Glenn AffleckCEng, MIChemE, Assoc. DBIADesign Manager

Upgrading Solids Dewatering at Rehoboth Beach WWTP

Background01Project Drivers02Project Scope03Dewatering Building04

Waste Sludge Holding Tanks05Construction Sequencing 06Next Steps07

Background

Plant Located in Sussex County, DESeasonal PopulationInfluent Flows

Criteria Winter SummerMax

Historical Month

Permitted

Influent Flow (MGD) 0.65 1.75 2.18 3.4

– Biosolids are aerobically digested and thickened to 1-1.5%– Land Applied for Disposal– Labor intensive and unreliable– County wide approach to management of biosolids– Regional Dryer system at Inland Bays Regional Wastewater Facility (IBRWF)

Project Drivers

– Phased CIP Upgrade currently ongoing at the plant– This project is Phase 3B of this upgrade and is the second to last phase of the

upgrade– Phase 3B Scope

• Demolish Gravity Thickener• Build new Biosolids Dewatering Building• Convert Aerobic Digesters to Waste Sludge Holding Tanks (WSHT)• Miscellaneous upgrades to other plant components as necessary to support these

new process areas

Project Scope

Project Scope – Existing Conditions

Sludge Thickener

Aerobic Digesters

Project Scope – After Dewatering Upgrade

New Dewatering Building

Waste Sludge Holding Tanks

Washwater Supply Pumps

Dewatering Building

Container Room

Blower Room

Sludge Pump Room

Electrical Room

Filter Press Room

Waste Sludge Holding Tanks

Demolish:‒ Catwalks‒ Agitators‒ Air piping

Air Diffuser System

Decant Pumps

– Project requires demolition of thickener– City needs to be able to dispose of sludge during operation– Unthickened sludge would require up to 9 trucks per day during an average summer

and up to 11 trucks per day on the average max historical month– Need to maintain some thickening capability during construction

Construction Sequencing

Title 2Example

T-6A

T-6B

T-7 B-3 Pumps

T-9CFrom PS-1

Truck Fill

B-3 Blowers

City Drains T-6A

T-6A

T-6B

From PS-1

T-7 B-3 Pumps

T-9CFrom PS-1

Truck Fill

B-3 Blowers

Convert to WSHT

Temp Suction Pipe

Construction Sequencing

Title 2

Construction Sequencing

T-6A

T-6B

From PS-1

T-7B-3

Pumps

T-9CFrom PS-1

Truck Fill

B-3 Blowers

Temp Suction Pipe

Temp Blower

Demo T-7

T-6A

T-6B

From PS-1

B-3 Pumps

T-9CFrom PS-1

Truck Fill

B-3 Blowers

Temp Suction Pipe

Temp Blower

B-7 Dewatering

Building

B-7 Blowers

Title 2Example

Construction Sequencing

T-6A

T-6B

From PS-1

T-9C

From PS-1

Truck Fill

B-7 Blowers

B-7 Dewatering Building

Cake

Convert to WSHT

B-3 Pumps

B-3 BlowersT-6A

T-6B

From PS-1

T-9CFrom PS-1

Truck Fill

B-7 Blowers

B-7 Dewatering Building

Cake

– Design is complete and awaiting bidding– Phase 2 to be completed prior to commencing Phase 3B construction– At this stage looking at commencing construction in Q2 2022

Next Steps

Thank You