic Digestion
20.0
ii. Aerobic Digestion and
15.0
iii. Other Stabilization Processes
15.0
*lbs dry solids/sq ft/year
B. Design. Area requirements for covered beds
					 or greenhouse beds may be reduced if polymer is used to condition the sludge
					 prior to application to the beds, or performance data from similar designs is
					 provided. Covers should extend beyond the bed area sufficiently to keep out
					 rain and snow.
1. Not less than two beds shall
					 be provided and they shall be arranged to facilitate sludge removal. Concrete
					 pads serving as vehicle support tracks should be provided for all percolation
					 type sludge beds. Pairs of support tracks for percolation type beds should be
					 on 20-foot centers.
2. Sludge
					 drying beds should be rectangular and separated from adjacent beds by permanent
					 or removable dividers. Bed width should be determined by a rational basis
					 considering the sludge handling and treatment and sludge management options. If
					 polymers or other chemicals are used to enhance sludge dewatering, the effects
					 of the polymer dosage on uniform distribution of sludge on the bed shall be
					 considered.
3. The sludge pipe to
					 the beds shall terminate at least 12 inches above the surface and be arranged
					 so that it will drain. Concrete splash plates shall be provided at sludge
					 discharge points.
4. Interior walls
					 shall be watertight and extend 15 to 18 inches above and at least 6 inches
					 below the bed surface.
5. Exterior
					 walls shall be watertight and extend 15 to 18 inches above the bed surface or
					 ground elevation, whichever is higher. They shall extend 12 to 15 inches below
					 the drain pipes.
6. The bottom of
					 the drying bed shall be relatively impervious, consisting of a minimum of
					 one-foot layer of clayey subsoil having a permeability of less than
					 one-millionth (10-6) cm/sec. In locations where the
					 ground water table is within one foot of the bottom, a watertight concrete pad
					 should be considered.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-630 - Filtration

Current through Register Vol. 40, No. 24, July 15, 2024
A. Rotary drums.
					 The following rates of vacuum filtration, in pounds of dry solids per square
					 foot of drum filter area per hour, for various types of sludge, may be
					 considered conventional loading with proper prior sludge conditioning. A
					 variable speed drive shall be provided.
Type of Treatment Process Producing Sludge Prior to
								Stabilization
Pounds of Dry Solids Per Square Foot Per Hour
								Minimum - Maximum
a. Primary
4 - 6
b. Primary and Contact Reactor
3 - 5
c. Primary and Suspended Growth Reactor
3 - 4
1. Unless
					 dual trains are provided, the following appurtenant equipment shall be provided
					 in duplicate with necessary connecting piping, and electrical controls to allow
					 equipment alternation. Spare filter fabric shall be provided except when metal
					 coils are utilized.
a. Feed pump.
b. Vacuum pump.
c. Filtrate pump.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-640 - Centrifuges

Current through Register Vol. 40, No. 24, July 15, 2024
Successful application of centrifugation similar to
						sludge thickening applications for dewatering of municipal type sludges
						requires consideration of certain design factors. Proper scale-up data
						pertaining to the particular sludge to be dewatered and the necessary polymer
						and coagulant dosage to achieve the design solids content shall be provided.
						The abrasiveness of each sludge supply shall be considered in scroll selection.
						Adequate sludge storage shall be provided for proper operation.
1. Unless dual trains are provided, the
					 following spare appurtenant equipment shall be provided, with necessary
					 connecting piping and electrical controls to allow easy installation:
a. Drive motor.
b. Gear assembly.
c. Feed pump.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-650 - Sludge pumping

