PURPOSE: This rule specifies the minimum standards for the design of supplemental treatment processes that are part of wastewater collection and treatment systems. This rule is to be used with rules 10 CSR 20-8.110 through 10 CSR 20-8.210. It does not address all aspects of design, and the design engineer may refer to other appropriate reference materials so long as these minimum standards set forth in this rule are met.

Editor’s Note: The secretary of state has determined that the publication of this rule in its entirety would be unduly cumbersome or expensive. The entire text of the material referenced has been filed with the secretary of state. This material may be found at the Office of the Secretary of State or at the headquarters of the agency and is available to any interested person at a cost established by state law.

1. (1) Applicability. Wastewater systems that utilize supplemental treatment shall be designed based on criteria contained in this rule, published standards, applicable federal and state requirements, standard textbooks, current technical literature and applicable safety standards. In the event of any conflict between the above criteria, the requirement in this rule shall prevail.

   1. (A) This rule shall not apply to treatment units covered in 10 CSR 20-8.300.
   2. (B) This rule shall not apply to treatment units covered in 10 CSR 20-8.500.

2. (2) Polishing Reactors.

   1. (A) Design. The process shall—

      1. 1. Provide a minimum hydraulic reten-

tion time of three (3) hours;

1. 2. Be based on actual reactor influent

characteristics;

1. 3. Be based on Biochemical Oxygen

Demand loading rate of forty-eight pounds per one thousand cubic feet per day (48 lbs BOD/1,000 cf/day) or less;

1. 4. Be sized using less than two tenths a

pound TKN per one thousand square feet per day (0.2 lbs TKN/1,000 ft2/day) when nitrifying;

1. 5. Provide sufficient alkalinity with a

minimum residual of fifty milligrams per liter (50 mg/L) in the effluent or include chemical treatment;

1. 6. Include cold weather provisions, such

as heaters, insulated covers, installation of temperature controlled enclosures for aboveground components to prevent freezing and to ensure ammonia removal; and

1. 7. Provide a blower malfunction alarm

able to notify the operator of alarm activations through audio-visual means.

1. (3) Filtration.

   1. (A) Filtration systems shall be preceded with additional process, such as chemical coagulation and sedimentation or other acceptable process, when:

      1. 1. Permit requirements for total sus-

pended solids (TSS) are less than ten milligrams per liter (10 mg/L);

1. 2. Effluent quality is expected to fluctu-

ate significantly;

1. 3. Significant amounts of algae are pre-

sent; or

1. 4. The manufacturer recommends an

additional process.

1. (B) General Design.

   1. 1. Filtration systems shall have:

      1. A. Convenient access to all compo-

nents and the media surface for inspection and maintenance without taking other units out of service;

1. B. Enclosed controls and heating and

ventilation equipment to control humidity; and

1. C. The capacity to process the design

average flow to the filters with the largest unit out of service utilizing a minimum of two (2) units.

1. 2. Flocculation. For filtration systems

requiring coagulation and flocculation prior to the filtration, the flocculation system shall:

1. A. Include chemical feed equipment

to meet the system’s anticipated peak design flow and the ability to proportion chemical feed rates; and

1. B. Ensure the rapid dispersion and

mixing of chemicals throughout the wastewater by providing mechanical or in-line static mixers.

1. (C) Deep bed filters.

   1. 1. The design of manifold type filtrate

collection or underdrain systems shall:

1. A. Minimize loss of head in the man-

ifold and baffles;

1. B. Provide the ratio of the area of the

underdrain orifices to the entire surface area of the filter media at about three one-thousandths (0.003);

1. C. Provide the total cross-sectional

area of the laterals at about twice the area of the final openings; and

1. D. Provide a manifold that has a min-

imum cross sectional area that is one and one half (1.5) times the total area of the laterals.

1. 2. All rotary surface wash devices shall

provide adequate surface wash water to provide one half to one gallon per minute per square foot (0.5-1.0 gpm/ sq ft) of filter area.

1. (D) Shallow bed filters. The shallow bed filter shall:

   1. 1. Comply with the manufacturer’s rec-

ommendations at average design flow;

1. 2. Provide multiple unit operations to

allow for continuous operability and operational variability;

1. 3. Consist of a series of up to eight inch

(8") filter increments having a minimum total media depth of eleven inches (11"), if using filter media except for sand media.

1. 4. Have an effective size in the range of

four-tenths millimeter to sixty-five hundredths millimeters (0.40 mm-0.65 mm) and a uniformity coefficient of one and one half (1.5) or less, if utilizing sand media;

1. 5. Include inlet ports located throughout

the length of the filter.

1. 6. Provide an underdrainage system

along the entire length of the filter so that filter effluent is uniformly withdrawn without clogging outlet openings.

1. 7. Have a traveling bridge mechanism

which—

1. A. Provides support and access to the

backwash pumps and equipment;

1. B. Is constructed of corrosion resis-

tant materials;

1. C. Provides for consistent tracking of

the bridge;

1. D. Provides support of the power

cords; and

1. E. Initiates a backwash cycle automat-

ically when a preset head loss through the filter media occurs.

1. (E) Cloth/Disc Filters.

   1. 1. Media Design. The media shall:

      1. A. Have an average pore size of no

larger than thirty (30) microns;

1. B. Follow the manufacturer’s recom-

mendations; and

1. C. Be chemical-resistant if the filter

will be exposed to chemicals, such as chlorine or disinfectants.

1. 2. Filtration Rates and Hydraulics. The

design shall—

1. A. Base the filtration rate on the

effective submerged surface area of the media and provide a maximum filtration rate for peak flow of not more than six and one half gallons per minute per square foot (6.5 gpm/sq ft) of submerged cloth media; and

1. B. Be able to treat the design flow rate

with one (1) filter unit in backwash mode.

1. (4) Microscreening.

   1. (A) Screen Material. The microfabric shall be a material demonstrated to be durable through long-term performance data.
   2. (B) Backwash. All backwash shall be recycled for treatment.

2. (5) In-stream Diffusers.

   1. (A) General.

      1. 1. The mixing zone shall not encroach

on a drinking water intake, recreation area, or sensitive habitat, overlap the next downstream outfall, or occlude a downstream tributary.

1. 2. Diffuser installation requires notifica-

tion and an Army Corps of Engineers permit.

1. (B) Diffuser Design Criteria.

   1. 1. The pipeline shall be contained with-

in approved property boundaries or easements.

1. 2. Maximum port velocity shall not

exceed fifteen feet per second (15 fps).

AUTHORITY: section 644.026, RSMo 2016.* Original rule filed Aug. 10, 1978, effective March 11, 1979. Amended: Filed June 15, 2018, effective Feb. 28, 2019. *Original authority: 644.026, RSMo 1972, amended 1973, 1987, 1993.