This document discusses opportunities for improving plant efficiency through optimizing recycle processes and backwashing operations at water treatment facilities. It notes that recycle optimization can reduce energy usage, waste disposal costs, and promote water conservation. Specific opportunities discussed include minimizing backwash quantity, recycling backwash water, promoting conservation, improving pump efficiency, optimizing filter backwashing, improving sludge collection, and properly designing system upgrades. Undertaking energy audits, installing variable frequency drives, and maximizing recycle quantities while minimizing waste are presented as ways to realize these efficiency improvements.

1. GWSRA 2015
Presented by:
Dylan B. Thisse, PE
Improving Plant Efficiency
Through Recycle Optimization

2. • Recycle process and regulations
• Why recycle filter backwash water?
• Optimization of backwashing
• Optimization of recycle and filter waste disposal
• Water treatment facilities upgrade considerations

3. • Water facilities consume large amounts
of electrical energy
• Raw and finished water
pumping average:
1,500 KW-hour/MG
• Many opportunities for conservation
• Note: 67% of electrical energy is produced
using fossil fuels

4. Distribution
Pumping
67%
Treatment
Process
11%
Raw Water
Pumping
11%
Lighting &
Buildings
2%
In-plant
pumping
9%
87%

6. • National Primary Drinking Water Regulations
• EPA Filter Backwash Recycle Rule- FBRR
 Cryptosporidium control
• 10 states standards
 Max 10% inflow
• NHDES Requirements
 Env-DW 716- Filtration, Disinfection, and Waste
Recycling
 Direct reference to NPDWR standards

7. • EPA Filter Backwash Recycle Rule- FBRR
 Cryptosporidium control
• For plants with ALL of the following
 Treating with conventional or direct filtration
 Surface or groundwater under influence of surface water
 Recycling filter backwash
• Requires
 Notifying state of practices
 Recycle to front of plant
 Maintain records- flows, frequency, quantity
• Great Resource
http://water.epa.gov/lawsregs/rulesregs/sdwa/filterbackwash.c
fm
7

8. • Permit requirements
• Reduced waste disposal costs
• Water conservation
• Energy savings

9. • Conventional plant
• Assume 1 MGD
 Recycle sent to the front of the plant
 All chemicals re-applied at raw water doses
 95:5 % separation H2O to solids
 25,000 gallon BW for analysis
 Assume 2 units
 1 backwash each, every other day= 365 backwashes
per year.

10. • Sending all filter backwash to sewer
 =$7.52 / 748 gallons or 1 unit
 9,125,000 gallons
 12,199 units=$91,738 per year
• Pumping to waste
 19,597 kWH/yr (3HP, 365 days, 24 hrs/day)
 At 12.33 cents/kWH= $2,416
• Total cost
 $91,738+$2,416=
 $94,154 per year- cost of wasting

11. • 9,125,000 gallons of backwash
• 8,668,750 gallons of effective recycle
• 456,250 gallons of residuals
• Additional chemical costs- $2,000 per yr
• Additional power usage-
 For recycle pumping
 18,780 kWH/ year (3HP, 365 days, 23hrs/day)
 At 12.33 cents/kWH= $2,316

12. • Disposal of sludge to sewer
 =$7.52 / 748 gallons or 1 unit
 610 units=$4,587
 Pumping to waste-
 817 kWH/yr (3HP, 365 days, 1 hr/day)
 At 12.33 cents/kWH= $101 per year
• Total operating costs for recycle
 $2,000+$2,316+$4,587+$101
 =$7,004 per year- cost of recycling

13. • $94,154 - $7,004= $87,150 per year
• Straight line payback on $1,000,000 capital cost
project= 12 years
• Capital and maintenance costs
• Conservation benefits
• Reduced wastewater burden

14. • Storage Capacity and Equipment
• Operations and Maintenance
 Pumps and piping
 Instrumentation
 Monitoring and recording
 Operator effort
• Benefit or Burden?
 Case by case

15. • Opportunity
 water plant had 10% filter waste
• Enhancements
 employed backwash
water recycle system
• Results
 reduced filter waste to 2%
 reduced raw water pumping energy by 8%
 reduced sewer bill by 80%

16. • Backwashing of filters consumes little energy
• Backwash pumps are significant contributors to
demand charges
• Modify procedures to operate backwash pumps
during off-peak hours- load shifting
• Variable frequency drives
• Optimize chemical addition
• Optimize backwash process

17. • Increase water production during off-peak hours
to reduce water treatment/pumping during on-
peak hours
• Depends on available water storage and
flexibility of staff to operate during off-peak hours

18. • Pumps consume the
majority of electrical
energy at water
facilities
• Biggest opportunity
for energy savings

19. HP=Q(ɤ)H/246,840(e)
= Q(H)/3956(e)
HP=horsepower input
• Q=flow, gpm
• ɤ=specific wt of water,
62.4 1bs/cf
• H=head, ft
• 246,840=conversion factor
• e=combined efficiency of pump, drive and motor

20. E=(HP)T(.7457)
• E=energy consumed, kWH
• HP=horsepower input
• T=operating time, hrs
• .7457=conversion factor,
kW/HP
E=QH(T)/5305(e)

21. • Reduce flow, Q
• Reduce head, H
• Reduce pumping time, T
• Increase pumping efficiency, e
E=QH(T)/5305(e)

22. 1. Reduce backwash quantity
2. Recycle backwash water
3. Promote conservation
E=QH(T)/5305(e)

