Digester Cleaning –Top Ten List

Presented By:

Tricia Butler, PE, RMC Water and EnvironmentJohn Jardin – Operations Superintendent,

Encina Wastewater Authority

Average Daily Flow – 28 mgd Digester Nos. 5 & 6 g

Cleaned May 2003 Pump Mixing System

EncinaWastewater

Authority

95-ft diameter, 42.8-ft side t d th (2 05 ) 94 sludge trailers

Authority

water depth (2.05 mg)800,000 gal digester volume

Contractor-removed

94 sludge trailers50 cubic yards of plastics

and debris land-filled

Average Daily Flow – 3 75 mgd

Digesters 1, 2, 3 and 4 –July 2004

3.75 mgdCleaned July 2004

Gas Mix System converted to Pump Mix

Yucaipa Valley Water

District

45-ft diameter, 22-ft side water depth 48 t k l d f l d

District

water depth760,850 gallons digester

volume removed

48 truck loads of sludge removed

Digester CleaningDigester Cleaning

Top Ten Questions to ask yourself when you want to clean your digesters.

Q. 10 – How do you decide whoQ. 10 How do you decide who will clean your digesters?

Your own staff?

Advertise for bids

Request proposals

Combination staff & Contractor

I f ti t C t tInformation to Contractor

Digester Quantity and Quality of sludge

RFP –- Configuration

- access

Quality of sludgeLab Data

proposal requirements

Purchasing InfoExperience

requirementsScopep

Oth S i b C t tOther Services by Contractor

Lighting forLighting for inspection or during repairs

Odor Control

Provision of confined

spaceGround-

waterspace entry for inspector

water dewatering

Q. 9 - What are your SchedulingQ. 9 What are your Scheduling and Sequencing Constraints?

Gas Production

DW Capacity -Reseeding

Digesters p yEquipmentDigesters

Treatment Require-ments

Staff Schedule ments

Q. 8 - What else do you want toQ. 8 What else do you want to do while digesters are down?

InspectionProcess - mixing performanceProcess mixing performanceCoatingEquipmentEquipmentStructural

Documentation Photos Documentation - Photos Repairs

Inspect Condition of Coating and Structural

D t diti f lDocument condition of seals and location of equipment

Access

Pumping and ScreeningScreening

Dewatering Equipment

Polymer Blending and Storage

ContractorContractor Plant Entrance

Q. 6 - How will equipmentQ. 6 How will equipment be powered?

Contractor Provided• Generator• Air Permitting

Owner Provided• Spare Capacity / Location• Cost of Power CableCost of Power Cable

Q. 5 - What about washdownQ. 5 What about washdown water and centrate?

Location, quantity Accepting centrate

and other side Quality - screening, q yand quality of

washdown water available.

and other side streams.

Capacity of plant drainage system

Quality screening requirements.

Impact on process

Q. 4 - What are safetyQ. 4 What are safety requirements?

Agency Policy - Confined

Contractor Provide Co ed

Spaceo de

Safety Plan

Q. 3 - How do you handle airQ. 3 How do you handle air and gas during start-up?

Air quality considerations Cogeneration requirements Cogeneration requirements Quality of GasQuantityQuantity

Combustion potential Sludge in - gas out

Q. 2 - Where will the dregs ofQ. 2 Where will the dregs of the digester go?

Contractor Handle,Agency Paperwork

Agency ContractAgency Contract

After sludge, plastics, grit, struvite

Q 1 Sh th !Q. 1 – Show me the money!Sludge StandbySludge Volume

Standby Time

Metered sludge Include No. of Days

in RFPless wash-down

water

in RFPStart-up between

tanks

Calculate volume at start of cleaning

B bid ithTime for inspection,

repair ventilationBase bid with adjustment

repair, ventilation

QuestionsQuestions