Rockland County Sewer District, Energy Studies and Cogeneration Conversion Strategic Partner with Siemens Industry, Inc. to Implement an Energy Performance Contract

Posted on June 17, 2015

Client: Rockland County Sewer District
Location: Orangeburg, New York
Project Period: 2013
D&B Project Manager: Ronald C.Delo, P.E., BCEE
Project Cost: $11,400,000

Major Components

Design and Construction Phase Services, Construction Scope of Work, Packaging and Delivery

  • Rehabilitation of Anaerobic Digester Tanks and Equipment
  • In-depth evaluation of energy/gas production capability
  • Added high efficiently digester mixing systems
  • Prepared and received a NYSERDA grant application for cogeneration system
  • Combined Heat and Power System
  • Upgrade Studied conversion of digester gas to cogeneration system
  • Replaced floating gas holder cover
  • Lighting & Lighting Controls Upgrades
  • Digester Gas Cleaning System Installation
  • Rotating Biological Contractors (RBC) Optimization
  • Biogas Metering Improvements
  • Boiler Control Improvement
  • VFD Replacements Process Systems (Influent Pumps)
  • VFD Replacements Process Systems (Centrifuges)
  • Building Management System
  • Building Envelope Improvements

Project Description

RC WWTP 1Rockland County Sewer District No. 1 (RCSD) Wastewater Treatment Plant provides sewage treatment services to the Towns of Ramapo and Clarkstown and several parcels in the Town of Orangetown. The District’s wastewater treatment facility is located in Orangeburg, New York. The Wastewater Treatment Plant was originally constructed in 1967 to treat 10 MGD, and was expanded to 28.9 MGD in the mid 1980’s. The treatment process consists of mechanical bar screens, aerated grit chambers, primary settling tanks, rotating biological contractors, secondary settling tanks and chlorine contact tanks. Sludge is managed in two 90-foot diameter anaerobic digester tanks. Methane gas is collected and stored (up to 50,000 cf/day) and will ultimately be used for electric generation. Treated, chlorinated effluent is discharged into the Hudson River.

Dvirka & Bartilucci Consulting Engineers (D&B) is a strategic partner with Siemens Industry Inc. to implement an energy performance contract for RCSD#1. D&B will be providing analyses of RCSD’s existing wastewater treatment plant systems to identify areas where facility improvement measures can be made that will improve operational performance and efficiency and reduce energy usage and O&M costs. D&B will then design the facility improvement measures selected by RCSD for implementation.

The major component of this project will be the installation of a new, higher capacity cogeneration system with heat recovery, gas conditioning and measurement. The facility improvement measures implemented under this project will be paid for from guaranteed savings generated from the improvements.

Estimated Budget at Time of Bid

Actual Construction Cost
N/A at this time. Construction not yet completed.

Project Schedule

Specific Techniques or Unique Methods employed to explore design options, determine estimated construction costs, and/or monitor construction.

D&B has developed the volumetric loading calculations for the methane gas expected to be generated from the anaerobic digester system and developed a design for electrical generation and heat recovery. The anticipated methane gas flow rate was in the range of 150 cfm to 180 cfm which will generate up to 675 kw-hours of power, about 40% of the plants capacity. D&B validated the design calculations using plant laboratory results (volatile solids destruction, percent solids, etc.). For this design planning, D&B has evaluated micro turbine generation systems as well as combustion engines and has developed design layouts using Kraft, Jenbacher, MWM, Liebherr and other leading engine suppliers. Methane gas conditioning was also planned in the design for siloxane removal, moisture removal and hydrogen sulfide treatment. D&B partnered with the leading methane gas conditioning manufacturers in the field and developed a process flow diagram to first removed moisture and hydrogen sulfide from the gas and then, subsequent to storage, removed siloxane. Prior to the gas entering the engine it is pre heated using waste heat from the engine for one final moisture removal step. D&B calculated the heat recovery achievable in this system utilizing the waste heat from the engine. Through a series of heat exchangers, approximately 200 gpm of hot water at a temperature of 190ºF can be captured and re-used to heat the incoming digester sludge and also be used to provide space heat for the garage areas and certain maintenance rooms further improving on energy savings. D&B contacted the local power supply companies to develop a system and program necessary to ensure the electrical power generation meets the needs of the local provider and has the necessary safeguards to protect the service.

Other FIMs D&B has identified that will result in energy and operational savings at Rockland County Sewer District that can be further investigated during the IGEA Phase are as follows:

  • Dewatering System Improvements
  • Odor Treatment System Improvements
  • Insulate Digester Tank Covers
  • Sudge Thickening Optimization
  • Hydropower
  • FOG Receiving Station
  • Geothermal
  • Solar Power System
  • Wind Power
  • Emergency Generator Peak Shaving
  • Smart Grid Technology
  • Demand Response Program
  • Utility Procurement
  • Electric Car Charging Station
  • Energy Star and LEED
  • Transformer Replacement

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