23. 1. Select most efficient pumps
2. Proper size and number of Pumps
3. Select most efficient drives and motors
4. Operate in most efficient manner
5. Regular maintenance
6. Rebuild/upgrade worn equipment
7. Automated controls and monitoring
E=QH(T)/5305(e)
e= (pump eff)x(motor eff)x(drive eff)

24. • Pump testing can identify
where a pump operates
on its performance curve
• Measure flow and TDH
to determine pump curve
operating point

25. What is on a pump curve diagram?
• pump I.D. (model #, RPM, etc.)
• pumping rate vs. total
head (per impeller)
• efficiency curves
• horse power curves
• net positive suction head
requirements
• operating range

26. • Opportunity
 Replace end suction
centrifugal pump with vertical
turbine pump
• Enhancements
 Increase pump efficiency from
38% to 84%
• Results
 Yearly cost savings: >$4,100
 Obtained energy efficiency
grant for VFDs, motors

27. • Common to gain 2-3 % pts
• Replacing old motors
typically has a very short
payback (2-3 years)
• Payback affected by motor
size, energy rates and hour
per year of operation

28. • Minimize backwash duration
• Use air scour
• Increase filter run times
• Backwash based on head loss or differential
pressure
• Modify procedures to operate backwash
pumps with raw water and finish water pumps
off
• CAREFULLY monitor changes
 Increased turbidity
28

29. 1. Operate close to BEP
2. Avoid throttling valves
3. Use VFD’s with variable
demand
4. Use instrumentation
systems for control
5. Avoid continuous operation
independent of demand

30. • Vary frequency and voltage to minimize electric
load for required pump speed
• Combine with flow meters
• Efficient- just enough energy
• May be used to eliminate throttling valves
• Softer pump start up and shut down
• Reduce water hammer
• Grants, rebates, loans, and tax incentives

31. • Rebates
 Through local utility
• Grants and Loans
 USDA-rural development
• Tax Incentives
 Part of larger energy efficiency program
• Participation in Energy Demand Markets
 Complicated and costly for small projects

32. • Resources
 NHSAVES program- www.nhsaves.com
 Database of State Incentives for Renewables and
Energy- www.DSIREusa.org
 Department of Energy www.energy.gov
 Energy Markets- www.iso-ne.com
Contact Agencies even if NO programs are
listed.

33. • Effective tools for managing energy usage
• Monitor pump efficiencies
• Control the system to optimize efficiency
• Load shift or shed
• Control the speed or pressure on
speed variable pumps
• Alarm when electrical demand in kW
exceeds predetermined targets
• Vibration monitoring
• Heat monitoring

34. • Collect operating data
• Confirm pump performance
• Frequent equipment inspection
• Correct lubrication
• Electrical condition of motors
• Thermography
• Vibration analysis
• Replace worn equipment

35. • Pump testing can help identify if a pump is still
operating at expected efficiency and where on
its performance curve it is operating
• By measuring flow and the differential head
across a pump and comparing with the
manufacturer’s pump curve

36. • Pump efficiency
 flow meters & pressure taps
• Pumping System Assessment
Tool (PSAT) program
(www.eere.energy.gov/Industry)
• VFD minimum set points

37. • Direct to Sewer
 Distribution pumping and maintenance
 Added load at wastewater plant
 $$$ Disposal costs
• Drying Beds and Infiltration Lagoons
 Typically low comparative capital cost
 Effluent content dependent
 Requires space and maintenance
 Size properly

38. • Storage and Removal
 Waste tank or lagoon
 Trucking sludge
 Limited space
 Higher capital and disposal costs
• Back to the Environment
 Specific permit requirements
 Dependent on contaminants
 Rarely if ever done

39. • Opportunity
 Minimize sludge quantity
 Increase backwash flexibility
 Partial recharge of aquifer
• Enhancements
 Two 25’x25’ unlined infiltration lagoons
 Obtained environmental approval for discharge
• Results
 Installation anticipated 2016

40. • Equalization chambers
• Improved instrumentation
• Efficient motors and pumps
• VFD’s
• Timer functions/ creative programming
• Floating decant intakes
• Decreasing settling times
• Enhanced sludge removal systems

41. • Opportunity
 Increase ability to recycle
 Reduce quantity wasted
• Enhancements
 New pumps, motors, and VFD’s
 Improved storage capacity/equalization chamber
 Improved controls and instrumentation
 Timer functions and creative programming
 Maximize quantity of available clean recycle
• Results
 Increased recycle quantity and decreased wasting quantity
 Still testing programming
 Further optimization available

42. • Water tank mixing
• Power management
• HVAC equipment
 heat recovery
• Building envelope
• Lighting systems
• Solar

43. • Do an energy audit to quantify
energy used by equipment
systems and identify
opportunities to conserve
• Audits can be performed
in-house, contracted, or
sometimes by the power
supplier.

44. • Billing and rates (demand charges)
• Energy use patterns
• Detailed equipment list
• Run times
• Pressure/flow measurements
• kW, PF, amp draw
• Justify energy bills through equipment inventory and data collection
• Document current usage
• Identify low cost operational adjustments
• Payback analysis on equipment replacement
• Instrumentation for monitoring and control
• Energy and fuel supply modifications

45. • Extension of the walk
through audit
• comprehensive
identification
• analysis of energy
conservation measures

46. • Increase pump efficiency
 Process audits, efficient motors,
VFD’s, SCADA
• Minimize/Optimize Filter
Backwashing
• Improve Sludge Collection
• Properly Design Upgrades
 Size, No. of pumps, Settling time
• Promote Conservation

47. For more information contact:
Dylan B. Thisse, P.E.
dylan.thisse@wright-
pierce.com
603.430.3728