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
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
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
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
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
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
47. For more information contact:
Dylan B. Thisse, P.E.
dylan.thisse@wright-
pierce.com
603.430.3728
Editor's Notes
Electrical energy is consumed by pumps, instrumentation, lights, vents, etc. There are very few operations, if any, at a plant that do not rely on electricity.
Largest users are pumps. In particular raw and finished water pumps.
Luckily there are many opportunities, in most cases, for conservation of energy.
While conservation and environmental efforts should start at the source, according to The U.S. Energy Information Administration, the bulk of our energy is still produced using fossil fuels.
Many times efficiency improvements in one section contribute to efficiency in other sections.
i.e. decreasing leakage in a system not only decreases distribution pumping, but also lowers the amount of treated water that needs to be produced, thereby decreasing runtimes for raw water pumps and treatment processes.
The stream we are talking about today is starred.
Many of todays lessons can be applied to other recycle streams as well as other parts of the treatment process.
National Primary Drinking Water Regulations (NPDWRs or primary standards) are legally enforceable standards that apply to public water systems. Primary standards protect public health by limiting the levels of contaminants in drinking water.
10 States Standards- Water and Wastewater design standards adopted by various states around the country. Many New England states reference these standards or have a slight variation on them. Covers things such as treatment process regulations all the way to hydrant spacing.
The total portion of inflow to a filter can have a maximum of 10% recycle water. So for a filter with an inflow of 1,000 gpm- 900 gpm can be raw water and 100 gpm can be recycle.
NHDES Requirements
Directly references CFR 40 sec 141.76- EPA National Primary Drinking Water Regulations
FBRR Objective
Reduce the concentration of Cryptosporidum oocysts in recycle water
Recycle streams are a POTENTIAL source of high concentration of microbial pathogens and chemical contaminants- basically all of the things you count on your filter and coagulant removing from the water are pushed back to the head of your plant by recycling filter backwash.
Contribute to the contaminant load
Coagulant chemistry imbalance
Hydraulic surge--overwhelms plant’s unit processes
Regulated waste streams
Spent Filter Backwash Water - A stream containing particles that are dislodged from
filter media when water is forced back through a filter (backwashed) to clean the filter.
Thickener Supernatant - A stream containing the decant from a sedimentation basin,
clarifier or other unit that is used to treat water, solids, or semi-solids from the primary
treatment processes.
Liquids From Dewatering Processes - A stream containing liquids generated from a
unit used to concentrate solids for disposal.
http://water.epa.gov/lawsregs/rulesregs/sdwa/filterbackwash.cfm
FBRR
Required for plants with ALL of the following
1.) Treating with Conventional or Direct Filtration
2.) Uses surface water or groundwater directly influenced by surface water
3.) Recycles filter backwash, etc.
FBRR
Requires the following
1.) Notify the state of your recycling practices
2.) Recycle directly to front of the plant
3.) Maintain Records- Records will vary by the design flow size of your plant.
Includes recycle flows, and frequency i.e. quantity
Filter run length
Type of treatment for recycle flows
Backwash flow rates and duration
Schematic, storage, and chemical treatment
Source: U.S. Energy Information Administration eia.gov
Permit Requirements
Zero or limited groundwater discharge permits essentially require plants to have recycle streams.
Reduced Waste Disposal Costs
Recycling filter backwash water reduces need for storage and disposal as well as size of those facilities.
Water Conservation
Simple- Recycling water that would be going to waste conserves a large amount of source water
While there is a potential presence of microbial contaminants in filter backwash water, the decant is often cleaner than the raw water entering the filters.
Energy Savings
A large portion of energy costs are from raw water pumps. Recycle pumps are typically much smaller than raw water pumps. Recycling Reduces the amount of raw water that needs to be pumped and can lead to savings, especially if raw water pumps are set on VFD’s. An overall reduced flow will be reduce required pump speeds and run times, which a VFD can account for while a throttling valve and a motor set to run at full speed will not.
Chemical doses were assumed for PACL, HCL, etc. No unique treatment chemicals.
Separation of water from solids can be obtained by and equalization and sedimentation chamber, mechanical dewatering, etc.
New Hampshire State Energy Profile $12.33/kWH US energy information administration
The majority of costs are due to disposal cost.
Additional Chemical Costs are to treat 25,000 gallons of water per day- Actually a wash- you would be treating raw water with this either way
Only additional pumping cost is for recycle pumping because the same amount of water is processed through the plant as would be if all recycle was sent to waste.
