Frequently Asked Questions
1. How much area will an EnviroFilter™ subsurface drainfield require?
Numerous studies have shown that almost all soil types will have a much higher long-term acceptance rate if higher quality effluent is applied to the soil. The higher quality effluent reduces the amount of solids and organics deposited in the soil and prevents a clogging biomat from forming on the soil surface. Based on these studies, high-quality effluent from an EnviroFilter system will require less land area for effluent disposal than that of a standard septic system or typical secondary treatment unit. The local or state regulatory agencies will establish minimum drainfield areas based on their codes. In Florida, the EnviroFilter™ effluent quality is so good that the system is permitted to have the smallest setbacks and drainfield area, and is allowed a reduced vertical separation distance to groundwater when supplemental nutrient removal is added to the system.
2. What is the storage capacity of the system in the event of a power outage?
The EnviroFilter™ recirculation basin is sized for a minimum of one day’s storage capacity so in the case of a power outage there will be at least a full day’s usage available. For longer term power outages, the EnviroFilter™ basin will normally provide a maximum of about 2 day’s storage of influent wastewater. We normally recommend reduced water usage during a protracted power outage to prevent backup into the building or onto the property.
3. What is the treatment level obtained with the System?
Typical EnviroFilter™ effluent is < 5 mg/l BOD, <5 mg/l TSS, < 1 mg/l Ammonia, <20 mg/l Total Nitrogen (with recirculation back to the septic tank), < 2 mg/l P, and > 99.4% reduction of Total Coliform. These quality levels meet or exceed most state requirements. Where local conditions require even lower levels of nutrients (Nitrogen and Phosphorus) or Coliform, the system can be easily supplemented to address the specifics.
4. What level of service is required to ensure proper operation?
The EnviroFilter™ system was designed to be simple and require a minimal amount of service. The system is routinely serviced twice a year at which time the effluent filter in the septic tank is cleaned, the recirculation filter and spray nozzles in the EnviroFilter™ are cleaned, and the pumps and controls are checked for proper operation. The textile chips themselves are self-cleaning during the process and should require no maintenance.
5. Can the system be monitored remotely?
The typical EnviroFilter™ unit is provided with an automatic telephone dialer which will call a sequence of programmed phone numbers during an alarm condition. If more extensive data downloading or remote operations are required, an optional digital programmable logic controller (PLC) can be provided to perform these functions. The EnviroFilter™ control panel can be very basic for very simple operations, or be as complex as the customer desires or the site parameters warrant.
6. What components wear out and will need replacement?
The only typical moving parts on an EnviroFilter™ system are the recirculation and effluent dosing pumps. These pumps are standard off-the-shelf units and normally have about a 15 - 20 year life span before needing replacement. The fiberglass tank and interior piping are designed to last in excess of 100 years. The textile media lifespan depends on the hydraulic and organic loading rates, but is generally design to be greater than 20 years.
7. Where can spare parts be obtained?
All required EnviroFilter™ spare parts and equipment can be obtained from Hydrologex LLC or they can specify the parts to be ordered locally. All system parts and equipment are off-the-shelf items that are readily available from a number of wastewater equipment suppliers
8. What is the typical electricity demand?
The energy requirements of the EnviroFilter™ are among the lowest of all wastewater treatment systems. The EnviroFilter™ utilizes small submersible effluent pumps that run only periodically on a timed basis. For residential systems with electricity costing about $0.08/kw, the average electrical usage would be about $0.39 per day.
9. What happens to the pollutants in the wastewater?
The EnviroFilter™ uses a septic tank for primary treatment. Heavy solids and fats, oils and grease are removed by settling and flotation during the primary treatment process. The septic tank effluent still contains organic material (BOD), suspended solids, ammonia, and pathogenic bacteria and viruses. This effluent is sent to the EnviroFilter™ unit and is mixed with a portion of the water that has already been treated by the EnviroFilter™ unit. This diluted water is then sprayed onto a filter bed comprised of thousands of small textile media chips. These media chips contain beneficial microorganisms that attach themselves to the fibers within the textile media chips. As the wastewater flows through the chips, organic material and suspended solids are removed from the water and are utilized by the microorganisms for food. Other bacteria convert ammonia to nitrates, and pathogenic bacteria and viruses are also removed by the biological process. Most of the effluent that has trickled through the textile chips gets recirculated back over the chips to ensure complete breakdown; a smaller portion goes to the tank that gets discharged.
10. How does the filtration media stay clean/unclogged?
As noted above, the EnviroFilter™ uses a septic tank for primary treatment. Heavy solids and fats, oils and grease are removed by settling and flotation during the primary treatment process. This is very important so that the media is not overloaded by these materials. The EnviroFilter™ uses a recirculation process so that very dilute wastewater is applied to the filter media. Typically, there are 3 to 5 parts of clean water mixed in with each part of septic tank effluent before it is applied to the filter media. This dilution process allows the filter media to be very lightly loaded with biodegradable materials that are completely broken down within the filter bed, leaving clean water and very few solids to plug the media.