Current through Register Vol. 40, No. 24, July 15, 2024
Pump capacities shall be adequate but not excessive.
						Provisions for varying pump capacity are desirable.
1. Duplicate units shall be provided where
					 failure of one unit would seriously hamper treatment works operation.
2. Positive displacement pumps or other types
					 of pumps with demonstrated solids handling capability shall be provided for
					 handling raw sludge.
3. The minimum
					 positive head necessary for proper operation shall be provided at the suction
					 side of centrifugal type pumps. A positive head of 24 inches or more may be
					 desirable for all types of sludge pumps. Maximum suction lifts shall not exceed
					 10 feet for positive displacement pumps.
4. Adequate sludge sampling facilities shall
					 be provided. Provision of quick closing sampling valves installed at the sludge
					 pumps would be an adequate means of sampling. The size of valve and piping
					 shall be at least 1-1/2 inches.
5.
					 Sludge withdrawal piping for anaerobic digesters and gravity thickeners shall
					 have a minimum diameter of six inches for gravity withdrawal and four inches
					 for pump suction and discharge lines. Where withdrawal is by gravity, the
					 available head on the discharge pipe shall be at least four feet and preferably
					 more. Also, where gravity withdrawal is to be used as the primary withdrawal
					 method, the piping for the primary sludge clarifier pump should be so arranged
					 as to permit use of the pump for removal of digested sludge. Downstream gravity
					 piping for transport of sludge shall be laid on uniform grade and alignment.
					 Slope on gravity discharge piping should not be less than 3.0%. Provisions
					 shall be made for draining and flushing discharge lines, and special
					 consideration shall be given to the corrosion resistance and continuing
					 stability of supporting systems for piping located inside the digestion
					 tank.
Statutory Authority
§ 62.1-44.19 of the Code of Virginia.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-660 - Sludge management

Current through Register Vol. 40, No. 24, July 15, 2024
Sludge management activities not specifically provided
						for through approval of design plans and specifications shall be described in a
						sludge management plan submitted by the owner to the area engineer and the DEQ
						regional office for review and approval. The use or disposal of treated sewage
						sludge shall be addressed through either the sludge management plan required by
						the VPDES permit, or a permit issued through the Virginia Pollution Abatement
						Permit Regulation (9VAC25-32) or Virginia Pollutant Discharge Elimination
						System Permit Regulation (9VAC25-31).
Statutory Authority
§ 62.1-44.15 of the Code of Virginia.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 6 - Biological Treatment › Section 9VAC25-790-680 - Rotating biological contactors

Current through Register Vol. 40, No. 24, July 15, 2024
A. The rotating biological contractor (RBC)
					 treatment process may be used to accomplish carbonaceous and nitrogenous oxygen
					 demand reductions. Expected performance of RBC equipment shall be based upon
					 experience at similar full scale treatment works or through documented pilot
					 scale testing with the particular wastewater.
B. Design. A minimum of two independent RBC
					 units shall be provided for treatment works greater than 100,000 GPD.
					 Provisions for positive and measurable flow control to individual contactors
					 shall be provided. Piping shall permit each reactor to be operated in the
					 parallel or series flow mode. The design of the RBC shaft and media support
					 structures shall assure protection from structural failure for the design life
					 of the treatment works.
1. In determining
					 design loading rates, the following parameters shall be considered: design flow
					 rate and influent waste strength; percentage of BOD5 to
					 be removed; media arrangement, including number of stages and unit area in each
					 stage; rotational velocity of the media; wastewater temperature; and percentage
					 of influent BOD5 that is soluble. The maximum first
					 stage loading shall not exceed three pounds soluble BOD5
					 per day per 1,000 square feet of media surface area.
2. The contactor basin should be designed to
					 allow a submergence of 30% to 40% based on total media surface area.
a. The clearance between the tank floor and
					 the bottom of the rotating media shall be four to nine inches to maintain
					 sufficient bottom velocities and prevent solids deposition in the
					 tank.
b. Suitable means shall be
					 provided to dewater each basin.
3. Rotating biological contactors shall be
					 covered to protect the biomass from cold temperatures and the media from direct
					 sunlight.
4. Enclosures shall be
					 constructed of corrosion resistant material. Adequate clearance shall be
					 provided for normal maintenance and reasonable access to the rotating shafts
					 and for observation of the biomass. Windows or simple louvered mechanisms shall
					 be provided for adequate equipment ventilation. To minimize condensation the
					 enclosure should be insulated or heated.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 6 - Biological Treatment › Section 9VAC25-790-690 - Suspended growth (activated sludge) process

