A carbon footprint analysis was performed comparing tertiary filtration technologies: the Kruger Hydrotech Discfilter and conventional sand filters. The Hydrotech Discfilter employs woven cloth filter elements installed vertically on multiple discs, supplying a large filter area within a small footprint. The conventional sand filter is a rapid gravitational filtration of raw water through a granular media. The filtering bed is composed of a single sand layer.
Technology Design Data
A carbon footprint analysis for both tertiary filtration systems were based on the same criteria:
|Peak Influent Flow|
1,080 m3/hr (6.85 MGD)
|Average Influent Flow|
540 m3/hr (3.42 MGD)
|Peak Infulent TSS|
|Average Influent TSS|
|Target Final Effluent TSS|
≤ 5 mg/L
One (1) Hydrotech Discfilter model HSF-2224-1F, consisting of 24 discs and stainless steel tank, was used within the analysis. The conventional sand filter system was deigned with four (4) parallel filtration cells.
The carbon footprints of each process were analyzed from the standpoint of construction, equipment and operation. The carbon footprint attributed to construction includes the resources necessary to create the materials used, shipping and installation of the equipment and materials.
Electricity, consumed media and freight to transport media (filter panels or sand and gravel) were considered in the operational footprint. System disposal and transport of backwash were not considered.
Since the source of electricity varies throughout different regions of the United States, three different regions were selected to quantify the sensitivity of the electrical emission factor to the total carbon footprint. On the low end, the northwest US (EPA eGRID subregion NWPP) had an approximate emission factor of 0.41 kg equivalent CO₂ per kWh, while the Florida region had a higher end emission factor of 0.60 (EPA eGRID subregion FRCC), and the U.S. average is approximately 0.58. The three regions are depicted in graphs herein as "Low", "Avg." and "High".
Total Lifetime Equivalent CO2 Emissions with Varying Electrical Emission Factors
The Discfilter has a 46% smaller carbon footprint than the conventional sand filter based on average U.S. emission factor for electricity. The Discfilter's energy efficient design, using low hp pumps, and an efficient backwash method, is a major contributor to it's smaller carbon footprint.