11. How long does the textile media last and why doesn’t it plug up?
The EnviroFilter™ textile media is designed to last more than 20 years before it would need to be cleaned or replaced as long as it is not overloaded. Hydrologex carefully designs its textile media filter systems based on calculated organic and particulate loadings of influent. As long as the loadings are kept within the design limits (which are generous), the recirculating media filter will operate and perform well for many years (a generation or more) without clogging. A solids balance for a typical recirculating textile media filter is presented below for illustration, showing that if the filter is loaded within its design limits, it will take a very long time to clog.
Typical Solids Balance for an EnviroFilter™
Textile Media Filter The following solids balance for an EnviroFilter™ recirculating textile media filter will consider how long it will take to fill just half of the void space in the upper 12 inches of a 2 foot thick textile media filter bed, assuming that 60 percent of the material retained in the filter is accumulated in the upper portion of the bed. The following conditions apply:
1. Filter depth = 0.6 m (2 feet)
2. Textile media porosity = 90%
3. Average hydraulic loading rate = 815 L/sm/d (20 gpd/sft)
4. Typical domestic wastewater septic tank effluent BOD concentration = 140 mg/l
5. Filter effluent BOD = 5 mg/l
6. Typical domestic wastewater septic tank effluent TSS concentration = 30 mg/l?
7. Filter effluent TSS = 5 mg/l
8. Typical domestic septic tank effluent VSS = 80%
9. Typical domestic wastewater septic tank effluent FOG concentration = 15 mg/l
10. Filter effluent FOG = 3 mg/l
11. Assume 60% of the FOG is biodegraded
12. Portion of septic tank effluent TSS associated with influent BOD = 80%
13. Net biological yield = 0.2 cells/mg BOD converted (organisms in the filter are assumed to be in the maintenance phase)
14. Net biological yield = 0.3 cells/mg FOG converted
15. Specific gravity of the accumulated solids = 1.125
1. Determine the mass of TSS applied to the filter, for a unit surface area of 1.0 sm:
Mass TSS = (30 mg/l)(815 L/sm/d)(1.0 sm)(365 d/yr)(1/1000 mg/g) = 8,924.3 g/yr
2. Determine the mass of influent TSS remaining after degradation:
Mass TSS remaining = (8,924.3 g/yr)(1 - 0.8) = 1,784.9 g/yr
3. Determine the mass of biological solids produced from the BOD:
Mass BOD = (140 mg/l - 5 mg/l](0.2 cells/mg)(815 L/sm/d)(1.0 sm)(365 d/yr)(1/1000 mg/g) = 8,031.8 g/yr
4. Determine the mass of TSS in the effluent:
Mass TSS effluent = (5 mg/l)(815 L/sm/d)(1.0 sm)(365 d/yr)(1/1000 mg/g) = 1,487.4 g/yr
5. Determine the mass of FOG applied to the filter:
Mass FOG = (15 mg/l)(815 L/sm/d)(1.0 sm)(365 d/yr)(1/1000 mg/g) = 4,462.1 g/yr
6. Determine the mass of biological solids produced from the FOG:
Mass FOG biological solids = (4,462.1 g/yr)(0.6)(0.3) = 803.2 g
7. Determine the mass of FOG remaining after degradation:
Mass FOG remaining = (4,462.1 g/yr)(1 - 0.6) = 1,784.8 g/yr
8. Determine the mass of FOG in the effluent:
Mass FOG effluent = (3 mg/l)(815 L/sm/d)(1.0 sm)(365 d/yr)(1/1000 mg/g) = 892.4 g/yr
9. Determine the mass of solids accumulated in the filter:
Accumulation = inflow (remaining after degradation) - outflow + generation = 1,784.9 g/yr (TSS) + 1,784.8 g/yr (FOG) - 1,487.4 g/yr (TSS) - 892.4 g/yr (FOG) + 8,031.8 g/yr (BOD) + 803.2 g/r (FOG) = 10,024.9 g/yr
10. Determine the time to fill half the filter void space in the upper 12" (0.3 m) of the filter:
a. Volume of solids accumulated per year = (10,024.9 g/yr / 1.125) x (1.0 L/1000g) = 8.9 L/yr
b. Void volume of upper 0.3 m of filter = (1.0 sm x 0.3 m)(0.90)(1000 L/cm) = 270 L
c. Time to fill half of the void space in the upper12" (0.3 m) of the filter
Time = (270 L x 0.5) / (8.9 L/yr x 0.6) = 25 years
In the above calculations it is assumed that the oil and grease are soluble and are not reflected in the TSS and in the conventional BOD test. The computations make it clear that a filter will last a very long time if not overloaded.
