Digester Cleaning – Top Ten List Presented By: Tricia Butler, PE, RMC Water and Environment John Jardin – Operations Superintendent, Encina Wastewater Authority
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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
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