PURPOSE: This rule specifies the minimum standards for the design of preliminary treatment units 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 preliminary 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) General. All wastewater treatment facilities must have a screening device, comminutor, or septic tank for the purpose of removing debris and nuisance materials from the influent wastewater.
3. (3) Grease Interceptors. Grease interceptors shall be provided on kitchen drain lines from 10 CSR 20-8

institutions, hospitals, hotels, restaurants, schools, bars, cafeterias, clubs, and other establishments from which relatively large amounts of grease may be discharged to a wastewater treatment facility owned by the grease-producing entity. Grease interceptors are typically constructed from fiberglass reinforced polyester, high density polyethylene (HDPE), or concrete. For corrugated HDPE grease interceptors, follow ASTM F2649 – 14 Standard Specification for Corrugated High Density Polyethylene (HDPE) Grease Interceptor Tanks, as approved and published September 1, 2014. For precast concrete grease interceptor tanks, follow ASTM C1613 – 17 Standard Specification for Precast Concrete Grease Interceptor Tanks, as approved and published September 1, 2017. These standards shall hereby be incorporated by reference into this rule, as published by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428- 2959. This rule does not incorporate any subsequent amendments or additions.

1. (4) Screening Devices.

   1. (A) General.

      1. 1. Freeze protection. All screening

devices and screening storage areas shall be protected from freezing.

1. 2. Provisions shall be made for isolating

or removing screening devices from their location for servicing.

1. 3. Safety.

   1. A. Railings and gratings.

      1. (I) Manually cleaned screen chan-

nels shall be protected by guard railings and deck gratings with adequate provisions for removal or opening to facilitate raking.

1. (II) Mechanically cleaned screen

channels shall be protected by guard railings and deck gratings. Give consideration to temporary access arrangements to facilitate maintenance and repair.

1. B. Mechanical devices.

   1. (I) Mechanical screening equip-

ment shall have adequate removal enclosures to protect facility personnel against accidental contact with moving parts and to prevent dripping in multi-level installations.

1. (II) A positive means of locking out

each mechanical device shall be provided.

1. (III) An emergency stop button

with an automatic reverse function shall be located in close proximity to the mechanical device.

1. C. Electrical Equipment, Fixtures,

and Controls. Electrical equipment, fixtures, and controls in screening area where hazardous gases may accumulate shall meet the requirements of the electrical code referenced in 10 CSR 20-8.140(7)(B).

1. (B) Screens. Where two (2) or more mechanically cleaned screens are used, the design shall provide for taking the largest unit out-of-service without sacrificing the capability to handle the average design flow. Where only one mechanically cleaned screen is used, it shall be sized to handle the design peak instantaneous flow.

1. (5) Comminutors. Provisions for location and safety shall be in accordance with screening devices, paragraph (4)(A)3. of this rule.

2. (6) Grit removal facilities are required for wastewater treatment facilities that—

   1. (A) Utilize membrane bioreactors for secondary treatment;
   2. (B) Utilize anaerobic digestion;
   3. (C) Receive wastewater from combined sewers; or
   4. (D) Receive wastewater from collection systems that receive substantial amounts of grit.

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.