Current through Register Vol. 40, No. 24, July 15, 2024
A. A number of variations of suspended growth
					 treatment systems can be designed, featuring combinations of reactors utilizing
					 aeration to support suspended biomass, and secondary clarifiers to separate
					 suspended solids from the secondary effluent, that are known as activated
					 sludge processes. Design standards, operating data, and experience for some of
					 these variations are not well established and may not be considered as
					 conventional design.
B. Design. The
					 possibility of nonconventional technology approval should be considered in
					 selection of a process modification. The conventional process and its various
					 modifications may be expected to consistently produce an effluent containing no
					 more than 30 milligrams per liter of either Biochemical Oxygen Demand
					 (BOD5), or total suspended solids (TSS), within the
					 boundaries of the design parameters described in this chapter and with
					 effective operation.
1. Designs to meet
					 effluent limits more stringent than conventional secondary levels will be
					 considered on a case-by-case basis when additional provisions such as flow
					 equalization, increased clarifier capacity, or other process enhancement are
					 proposed.
2. When the design
					 includes multiple suspended growth reactors or aeration basins, provisions for
					 combining the influent and return sludge and proportionally distributing the
					 combined flows to each reactor shall be included to the extent practical. When
					 the design includes multiple clarifiers, provisions for combining the effluent
					 flows from all aeration basins and proportionally distributing the basin
					 effluent with a uniform biomass concentration (mixed liquor suspended solids
					 (MLSS)) to each secondary clarifier shall be included to the extent
					 practical.
3. Effective removal of
					 grit, debris and excessive oil or grease and grinding or fine screening of
					 solids shall be accomplished prior to the activated sludge process. Aerated
					 grit chambers alone will not provide adequate solids reduction.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 6 - Biological Treatment › Section 9VAC25-790-710 - Sequencing batch reactors (SBR)

Current through Register Vol. 40, No. 24, July 15, 2024
A.
					 Usage. In accordance with the requirements of this chapter and standards
					 contained in this chapter, batch operation modifications of the activated
					 sludge process will be considered as conventional secondary treatment
					 processes. Adequate performance data and information from a full scale
					 treatment works of similar design, including the levels of influent wastewater
					 characteristics that produce hydraulic and organic loading rates within 25% of
					 values used in the proposed design, shall be provided if an SBR design is to
					 accomplish an effluent quality more advanced than a secondary level.
B. Design. The design shall meet the
					 applicable loading requirements. The operating cycle normally consists of FILL,
					 REACT, SETTLE, DRAW, and IDLE sequences with alternating sequences of mixing
					 and aeration on and off.
1. A minimum of two
					 basins shall be provided for design flows in excess of 0.1 mgd. The minimum
					 total basin volume shall be equal to the design daily influent flow volume and
					 either upstream in-line or off-line storage is necessary to minimize influent
					 flow during settling and decanting. Effective scum collection and removal
					 equipment shall be provided.
2. The
					 design basis for meeting oxygen requirements shall consider the variation in
					 liquid level depth and the aeration sequence time.
3. The basin depth shall be sufficient to
					 provide optimum separation of the settled biomass and the point of effluent
					 withdrawal.
4. Adequate mixing
					 shall be provided to resuspend settled solids at the start of the FILL sequence
					 and maintain solids in suspension over the design liquid volume
					 range.
5. A high liquid level
					 overflow shall be provided between basins. The overflow shall be located as far
					 as possible from the outlet device and in no case be closer than 10 feet from
					 the outlet device.
6. Inlets to
					 each basin shall be located as far as possible from the outlet and in no case
					 be closer than 10 feet from the outlet.
7. Scum baffles or other suitable
					 arrangements shall be provided to prevent scum from being withdrawn with the
					 effluent.
8. Outlet facilities
					 shall be designed to prevent resuspension of the settled solids in the basins.
					 An adjustable flow rate control device shall be provided on each basin
					 outlet.
9. Waste sludge control
					 facilities shall have a rate per day equal to 50% of the total basin
					 volume.
10. The FILL and DRAW
					 sequences for an individual basin shall not overlap.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 7 - Effluent Polishing and Disinfection Processes › Section 9VAC25-790-740 - Disinfection

