Section 370.915 Rotating Biological Contactors

Section 370

Section 370.915  Rotating

Biological Contactors

a)         General

Wastewater treatment facilities that propose to use rotating

biological contactors (RBCs) shall submit to the Agency for review field

experience and operational data that demonstrates that observed problems with

the process have been solved at similar full scale installations.  The Agency

will review the claimed field experience against known field conditions and the

operational history of observed problems at similar facilities.

b)         Mechanical Reliability and Structural Integrity

1)         The mechanical and structural reliability of the shafts and

media subjected to cyclic stress reversals must be demonstrated relative to the

design life of the plant and the known weight of the machines based on field

experience.

2)         The design must show that film thickness will be effectively

controlled throughout all parts of the media pack to prevent excessive film

weight and water pickup weight due to plugging restrictions.  The equipment

design must include load cells to warn of the need for film thickness control

and to demonstrate the effectiveness of the proposed film thickness control

practices.

c)         Process Reliability

1)         Process reliability must be demonstrated, including proven

operational control procedures relative to design organic loadings for the unit

media area or volume, which satisfactorily insure that the applicable effluent

standards are met.  The process design shall also include proven operational

control procedures that will prevent process functional deficiencies and media

plugging that cause the weight to exceed shaft and media structural

capabilities during the design life of the plant.

2)         The design must show that adequate void clearance (as

distinguished from void ratio) is provided to insure that the biological film,

including any grease and fats that may accumulate, will not interefere with the

flow of liquid and air in the media pack

es and media

plugging that cause the weight to exceed shaft and media structural

capabilities during the design life of the plant.

2)         The design must show that adequate void clearance (as

distinguished from void ratio) is provided to insure that the biological film,

including any grease and fats that may accumulate, will not interefere with the

flow of liquid and air in the media pack.  The Agency will compare the RBC

designs under review to past experience with designs used for plastic trickling

filter media to accomplish adequate void clearance.

3)         The design shall provide for maintaining a minimum of 2.0 mg/l

dissolved oxygen in the basin liquor.  The effectiveness of the proposed method

for maintaining adequate dissolved oxygen will be evaluated based on field

experience at similar full scale installations.

4)         If pilot testing is proposed, the size of the RBC pilot plant

unit and the scope and duration of the testing program on the specific waste

that will be treated must be thoroughly documented.  The proposed pilot testing

program should be submitted to the Agency for comment prior to the initiation

of testing.  The RBC pilot units must be of prototype scale.  Because of

differential seasonal weight and plugging field problems, the test period must

cover the four seasons, to allow the Agency to evaluate the proposed design

against the experience of existing full scale plants.

5)         The process design must include provisions for meeting

applicable effluent limits with some units out of service for unit repair,

biofilm thickness control, out-of-balance correction and other operational

problems. Added units for standby credit will be required to insure compliance

with effluent limitations and to prevent mechanical or structural failures

during periods of unit outage for maintenance, repair, or process control

purposes.