12. Does the textile media ever need to be replaced?
The EnviroFilter™ textile media typically never needs replacement. If the media is overloaded and becomes plugged, the media can be cleaned as follows:
a. Flood the tank with clean water until the media is submerged and floating.
b. Add liquid laundry detergent to the water in the media compartment and mix the media with an air compressor.
c. Continue mixing and adding detergent until the media is flowing freely in the basin and solids are emulsified into solution.
d. Pump the dirty water from the pump compartment while still mixing the media until all of the dirty water is removed from the system.
e. Place the system back in operation.
13. What is the performance difference between textile chips, as in the EnviroFilter, and textile sheets, as in the AdvanTex filter?
Studies by third parties have documented that the textile chips produce higher quality effluent and have less risk of plugging during periods of high loading. Click here for the study from the National Environmental Services Center (NESC) PDF, with some portions quoted in the EnviroFilter Overview section under The Efficacy of Textile Chips.
14. Is the EnviroFilter an aerobic treatment unit? Does it have NSF Approval Standard 40?
The EnviroFilter™ relies on an attached growth aerobic treatment process, but is not a typical aerobic treatment unit (ATU) that utilizes a suspended growth activated sludge process. A typical ATU consists of a tank with a blower that runs continuously to provide air to grow microorganisms that are suspended in the water. The tank also contains or is connected to a settling tank to allow the suspended microorganisms to settle to the bottom of the tank so the effluent can be removed from the surface. Because there was so much variability in the performance of these systems, many states required that these systems all be certified by NSF under its Standard 40 to be approved for residential wastewater treatment in that state. That standard, which only applies to units processing 400 to 1500 gallons per day (essentially single-family homes), qualifies systems that meet effluent quality levels of 30 mg/L BOD and 25 mg/L TSS. The EnviroFilter™ achieves effluent quality levels far better than this (below 5 mg/L BOD and TSS) and does not present the other installation, monitoring and performance variability issues that the standard was designed to address, so it currently does not have NSF Standard 40. Many other states allow the EnviroFilter™ to be used for residential treatment based on testing data and long-term performance data that establish that the EnviroFilter™ effluent quality far exceeds the requirements of NSF Standard 40. NSF standard 40 does not apply to non-residential systems or systems with effluent flows greater than 1,500 gallons per day.
15. Is the EnviroFilter™ approach a new technology?
The EnviroFilter™ utilizes a modernized, significantly improved form of the age-old trickling filter process. This process, using sand, stone or gravel as the filtering media because is was so prevalent, was first used early in the 20th century as some of the first wastewater treatment processes in the United States. Many trickling filters are still being utilized by communities today because they are effective and require minimal operation and maintenance. The EnviroFilter™ employs some very important improvements to the trickling filter process. The proprietary textile chip media, a modern highly engineered material, is an enormous improvement over stone or gravel media because it has much more surface area per cubic foot of material. The media also has much more pore space than gravel which helps prevent clogging and allows higher loading rates. Another major improvement is the placement of all the components of the system into a single container so that it can be delivered to the job site ready-to-install as a package system. This reduces the installation labor requirements and helps prevent construction quality control issues in the field. So the EnviroFilter is really uses modern science to improve on a process that has been around for a long time.
16. How can you reduce the size of packed bed filter so that it can fit into a single container?
The key to the EnviroFilter™ system design is the textile media. Because of its porosity, surface area, and weight it allows a loading rate much higher than sand or gravel, peat, or foam. Because of the higher loading rate, the system can be sized to fit into standard size fiberglass, polyethylene or precast concrete tanks.
17. What makes textile media perform better than traditional sand or gravel media as the filter?
As noted above, the textile media has a much higher water loading rate that sand or gravel due to its fiber surface area and porosity. Even with a higher loading rate, the textile media performs as well or better in effluent quality to sand or gravel media. The textile media also tends to plug less often than sand or gravel because its porosity allows a deeper penetration of material into the bed instead of immediately plugging the surface. For more detail, see the section under EnviroFilter Overview titled “The Efficacy of Textile Chips”.
18. How can the loading rate of the EnviroFilter be so much greater than the recirculating sand filters?
The sand filter hydraulic and organic loading rates have developed empirically over many years based on actual system operations. These loading rates are well-established and have been proven to provide decent service over the life of the system. The EnviroFilter™ textile media has about three times the surface area and porosity of the sand media used in conventional recirculating sand filters. This allows the EnviroFilter™ to be successfully loaded about three times greater than typical recirculating sand filters.