Metropolitan Wastewater Treatment Plant
St. Paul, Minnesota
All plants have an obligation to ratepayers to deliver the best wastewater treatment service at the lowest cost. As polymer prices started to soar even faster than energy costs, plants have needed to find new ways to reduce its dewatering polymer use. Some improvements are capital intensive, such as installing newer equipment. Others cost very little; they are simply improving the way we do things, such as putting the operators in charge. Most plants change operating goals passed down to operators intermittently as specific directives: “Try not to use more than 15 GPM of polymer, and keep the cake at least 27%.” This sort of instruction is OK, but usually not done often enough to account for changes in the dewatering processes. In the Minneapolis-St Paul Metro Plant the control system displays, operators are empowered to make changes independently, hour by hour, so the dewatering costs can be constantly minimized. We are looking into on line analyzers, to continuously monitor the blend ratio. The instruments for continuous solids measurement were unreliable ten years ago, but are now proven. Since polymer has now surpassed electricity as the largest expendable for solids processing (Table 1), another enhancement will be to combine energy and polymer costs on a real-time solids management screen. This would be incorporated into the already developed energy cost/conservation screen (Figure 8). MCES is also investigating ways to reduce the sludge yield in the winter (when most of the secondary sludge is produced). A 25 dryton-per-day reduction of secondary sludge production could save $400,000 in polymer while costing $200,000 in extra energy netting a savings of about $200,000 per year. Source: WEFTEC 2008 Proceedings
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Posted: August 27th, 2010 | Filed under: >1M, Waste Water Treatment | Tags: Cost Savings, Improved Organization, Plant Optimization | No Comments »
San Jose/Santa Clara Water Pollution Control Plant
San Jose, California
The San Jose/Santa Clara Water Pollution Control Plant (“Plant”) is an advanced wastewater treatment facility with a rated capacity of 167 MGD. Over the past year it implemented three major energy savings projects: optimization of pump station operation, optimization of operation of the dissolved air floatation system and replacing continuous aeration of mixed liquor channels and anaerobic/ anoxic compartments of the BNR process with pulsed (intermittent) aeration (Patent pending). Estimated energy savings is $1.3 million dollars. Cost of the projects was less than $300,000. Project cost was refunded to the Plant by the Electrical Utility. The following results were achieved: 1. More than 20% energy savings was achieved by optimization of scheduling of pumps and speeds of VFD motors.
2. More than 60% energy saving was achieved by optimization of operation of dissolved air floatation.
3. More than 50% energy savings was achieved by implementing pulsed aeration in the anaerobic compartments.
4. No deterioration of treatment performance was observed. Source: WEFTEC 2009 Proceedings
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Posted: August 27th, 2010 | Filed under: >1M, Waste Water Treatment | Tags: Cost Savings, Energy Savings, Plant Optimization | No Comments »
Orange County Sanitation District
Orange County, California
The Orange County Sanitation District (OCSD) solid production is projected to exceed the plant dewatering capacity in the next few years. OCSD must increase the capacity of its belt filter presses (BFPs) to each treat 140 gpm to meet future handling requirements. To optimize the BFP, an operator-center approach is integrated into the process. A testing protocol was created to study the BFP system with: no changes, belt replacement, belt washing modifications, different polymer types, and a new polymer makedown unit. The test protocol was altered by the operator during testing to maximize the cake solids concentration. With 500 scfm belts installed, it was possible to obtain 20% solids (19.84%) at 140 gpm. However, it was not possible to achieve greater than 20% solids using mannich polymer with the tested makedown unit. Alternatively, emulsion polymer required 24 lbs/dry ton of polymer to achieve 21% solids. The results indicate that the optimization program achieved 140 gpm of influent sludge feed and produced 20% DS dewatered cake. A full description of the methodology and the test procedure is supported by the operating conditions, capture efficiency, and dryness of the dewatered cake for each test phase. The paper is relevant because it provides BFP operators with a demonstrated method for improving dewatering capacity and quantifying and documenting results without having to install additional capital facilities. The investigation also illustrates the importance of the interaction between engineers and operators to arrive at solutions that are acceptable to both groups of people. Source: WEFTEC 2009 Proceedings
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Posted: August 27th, 2010 | Filed under: >1M, Waste Water Treatment, Water Treatment | Tags: Cost Savings, Extended Useful Life of Equipment, Improved Plant Efficiency, Optimized Belt Filter Press Dewatering | No Comments »
Metropolitan Water Reclamation District of Greater Chicago
Chicago, Illinois
The District’s mission includes the protection of our water environment, specifically the water
quality of Lake Michigan, the region’s drinking water source, at all times in compliance with our
NPDES permits. All of the energy management measures listed above were implemented
without compromising or diminishing our ability to meet our primary goal. As an environmental
organization, the District has a responsibility to not only to achieve its primary function of
treating wastewater, but also to do so in an environmentally responsible manner.
The measures discussed above ultimately result not only in O&M cost savings but energy use
reduction. The decrease in energy use reduces the emissions of greenhouse gases, which has
taken on a new significance with the current concern regarding global warming and its predicted
dire effects on the planet and its ecosystems. They also demonstrate how vigilant maintenance of
public systems can have benefits above and beyond the immediate results.
The success of any initiative is directly dependent on the knowledge, dedication and efforts of
personnel involved not only in establishing protocol, but also in implementing and performing
the associated tasks on the daily basis. The District’s success, as measured by the cost savings
and energy reduction shown in the tables above, demonstrates the ability of District personnel to
work collaboratively as a team. The District will continue to seek additional measures to be
implemented at all facilities to not only save taxpayer money but also to operate more efficiently
to better improve the overall environment.
