WATER – ENERGY NEXUS WASTEWATER – ENERGY STAGE

Presented by Adim Altalibi

CEM, CHMM

June 27, 2013

Water – Energy Nexus

Table of Contents:

• Water cycles, use and the energy

• Wastewater treatment processes

• Wastewater plant energy use

• Energy efficiency opportunities

• Case studies

Water – Energy Nexus Urban Water Life-Cycle

Providing water and wastewater (W&WW) services involves extracting, moving and treating water

Energy plays role in the following stages: Drinking water processes

Customer use

Wastewater (WW) processes

Regulatory Requirements: SDWA, CWA

Water – Energy Nexus Key Stages of the Urban Water Lifecycle

Water – Energy Nexus Life-Cycle Energy Utilization Water Treatment Plant – Ann Arbor : Total capacity = 50 MGD Average flow delivered = 14 MGD (6 years of data) Average electric energy consumed/MG treated = 2389

kWh/MG Wastewater Treatment plants – Detroit: Secondary treatment capacity = 960 MGD Primary Treatment capacity = 1700 MGD Average WW flow treated = 660 MGD (3 years of data) Average electric energy consumed/MG treated = 1100

kWh/MG (Largest WWTP in Michigan, and largest single site in the US)

Water – Energy Nexus Wastewater Treatment:

What is WW

Why treating WW

How is it generated

How is it collected

(Smaller sewers, gravity systems, pump and lift stations,

combined sewers)

Inflow and Infiltration (I&I)

Water – Energy Nexus Processes of a Wastewater Treatment Plant

(WWTP):

1. Preliminary Treatment

2. Primary Treatment

3. Secondary Treatment

4. Advanced Treatment

5. Tertiary Treatment

Water – Energy Nexus Typical Wastewater Treatment Process

Water – Energy Nexus

Water – Energy Nexus Lowering Energy Consumption and Cost

• Improving energy efficiency

• Implementing renewable energy

• Planning O&M

Energy Use:

1. Collection systems

2. Within WWTP – point of interest

3. Outside WWTP

Energy/ Fuel types

Water – Energy Nexus

Operations/Processes major energy consumers 1. Preliminary and Primary Treatment • Electric drives • Various types of pumps • Pre-aeration equipment (circumstantial)

2. Secondary Treatment • Electric drives • Mixers/Mechanical aerators • Various types of pumps • Blowers

Water – Energy Nexus 3. Tertiary Treatment

• Electric drives

• Mixers/Mechanical aerators

• Various types of pumps

• Blowers / Compressed air

4. Advanced Treatment & Disinfection

• Blowers, compressed air, air strippers

Water – Energy Nexus Disinfection

Chlorine (transporting/storing liability), Ultraviolet, Ozone

• UV Lamps

• Ozone generators

• Electric motors/dosing pump

Sludge Processing

Water – Energy Nexus Energy Distribution within a WWTP

Water – Energy Nexus

Water – Energy Nexus How to Optimize Energy

1. Installment of energy efficient measures

2. Adoption of improved processes

Local Government Requirement

Identify an energy baseline Implementation plan

Local government finance Project(s) realization

Continuous improvement through energy use monitoring

Water – Energy Nexus Energy Efficient Measures • Variable frequency drives (VFD): pumping, aeration • Automatic continuous DO control • Fine bubble diffusers for aeration systems • Retrofit hydraulic-driven systems with electrical drives • High efficiency pumps and blowers • Premium motors (above market quality) • Low-pressure UV disinfection system • Retrofit pneumatic pumps with electrical pumps • Air compressors with VFDs • Gravity belt thickening of sludge • Rotary and screw- type sludge dewatering • High efficiency lighting, HVAC

Water – Energy Nexus Improved Processes

• Anaerobic digestion in place of aerobic digestion

• Biogas utilization

• Biomass utilization

• Supervisory control and data acquisition (SCADA)

• Renewable Solar and wind energy

• Flow equalization demand and energy cost control

• Waste-to-energy

• Combined heat and power (CHP)

Water – Energy Nexus

Water – Energy Nexus

FINE BUBBLE AERATION

• One of the efficient aeration

technology used

• Increase oxygen transfer and treat-

ment efficiency than coarse bubble

• OTE 5 to 12 (lb O2/hp-hr)-Fine,

• OTE 2.0 to 3.0 (lb O2/hp-hr) -Coarse

• Reduces the energy usage/ costs

• Approximately 30% energy savings from coarse bubble

Water – Energy Nexus DISSOLVED OXYGEN CONTROL OF AERATION

• Maintain a DO concentration

that matches the demand of

of the biological activity

• Blowers or mechanical aerators operates on part-load

• Energy savings achieved 20% to 40%

Water – Energy Nexus VFD on Air Compressors

• VFDs save energy by varying motor speed

• 20 to 30% energy savings at part-load

• Tighter pressure control

• Longer motor life due to

built-in soft start mechanism

Water – Energy Nexus TURBO-BLOWERS

• Turbo blowers use advanced

bearing design (magnetic or airfoil)

to allow for very high impeller speeds (40,000 RPM)

• Units include integrated VFD,

DO sensor, and controls

• Enclosed, modular design

Water – Energy Nexus TURBO BLOWER ADVANTAGES

• 10-20% more efficient than conventional blower equipment

• Good turndown (to 50% capacity) with little efficiency drop-off

• Small footprint, lightweight

• Quiet, low vibration

• Very low maintenance requirements

Water – Energy Nexus

LOW-PRESSURE UV SYSTEMS • Low-pressure, low-intensity lamps are most efficient • Low-pressure UV lamps are recommended for small

systems • No chemical disinfection • Requires very little contact time (seconds versus minutes for chemical disinfection) • Use over 50% less energy than medium pressure lamps