Backwash pump is a partial trade off with a wasting pump. HP is typically greater on recycle pumps
Backwash pumping reduces raw water pumping.
12.33 cents taken from the US energy information administration- Average industrial power cost for NH
Sewer Rate is taken from Dover NH as a residential rate. Rate for municipal plant may be lower, but the cost of treatment is still real.
Payback only takes into account select energy savings and reduced disposal costs.
Other benefits include water conservation, reduced raw water pumping, etc.
It can be seen that while recycle has a potential for large savings, capital costs for storage, pumps, instrumentation, VFD’s, etc. still have a substantial payback period. Increasing efficiency will lower this time period.
Does not take into account inflation.
The overall result is that backwashing is beneficial from an energy and cost perspective on a case by case basis. On a cost basis it might not always be beneficial to a plant to recycle their filter backwash, but usually it makes sense for other reasons i.e. water conservation and storage or disposal issues.
Filter waste went directly to sewer.
Started using backwash recycle
Generic, will vary by system
Backwash pumps usually run for short durations.
Emphasis on demand charges- essentially the ability to instantly supply a large amount of energy. Reducing your large occasional energy demands, such as at pump start up, can reduce these charges.
Demand charges vary based on peak hours. Talked about later in presentation.
Optimizing chemical addition will reduce the quantity of sludge- most filter waste sludge is alum floc
Remember that when recycling additional chemical may be needed depending on your waste stream
Minimizing backwash duration will reduce the quantity seen. Can be improved through air scour, varying pump rates and durations.
SCADA may be able to allow for production during off peak hours.
Most facilities consist of pumping and piping systems in one form or another.
Less backwash equals less flow
More recycle reduces flow through raw water pumps
Promoting Conservation Reduces Demand
1.) During design or retrofit a pump can be sized so that under normal operating conditions the BEP is achieved.
2.) properly size both the pump and the motor. cycling of motors reduces the wear and maintenance on individual pumps. It also increases redundancy in the system.
3.) high efficiency motors can greatly reduce energy consumption.
4.) If a motor is running under a hard start, for a short duration, at an inefficient point on its curve, and this is not necessary, the pump can be modified using programming and VFD’s
5.) Regular maintenance keeps pumps running smoothly and reduces heat and friction.
6.) Automated controls can be set to limit speed, reduce heat, SCADA
TDH- total dynamic head taking into account height pumped and friction losses.
If a pump curve can be determined for the existing pump, that curve can then be compared to the manufacturers original to determine if pump is performing efficiently. If not the pump may require maintenance, rebuilding, or replacement.
Make sure you are matching up the correct pump with the correct curve
Make sure that any impeller trimming is recorded for pump evaluation
The greater the efficiency the less energy required
Horse power curves
NPSH- Minimum amount of pressure on the suction side of the pump to overcome pump entrance losses. Pump will cavitate without proper NPSH.
Operating range for all factors combined
Minimizing backwash duration minimizes quantity
Optimum filter backwash turbidity will vary by system
Filter ripening time should be minimized when filter is placed back online
filter backwash recycle goes through the entire treatment process again, so raw water can be used. Depends on raw water quality and may require some filter to waste.
The use of air scour in the backwash process may allow a reduction in the backwash rate and duration, producing less spent filter backwash.
Backwash based on head loss or differential pressure rather than time.
Increasing filter run times can decrease the number of backwashes needed.
Optimizing chemical addition can also increase filter run times. Mostly alum sludge in waste.
Avoid running filter to point of breakthrough
BEP= BEST EFFICINCY POINT
Throttling valves burns up a portion of the energy expended by the pump.
The better alternative is VFD’s- allow for efficient operation of a pump at a range of outputs.
Instrumentation and controls allows the user to set parameters from a SCADA control screen. I.E. flow meters, level controls, etc. Allows for greater control and programming.
Continuous operation simply uses energy. If pumps must remain running VFD’s can be used to minimize required energy.
Frequency and voltage control the speed of a pump. Varying these can speed up or slow down a pump.
Rebates through larger utilities like national grid or eversource. Rebates may still be available through a local electric utility though.
Some municipalities qualify for grants under rural development. Just as with most rural development funding, specific criteria must be met as to average household income, population size, etc.
Tax incentives may be available as part of larger efficiency programs such as LEED certifications or renewable energy projects
Participation in energy demand markets requires cooperation between the local utility and the user. It requires a very through evaluation and monitoring program. We have never personally had a project use this incentive, but if a project was large enough, say an entire treatment plant or distribution center. It may be worth evaluating this.