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Posted: August 24th, 2010 | Filed under: >1M, Sanitary Sewer, Waste Water Treatment, Water Treatment | Tags: Energy Savings, Environmental Impact, Improved Plant Sustainability, O&M Cost Savings, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Santa Clara Valley Water District
San Jose, California
The Santa Clara Valley Water District (District), the primary water agency for Santa Clara
County, which encompasses the southern part of the San Francisco Bay, provides water supplies
for an expanding urban population containing 1.8 million resident, hosting 200,000 commuters,
and harboring Silicon Valley, a major economic driver for California.
To help meet increasing water demands, the District has developed a comprehensive suite of water
conservation and water recycling programs that have resulted in cumulative savings of 427,000
acre-feet (AF) of new water supplies between fiscal year (FY) 92-93 and FY 06-07. In addition to
saving water, water conservation and water recycling programs save energy and reduce air
pollutant emissions due to the significant quantities of energy required (and air pollutants
generated by energy production) for the water supply chain: 1) Water conveyance; 2) Water
treatment; 3) Distribution; 4) End use; and 5) Wastewater treatment.
Air pollutants generated include (depending on energy source) the following: reactive organic
gases, sulfur oxides, nitrogen oxides, particulate matter, and carbon dioxide. The latter is a greenhouse
gas that contributes to global warming.
The climate changes and other impacts that occur as a result of global warming present challenges
for water agencies. Sea level rise (including saltwater intrusion into the freshwater San Francisco
Bay-San Joaquin Delta levee system), a decrease in snow pack in the Sierra Nevada mountain
range (which supplies water for much of the state), and increased drought are all possible outcomes
of global climate change. The District is committed to responding to these challenges through
adaptation (preparing for future changes) and mitigation (reducing the District’s role in global
warming through more efficient use of resources).
With regard to the mitigation of global climate change, the District recently completed an analysis
of the energy saved by its water conservation and water recycling programs, which have been in
operation since FY 92-93. For FY 92-93 through FY 06-07, the District has saved approximately 1.62
billion kilowatt-hours (kWh) of energy, which represents a financial savings of approximately $208
million and is equivalent to the annual electricity required for 236,000 households. Through saving
energy, the emissions of approximately 381 million kg of carbon dioxide, a greenhouse gas, were
eliminated, which is the equivalent of removing 82,000 passenger cars from the roads for one year.
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Posted: August 24th, 2010 | Filed under: >1M, Waste Water Treatment, Water Treatment | Tags: Cost Savings, Energy Savings, Increased Plant Efficiency, Reduced Air Pollutants, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions, Water Conservation, Water Recycling | No Comments »
San Jose/Santa Clara Water Pollution Control Plant
San Jose, California
Results showed no serious effluent quality deterioration when continuously air-mixed anaerobic and anoxic quadrants of the San Jose/ Santa Clara Water Pollution plant’s secondary aeration systems were operated in pulse aeration mode. Ammonia concentrations in pulse aerated and continuously aerated tanks were, on average, 0.73 mg/l and 0.63 mg/l, respectively. Such a slight increase in ammonia concentration in pulse aerated tanks was inevitable with reduction in air flow to Quad 3, although the final effluent quality was never affected. Nitrite concentrations were on average 0.15 mg/l and 0.17 mg/l in the pulse aerated and non pulsed tanks, respectively. Nitrate was significantly reduced from an average concentration of 7.26 mg/l in continuously aerated tanks to 4.45 mg/l in the pulse aerated tanks. Phosphate levels in the effluents of pulse aerated experimental tanks were found to be higher than those in continuously aerated control tanks with averages of 2 mg/l and 1.5 mg/l, respectively. No significant difference was observed in mixed liquor suspended solids concentrations between pulse aerated and continuously aerated tanks, signifying that the chosen pulse aeration cycle of 1.5 min ON/10.5 min OFF was, indeed, sufficient to keep solids in suspension. Tanks with pulse aerated anaerobic and anoxic compartments produced final effluent as superior in quality to the NPDES permit requirements as those that were not pulse aerated. The study demonstrated implementation of pulse aeration in anaerobic and anoxic quadrants would result in 13% less total aeration demand with associated annual energy saving potential close to $430,000. Source: WEFTEC 2009 Proceedings
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Posted: July 6th, 2010 | Filed under: >1M, Waste Water Treatment | Tags: Cost Savings, Energy Savings, Reduced Nitrate Concentrations | No Comments »
Eastern Treatment Plant
Bangholme, Victoria (Australia)
Use of ozone followed by biological media filtration has been shown in this comprehensive pilot and demonstration scale test to enhance secondary effluent for reclamation purposes. Some enhancements are desirable simply because of better public acceptance, including significant color reduction, and micro-contaminant reduction. However other enhancements like turbidity removal, additional disinfection and ammonia reduction improve effluent from a compliance perspective. Other technologies were trialed including membrane ultrafiltration and reverse osmosis. The ozone BMF treatment platform also improved downstream membrane filtration processes by significantly increasing stable filtration flux and extending “clean-in-place” intervals. The technology increased 5%ile UV transmissivity values from 34% to almost 60%, resulting in significant cost savings in UV disinfection equipment requirements. Lastly, preliminary results indicate ozone increases average BMF solids removal capacity by 46%. “This process delivers the best value for money now and into the future, as a platform for providing flexibility to further enhance recycled water treatment, as needed” (Melbourne Water, July 2009). Source: WEFTEC 2009 Proceedings
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Posted: July 6th, 2010 | Filed under: >1M, Waste Water Treatment | Tags: Ammonia Reduction, Cost Savings, Improved Effluent, Increased Solids Removal, Innovative Technology | No Comments »