Water – Energy Nexus

VARIABLE FREQUENCY DRIVES ON PUMPS AND BLOWERS

• Used in pumping and aeration

• VFDs save energy by reducing the speed of the pumps with the waste water demand

• VFDs reduce the speed (air flow) of the blowers to reduce the power draw of the blower motor

• Saves 70 % energy as compared to constant speed at 50% flow

• Soft start capability reduces wear and tear on motors

Case Study Aeration System Improvements – DO Controlled Blowers and Fine Bubble Diffusers Waco Metropolitan Area Regional Sewer System - Waco, Texas Facility Size: 37.8 mgd design, 22.8 mgd average daily flow

Description of Energy Conservation Measures (ECMs)

• The City of Waco, TX Utility Services Department implemented improvements to the aeration

system at their WMARSS WWF to address deficiencies in the plant’s nitrification process.

• Design air flow rate, producing coarse bubbles instead of fine bubbles, and the number of diffusers was inadequate.

• The aeration system improvements consisted of the following:

Supplementing the existing fine bubble membrane and ceramic disc diffusers with

additional diffusers. Number of diffusers in each basin was increased from 2,800 to 3,500.

Installing dissolved oxygen (DO) probes in each of the aeration basins’ three aeration

zones (mid‐way in the first and second aeration zones and at the end of the third

aeration zone).

Implementing automatic blower and aeration system control through the plant’s PLC

system using aeration basin DO readings. The plant’s control system software provided

the following

Electricity Use & Estimated Savings

Case Study San Jose/Santa Clara Water Pollution Control Plant, San Jose, CA Facility Size: 167 mgd design, 107 mgd average daily flow

Description of ECM Project Drivers & Issues

This case study describes several energy conservation measures (ECM) projects completed in 2008 which were partially funded by the California Wastewater Process Optimization Program (CalPOP).

The ECM projects implemented at the SJ/SC Plant consisted of the following:

• Pumping Systems Optimization

The first ECM project focused on reducing energy consumption by optimizing the

operation of three of the Plant’s major pump stations.

• BNR Process Improvements Pulse Aeration of Anaerobic/Anoxic Zones & Mixed Liquor Channels

A second ECM project implemented at the Plant involved switching the mode of air mixing

in the anoxic/anaerobic compartments of BNR plants from continuous to pulse (On/Off).

• Dissolved Air Floatation (DAF) Process Optimization

Optimization of the DAF process was achieved by reducing the energy used by the

pressurization pumps. This was made possible by utilizing proprietary algorithms developed by Ekster and Associates that provided the means to optimize the DAF control systems.

Estimated Savings Energy Use Before and After Pump Station Optimization

Energy Saved by Switching to Pulsed Aeration

Dissolved Air Flotation (DAF) Process Optimization

Case Study Advanced Aeration Control: Oxnard Wastewater Treatment Plant Facility Size: 31.7 mgd design, 22.4 mgd average

Case Study Advanced Aeration Control: Oxnard Wastewater Treatment Plant Facility Size: 31.7 mgd design, 22.4 mgd average The optimization/automation of the activated sludge system project includes: • Installing two on‐line TSS meters algorithms implemented as part of the

subject ECM. • Replacing outdated dissolved oxygen meters with optical sensor

technology • Installing software providing real‐time control of solids retention time

(SRT) • Replacing the Turblex blower pressure based control software with

DOmasterTM(Ekster and Associates Inc). DOmasterTM uses biological process model based algorithms instead of traditional PID algorithms for DO control

• Using OPTImasterTM (Ekster and Associates Inc) software to optimize set points for SRT and DO for each aeration compartment diffuser grid.

Description of Energy Conservation Measures (ECM)

Project Benefits are: • Energy: Average energy usage by blowers was reduced from 175

kW in 2002 to 140 kW in 2009. This resulted in a 306,600 kWh per year reduction or a 20% energy savings.

• Chemicals: Based on WWTP records: by reducing polymer dosage used for sludge thickening (benefit of improved sludge settleability), chemical costs were reduced by approximately $7,500 a year.

• Labor: Improved process monitoring and automation reduced the number of operator hours by at least one hour per day

• The total energy savings for this ECM are $26,980 per year. Including chemical cost savings and reduced manpower requirements, the total savings resulting from this ECM are $52,730 per year.

• Payback: is 5 years, if others savings included, will be 2.5 years

Case Study A new Aeration Control System at the Bird Island WWTP in Buffalo N.Y. Slashes Energy Costs • This project saves the city more than $350, 000/year

in energy cost • Aeration Control System for the plant’s 32 aeration basins,

replacing an older system • Improvement of aeration stability, handling fluctuation in

loads, and ability to use DO set points well below the norm, for additional savings

• M&V by NYSERDA – Review showed $357K annual savings. • Incentives offered by NYSERDA and National Grid • Project payback = 14 Months

Water – Energy Nexus References

1. CDP Water Disclosure 2010, Global Report

2. GAO, Energy Needed to Supply, Use and Treat Water

3. MWEA, WW Management Handbook

4. U of M, Energy Utilization: W&WWTFs report to MI H2O objective conference

5. WERF

6. Evaluation of Energy Conservation Measures, EPA

7. Water Utility Infrastructure (UIM)