Brief Project Description
The Town of Berryville owns and operates a lagoon treatment system, which has a current design flow of 0.45 MGD; the discharge is to the Shenandoah River. The project includes replacement of the existing lagoon with a new 700,000 gallon/day state of the art facility.
Based on a present worth comparison of Nutrient Reduction Technology (NRT) options, the Membrane Bioreactor (MBR) system was ultimately selected due to cost-effectiveness and future expandability.
The scope of the project was detailed in the Preliminary Engineering Report completed in April 2008 and the project will include the construction of the following key (grant eligible) components:
Preliminary Treatment: New influent rotating drum screen fine screen (partially eligible) and screw type conveyor. A coarse bar screen and grit removal are also proposed (neither are eligible).
Flow Equalization (partially grant eligible): A precast concrete tank is proposed to catch the excess flow between the peak forward flow (2.1 MGD) and the design maximum day flow. The sizing of the equalization structure prior to detailed design is 1.5 million gallons.
Secondary Treatment (partially grant eligible): New bioreactor basins (BRB) will be constructed, such that the activated sludge plant will operate in a 3 stage configuration for NRT treatment. Each parallel treatment train will include: (1) primary anoxic zone for denitrification; (2) aerobic zone for nitrification; and (3) secondary anoxic zone for denitrification. Respectively, the volumes (in gallons) for each zone are 110,000, 450,000, and 75,000; thus, 29% of the reactor volume is anoxic (grant eligible for fine screens). Two parallel membrane filtration reactors (specifics not yet available) will follow the bioreactor.
The aeration system consists of 3 variable speed blowers that provide low pressure air to the fine bubble air diffuser system. There are two recycle streams in the biological treatment system: Nitrified Recycle (NRCY) and return activated sludge (RAS). The NRCY will be pumped by submersible pumps installed directly in the primary anoxic zone and RAS will be returned by gravity from the MBR to the head of the aerobic zone.
Membrane Filtration (partially grant eligible): Two parallel MBR trains will follow the bioreactor. The Membrane Filtration System will rely on 3 air blowers to agitate the membrane fibers and remove accumulated solids from the fibers; 3 permeate pumps are also provided.
Solids Train (partially grant eligible): Two parallel tanks with diffused aeration are provided for solids digestion. Digested sludge would be conveyed to a lime feed facility, after which it would be dewatered via belt filter presses with a polymer feed system.
Chemical Feed Systems: A new methanol storage and feed system will be installed to provide supplemental carbon to the denitrification process; chemical storage and feed for phosphorus reduction is also included in this project.
Electrical and Process Control (partially grant eligible) - Install a PLC process control system that will perform monitoring of processes including the chemical feed systems, dissolved oxygen, MBR operations, and other additional monitoring and control necessary for nutrients. An emergency generator and automatic transfer switch will be installed at the facility.