Who has SCADA?
Preventive and predictive maintenance are central to having energy efficient equipment.
Operating equipment should be inspected daily. Touch, listen, look, smell.
Lubricate according to manufacturer’s recommendations. Use oil analysis.
Check amperage/voltage unbalance and primary insulation.
Check pump performance, wear surface clearance, etc. If a pump requires a lot of maintenance or performs poorly another type of pump may be more appropriate.
IR Thermometers and thermography shows heat buildup that will eventually result in a breakdown.
Vibration analysis can be used to identify worn bearings, misalignment, loose anchor bolts, and other problems.
There are other evaluation tasks that could be performed. However, this list will eliminate 98% of the surprises.
Recommended Annually
From the US Deparment of Energy
Lots of great resources for energy assessment
The PSAT tool can be used to compare current pump efficiency with that of a replacement pump. Actually believe there is a quantification part of the tool.
It can also be used to define minimum VFD set points for efficient operation points.
Several different ways to dispose of backwash filter waste. Many can be combined with recycling techniques.
Prohibited Discharges
The discharge of ANY wastewater containing a regulated contaminant is prohibited as detailed in the
Ambient Groundwater Quality Standards under EnvWq
402. These prohibited discharges include:
· Facility discharges from open floor drains where regulated contaminants are used or stored.
· Backwash from activated carbon treatment systems for the removal of chlorinated compounds,
volatile organic compounds, or other petroleum and
Solvent related
contaminants.
· Unfiltered or unsettled backwash from arsenic treatment devices.
Greensand filter removing iron and manganese from ground water source. Recharged with potassium permanganate to recharge filter. Backwash water stored in two tanks and allowed to settle. Dolphin pump used to siphon clean decant from top and sent to front of plant. Remaining sludge pumped into secondary tank and stored. Remaining sludge often settles again and is mostly water. No reliable way to siphon this water to recycle safely without compromising filter.
Installing two infiltration lagoons will allow for the operators to use an external pump to discharge this remaining water to the infiltration lagoons. Resulting in a concentrated sludge and reduced removal quantities and costs.
Backwash flexibility is increased in the ability of the infiltration basins to take a portion of the backwash intended for recycle if necessary. Currently no piping directly into the tanks is intended, but this could be modified in the future for ease of use. The size of the lagoons is limited due to space constraints and cannot accept full backwash quantity.
Environmental permitting was required and water quality was tested. Relates to filter backwash rule, if levels of contaminants were too great then water would need to be hauled off or reprocessed.
Equalization chambers are essentially storage chambers that can be used to decrease settling times and normalize the flow of recycle into the raw water stream.
Minimizing instrumentation dead band by recessing ultrasonic level instrumentation. Choosing the right instrumentation for the application (spacing from walls, age of control system, etc.)
Installing updated flow meters for accurate readings at the proper distances up and down stream. Improving as technology improves.
Creative programming includes limits on variables such as current, electrical draw, etc.
Decreasing settling time using baffle curtains and walls
Enchanced sludge removal using track vacs, chain and flight systems, as well as timing backwash pumps to remove waste as flow is introduced into equalization chamber.
BEFORE
Plant runs off of two different surface water sources seasonally. One close by and the other pumped using raw water pumps with soft starts. Pressure is much greater from the second source.
Plant originally had limited backwash filter capacity
Waste pumps pumped 24/7 when necessary directly to the sewer in order to create space in the tanks
Recycle was limited due to pump size and required pressure to overcome the second raw water source pumps. Essentially no recycle was possible during this time.
Waste and Recycle pumps were connected to SCADA and regulated by over the pipe flow meters.
AFTER
Upgrading recycle pumps allowed for year round recycling
Increased storage allows for ability to recycle stored capacity within set limits
Decreased settling time using baffle wall.
Improved instrumentation and VFD’s allow for the pumps to be efficiently operated and accurately monitored for flow.
Timer function programming is yet to be implemented, but should decrease the amount being wasted and increase the amount being recycled.
Timer function was to be used to allow for greatest amount of clean recycle to be present in the equalization chamber while still creating room for next wash.
Complicated system that uses both level and time controls.
Timer functions can be used to separate pumps from the level instrumentation. Requires some calculation and should be combined with a redundant back up to reduce risk of overflow or over pumping.
SCADA can provide much of this data if properly recording
Pump efficiency is the number one way to improve energy efficiency
Reducing quantity needed for filter backwash will improve