Current through Register Vol. 40, No. 24, July 15, 2024
A. Disinfection
					 processes are designed to inactivate actual or potential pathogenic
					 microorganisms present in treated sewage effluents. Disinfection of treated
					 sewage effluents shall be provided to prevent the occurrence of public health
					 hazards in either receiving streams, land treatment sites, or reuse
					 applications from wastewater effluents. Disinfection shall be accomplished in a
					 manner that meets standards for indicator microorganisms but does not result in
					 a violation of toxicity standards.
B. Policy. The need for disinfection of a
					 sewage treatment works effluent is primarily based on standards for either the
					 receiving waters and the land application site or public exposure to reuse as
					 determined by the following requirements:
1.
					 Discharges located within 15 miles upstream or one tidal cycle downstream of a
					 water supply intake shall be disinfected at all times.
2. When sewage discharges are permitted to or
					 within five miles upstream of shellfish waters, they shall be disinfected at
					 all times.
3. Discharges located in
					 all other waters shall be disinfected at all times unless it can be
					 demonstrated, through the use of a Site Specific Beneficial Use-Attainability
					 Analysis of the recreational and other beneficial seasonal uses of the
					 receiving stream, that disinfection is not needed throughout the year, or on a
					 seasonal basis, to protect those uses.
4. Discharges for land treatment or reuse
					 purposes shall be disinfected as necessary to protect the public health and
					 welfare. The public shall not be directly exposed to treated
					 effluent.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 7 - Effluent Polishing and Disinfection Processes › Section 9VAC25-790-750 - Chlorination

Current through Register Vol. 40, No. 24, July 15, 2024
A. Disinfection can
					 be accomplished through the controlled application of chlorine compounds to
					 treated sewage to accomplish a sufficient dose, or contact exposure level, over
					 a sufficient period of time, to achieve compliance with the indicator
					 microorganism standard.
B.
					 Chemical. Conventional types of chlorine compounds (chemical) include:
1. Chlorine gas is a greenish-yellow gas with
					 a density greater than the density of air at room temperature and pressure.
					 When compressed to pressures greater than its vapor pressure, chlorine gas
					 condenses into a clear amber liquid.
2. Dry chlorine, liquid or gaseous, contains
					 no more than 150 ppm of water (by weight). Unless otherwise indicated, the word
					 "chlorine" wherever used in this section refers to dry chlorine.
3. A chlorine solution is a mixture of
					 chlorine and water.
4. A
					 hypochlorite solution is a mixture of either sodium or calcium hypochlorite and
					 water.
5. A hypochlorite tablet is
					 a solid formulation of a hypochlorite compound designed to dissolve in a liquid
					 at a controlled rate.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 7 - Effluent Polishing and Disinfection Processes › Section 9VAC25-790-760 - Bromochlorination

