DynaSand EcoWash Intermittent Backwash Filter - Pompano Beach, FL
Continuously backwashing sand filters are limited by high volume of backwash water and unoptimized filter performance. Using a methodical experiment protocol spanning June-August, 2010, at the City of Pompano Beach Reuse Utilities Plant, the DynaSand® EcoWash™ Filter was compared against standard design continuous backwash sand filters.
Using two identical DynaSand® cells, one cell was converted to a DynaSand EcoWash Filter while the other cell was left in its standard setup. Sampling equipment and some modifications were installed in both cells to ensure equal conditions in order to compare relative performance.
The DynaSand® EcoWash™ Filter cell was tested with several programmed and time-controlled backwash scenarios to reduce reject/backwash production while maintaining effluent quality within guidelines. Meanwhile, the Standard Operation filter cell was tested normally with continuous backwash. All data was logged via PLC in the Control Panel and daily samples were taken and analyzed in the lab for turbidity and total suspended solids. Over the three month full scale test, the results showed a 90-95% reduction in backwash production and energy use, coupled with a 15-25% average improvement in filtrate quality.
Further testing will continue for the purposes of scientific investigation and continued data collection. We can expect to continue testing a variety of time controlled and differential pressure controlled backwash scenarios to optimize the system even further.
Throughout the past three decades, DynaSand® continuous backwashing filter has been successfully applied to thousands of installations, providing quality filtrate while offering minimal operator attention and maintenance requirements. A major perception in the industry is that continuous filters like the DynaSand® Filter produce significantly more total reject (backwash) than intermittent backwashing filters. Customers desire better quality to meet legislative and effluent requirements while minimizing total reject. The cost of reprocessing excess reject is a major concern as well.
This product has been developed to – Reduce reject/ backwash rate – Reduce operation and maintenance costs – Improve energy efficiency – Improve filtrate quality
The DynaSand® EcoWash™ Filter allows continuous operation while utilizing time programmable or head loss controlled sand circulation and washing to reduce the amount of backwash water being produced.
The full scale testing of the DynaSand® EcoWash™ Filter was performed at the City of Pompano Beach Reuse Water Utilities, Pompano Beach, FL. The Pompano Reuse Plant is an 8.64 MGD maximum capacity tertiary filtration (DynaSand® Filter) plant. The influent passes through a bar screen and a gate valve directs the flow to each filter. Influent turbidity ranges between 3 and 6 NTU and is drawn from the Broward County North Regional WWTP effluent discharge to the ocean. The plant currently has two separate DynaSand® Filters: the North Filter and the South Filter. The North filters consists of 4 cells with 2 standard bed filters per cell, while the South filters consists of 2 cells with 8 deep bed filters per cell. The test was conducted on the first two cells of the North Filter.
During the testing, Cell 1 was utilized for testing the DynaSand® EcoWash™ Filter and Cell 2 was utilized as a Standard Operation cell for comparative data collection purpose. A side by side comparison of test parameters was possible in this configuration. Refer to Figure 1 for the layout of test components.
The following modifications were installed in each cell to ensure equal conditions and for comparative data collection: – Influent channel weir boxes to ensure equal flow – Inline turbidity meters for measuring influent and effluent conditions – Sensors to measure influent, reject, and effluent flow rates – Differential Pressure Monitoring
The following components were installed only in Cell 1 as part of the features of the DynaSand® EcoWash™ Filter: – Sand Movement Verification System – Differential Pressure Monitor – Cell Air Control Panel – Central Control Panel with PLC and HMI Screen – Reject Water Reduction Control Valve – Redesigned Airlift
As such, turbidity, flow, and head loss were constantly monitored through in-line instrumentation and the HMI screen. Any spikes in turbidity were closely watched throughout the test duration. Daily samples of effluent were taken from both the DynaSand® EcoWash™ Filter cell and the Standard Operation Filter cell. The samples were analyzed at the City of Pompano Beach reuse facility laboratory using its established procedures for turbidity and TSS. The effluent from Cells 1 and 2 were then allowed to combine with the effluent from the South Filters and flow to a chlorine contact chamber where it would then be sent to the City of Pompano Beach as irrigation and reuse water.
|Reject Analysis - Table 1|
|DynaSand® EcoWash™ Filter||Standard Operation Filter|
|Total Backwash Time||30 Minutes/Cycle||300 Minutes/Cycle|
|Total Reject Flow||384 Gallons/Cycle||3600 Gallons/Cycle|
Table 1 demonstrates that backwash time directly determines the total amount of backwash rejected. At an average rate of 12 gpm, the standard filter in constant backwash produced 3600 gallons of backwash per cycle. The DynaSand® EcoWash™ Filter backwashing only 30 minutes produced 384 gallons of backwash water during the same time period. This 90% reduction in backwash time corresponds with about 90% reduction in backwash volume.
The test results speak to the DynaSand® EcoWash™ Filter’s proven performance in full scale installations by demonstrating reliable operation with significantly reduced backwash production and energy expenditures without suffering in effluent quality. Through this full scale test at the City of Pompano Beach Reuse Utilities, the DynaSand® EcoWash™ Filter has shown to drastically reduce backwash and energy consumption, while increasing overall filtrate quality and capacity.
This table gives the annual reject water production for a typical 16 Filter (50 SqFt) – 5.76 MGD capacity facility with standard sand filters as compared to the DynaSand® EcoWash™ Filter.
The DynaSand EcoWash Filter will consistently produce higher quality effluent on average despite slight spikes in turbidity of a backwashing cell, if any. The cumulative effect of several cells running simultaneously but with staggered backwash times guarantees that the individual contribution of one cell will be diminished by the combined high quality effluent of neighboring cells.
Another very important factor to consider is the relative ease of use for operators when it comes to maintenance and troubleshooting. With the built in Sand Movement Verification System, the operator will never be in doubt as to the proper working condition of every airlift in the DynaSand® EcoWash™ Filter. Furthermore, since the airlift is only in operation intermittently, the life of the airlift and the air compressor system are increased significantly.
Testing at the City of Pompano Beach Reuse Facility will continue for the purposes of scientific investigation and the continued collection of data for Parkson’s internal information. We can expect to continue testing a variety of time controlled and differential pressure controlled backwash scenarios to optimize the system even further.