Current through Register Vol. 40, No. 24, July 15, 2024
A. Disinfection by
					 bromochlorination is accomplished with bromine chloride (BrCl) in a manner
					 similar to chlorine disinfection. Bromine chloride is an equilibrium mixture of
					 bromine and chlorine in both the gas and liquid states. The chemical is highly
					 soluble in water and hydrolyzes to hypobromous (HOBr) and hydrochloric (HCL)
					 acids. Due to the rapid decay of bromine chloride in wastewater, generally
					 there will not be any measurable bromine chloride residuals in the final sewage
					 effluents. Pure bromine chloride is a heavy, fuming, dark, red liquid which is
					 about 20% disassociated into molecular bromine and chlorine.
B. Design. This disinfection process can be
					 considered for treated effluents with BOD5 and suspended
					 solids concentrations of 30 mg/l or less. Prior documentation should be
					 furnished which shows that adequate disinfection of a specific sewage effluent
					 can be obtained with this process.
C. Dose control. Bromochlorination feed
					 equipment capacity shall be based on degree of treatment, flow variations, and
					 other uses in the treatment processes. For disinfection, the capacity shall be
					 adequate to produce the control point residual required in the permit or
					 certificate issued. The dosing capacity of this process for normal domestic
					 sewage should usually be 80% of that recommended in the chlorine dosage Table
					 7.
1. Bromochlorination equipment and spare
					 parts are essentially the same as similar requirements for
					 chlorination.
2. Gas feeder systems
					 may be used for feed rates less than 500 pounds per day. Direct liquid bromine
					 chloride feed systems should be used for feed rates greater than 500 pounds per
					 day.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 7 - Effluent Polishing and Disinfection Processes › Section 9VAC25-790-770 - Ultraviolet light irradiation (UV)

Current through Register Vol. 40, No. 24, July 15, 2024
A. Disinfection can be achieved through
					 exposure of microorganisms to a sufficient level of UV at the germicidal
					 wavelength for an adequate period of time.
B. Design parameters. The following
					 parameters are important to UV disinfection design:
1. The absorbance coefficient is a measure of
					 the UV absorbing characteristics of the irradiated fluid as measured by a
					 single beam spectrophotometer at 253.7 nanometers, using both filtered and
					 unfiltered fluid samples. The units of this parameter are absorption units per
					 unit distance from the UV source.
2. The contact period is the period of time
					 that a microorganism is exposed to a given intensity and is a function of the
					 residence time distribution (RTD) of flow moving past an arrangement of UV
					 lamps which can be determined from tracer tests.
3. The UV dose is a function of the product
					 resulting from multiplying the average UV intensity, by the contact period (T)
					 and is expressed as (microwatts)(seconds)/square centimeter
					 (UW/SQ.CM/SEC).
4. The dose
					 response is a measure of the inhibition of cell replication, and is indicated
					 by the ratio of the monitored log counts of an indicator organism prior to and
					 following exposure to a given UV dose.
5. The dispersion coefficient (E) is a
					 measure of turbulent mixing (square centimeters per second) within the fluid
					 passing through an arrangement of UV lamps. The value of E established by the
					 RTD variance should be correlated with the contact time necessary to provide
					 the required dose response.
6. The
					 intensity is an expression of the rate (units of microwatts per square
					 centimeter) at which energy is delivered from the source into the surrounding
					 liquid. UV intensity will dissipate by dilution and will be absorbed by the
					 medium as the distance from the source increases. The UV intensity provided for
					 disinfection purposes should be approximated on the basis of the physical
					 properties of the UV lamps, the physical arrangement of lamps within a flowing
					 liquid stream, and the properties of the wastewater effluent (Kab).
7. Lamp assemblies are defined as the
					 arrangement or grouping of UV lamps occupying the cross-section of a channel or
					 reactor.
8. Photoreactivation is a
					 process whereby certain organisms regain the ability to reproduce upon exposure
					 to secondary light.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 7 - Effluent Polishing and Disinfection Processes › Section 9VAC25-790-780 - Ozonation

Current through Register Vol. 40, No. 24, July 15, 2024
A. Disinfection can
					 be achieved through microorganism exposure to a sufficient level of Ozone (O3)
					 in solution for a proper contact period. Ozone is an unstable gas that is
					 produced when oxygen molecules are dissociated into atomic oxygen which
					 subsequently collides with other oxygen molecules.
B. Parameters. The following parameters are
					 important factors in the design of ozonation disinfection:
1. The applied ozone dosage is the mass of
					 ozone from the generator that is directed to a unit volume of the wastewater to
					 be disinfected.
2. The transferred
					 ozone dosage is the mass of applied ozone that is dissolved into the
					 wastewater. This dosage depends on the physical characteristics of the
					 contractor and the residual ozone concentration, which is affected by the
					 quality of the wastewater.
3. The
					 dew point is the measure of the relative moisture content of a gas,
					 specifically the temperature at which a gas under a precise pressure is
					 saturated with water.
4. Off-gas is
					 the excess ozone transferred from the contact basin to the surrounding
					 atmosphere.
5. Ozone destruction
					 involves the changing of ozone to a less reactive molecule. This occurs
					 naturally because of ozone's inherent instability. However, deactivation by
					 thermal or catalytic destruction units is usually necessary to reduce excess
					 ozone in the off-gas to acceptable levels for human health.
6. Dose/response curve is a mathematical
					 relationship between coliform destruction and transferred ozone dosage. A
					 threshold level of dosage may exist that indicates no response until the dosage
					 exceeds that threshold.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 7 - Effluent Polishing and Disinfection Processes › Section 9VAC25-790-800 - Dechlorination

Current through Register Vol. 40, No. 24, July 15, 2024
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 7 - Effluent Polishing and Disinfection Processes › Section 9VAC25-790-820 - Postaeration

Current through Register Vol. 40, No. 24, July 15, 2024
A. Postaeration
					 design may involve mechanical aeration, diffused air injection, or cascade type
					 aeration. Other methods may be utilized and will be evaluated on a case-by-case
					 basis by the department.
B.
					 Mechanical aeration. Multiple aeration basins for continuous operability should
					 be provided at all treatment works with a design flow of 40,000 gallons per day
					 or more, unless other means of maintaining an adequate level of dissolved
					 oxygen (D.O.) in the effluent are available.
1. The aeration equipment transfer efficiency
					 shall be determined utilizing the manufacturer's certified rating for the
					 particular equipment being considered. The transfer efficiency shall be
					 adjusted to reflect anticipated field conditions of temperature, atmospheric
					 pressure, initial D.O., and composition of the wastewater being oxygenated.
					 When the detention time within the aeration basin exceeds 30 minutes,
					 consideration shall be given to oxygen requirements resulting from biological
					 activity in the postaeration basin. For aeration basins equipped with a single
					 mechanical aeration unit, a minimum of one mechanical aeration unit shall be
					 maintained in storage at the treatment works site for immediate
					 installation.
2. Aeration basins
					 shall be designed to minimize short circuiting of flow and the occurrence of
					 dead spaces. Vortexing shall be prevented.
Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 8 - Advanced Treatment › Section 9VAC25-790-830 - Flow equalization

Current through Register Vol. 40, No. 24, July 15, 2024
A. Flow
					 equalization is a unit process whereby the variability of wastewater flows, in
					 terms of volume and strength, is lessened. Where flow equalization is utilized
					 within a sewerage system or treatment works to reduce the peak flow conveyed
					 to, or processed by, the treatment works, the performance of the treatment
					 process should be improved in relation to the estimated conventional effluent
					 values. The ability of a treatment works that is provided with flow
					 equalization to meet permit or certificate effluent limitations shall be
					 evaluated on a case-by-case basis.
B. Usage. Flow equalization shall be provided
					 in the flow scheme ahead of advanced chemical-physical processes, unless
					 engineering analysis shows that absence of flow equalization is more cost
					 effective while maintaining the same degree of reliability and operational
					 control.
1. Flow equalization should be
					 provided upstream of biological treatment works designed to process a mean
					 daily flow of 0.1 mgd or less, and receiving hourly peak flows in excess of
					 twice the design flow, if such peak flows will occur daily in excess of 50
					 times annually.
2. Flow
					 equalization shall be provided upstream of biological treatment works designed
					 to process a mean daily flow of 0.1 mgd or less that are permitted with
					 effluent limitations less than 20 mg/l of BOD5 or TSS,
					 or a TKN of less than 5 mg/l, or a total phosphorus of less than 2 mg/l, unless
					 approved downstream unit operations are also provided.