273 Weymouth St., Rockland, MA 02370   (781)982-9300 fax (781)982-1056

US EPA Environmental Technology Initiative
Onsite Wastewater Technology Testing Report

The Amphidrome® belongs to a broad class of treatment units called sequencing batch reactors (SBRs). These units process wastewater in "batches" and usually discharge the treated batch of wastewater over a short period of time to ready itself for the incoming load.

The Amphidrome, as configured during these tests, consisted of a 1,500 gallon septic tank (anoxic chamber), a cylindrical reactor vessel (2 ft in diameter x 10 ft in height), and a 500 gallon clearwell from which the final treated effluent was pumped to the soil absorption system (Figure 1). All three replicates were supplied process and backwash air using pumps located remote to the unit and in the same housing. Based on the results of these tests, the vendor recommends the use of a 2,000 gallon septic tank for residential applications in this design-flow range.

Relative component elevations are critical to proper system performance. Height of the reactor vessel may complicate some shallow-to-groundwater installations. Installation requires significant training and/or oversight by manufacturer. Above ground components include a blower with housing (variously sized), and an electrical control with an audio and visual alarm. The control panel contains programmable logic controllers (PLC) that require manufacturer's adjustments. Design considerations include the location of access

Figure 1. Illustration of the Amphidrome® sequencing batch reactor as configured for testing at the Massachusetts Alternative Septic System Test Center.

manhole covers for routine maintenance and sampling, and situating the blower to minimize possibility for noise disturbance.

This system directs wastewater back and forth between the septic tank (anoxic tank) and the "clear well," passing it through an aggressively aerated reactor vessel. During this aeration part of the cycle, the effluent is nitrified (ammonium is converted to nitrate). At preset intervals, the air supply to the reactor vessel is shut off, allowing anoxic conditions to develop and enabling denitrification (i.e., conversion of nitrate to nitrogen gas) to occur. When the wastewater "batch" is adequately treated (cycled a number of times), it is discharged to the Soil Absorption System (SAS) at predetermined intervals. Processes are time-controlled using a series of programmable logic controllers.

Non-Standard Components: $8,000 (with clearwell, claim). Components + Installation: $10,000 more than conventional (claim). Electrical: $140-150 per year actual (assuming $0.10/ KWh and 3.9 KWh/day). These electrical costs reflect the system loaded continually at the peak (330 gpd) design flow. The vendor claims that under more typical actual flows, electrical costs will decrease based on the decreased pumping and air supply needs. O&M: Quarterly inspection of motors, air flow, effluent and sludge. A service contract is required in Massachusetts (Approximately $400 per year minimum, but varies). Septic tank pumping varies with location. Other Costs: Quarterly effluent quality monitoring is required for some permits ($300 or more annually). Design and permitting costs vary. Replacement: Pumps and blowers ($300) have a one-year warranty by Amphidrome.

The testing duration was two years. The technology was installed in triplicate, with identical components. The Amphidrome received wastewater at the rate of 330 gallons per day, throughout the two-year testing period. The 330 gallon per day volume is the Massachusetts Department of Environmental Protection (MA DEP) minimum design flow for a new residential house of three bedrooms or less.

Delivery of the wastewater was apportioned into fifteen equal doses of 22 gallons each, on a schedule which was designed to mimic the pattern of wastewater use in a typical residence (35% of flow in the morning; 25% flow during midday; 40% in the evening; see ETI QAPP and NSFI/AINSI Standard 40). Periodic calibration of dose volumes delivered to each technology ensured equal dosing to each replicate and to different technologies.

Effluent from the technology flowed to a distribution box and exited to the soil absorption system (SAS) through a single 4’ pipe. The resulting load to the SAS was approximately 3 gal/day/sq ft. Pan Lysimeters were installed at depths of one, two and five feet beneath each SAS to collect leachate for analysis. A polyethylene liner with sump collected all leachate from the three technology replicates.

The technologies were sampled at two-week intervals. During each sampling event, technology influent wastewater was sampled at the common source. Technology effluent was sampled at the distribution box. Influent wastewater and technology effluent were sampled using automated samplers, programmed to obtain fifteen flow-weighted samples and composited over a twenty-four hour period. Since the discharge of this technology occurs in a single event, a sample container was positioned at the discharge point to collect a single sample from each unit.

Composite and discrete samples were kept refrigerated at 4 degrees centigrade either by ice packed in the sampler or by use of a refrigerated sampler. Analysis for pH and specific conductance were conducted at MAASTC during sample processing. Subsamples for BOD5 and fecal coliform were sent to the Barnstable County Department of Health and the Environment laboratory. Subsamples for nitrogen and phosphorus analysis: ammonium (NH4), nitrate plus nitrite (NOx), dissolved organic nitrogen, (DON), particulate organic nitrogen (PON), alkalinity, orthophosphate (PO4) and total phosphorus (TP); were sent to the Coastal Systems Laboratory at the School for Marine Science University of Massachusetts, Dartmouth (SMAST).

Electrical usage was measured by a single electric meter for all three units and recorded monthly. Kilowatt usage was then divided by three to calculate individual unit use.

Alarms, mechanical failures, unusual sounds, and smells were recorded in a logbook as they occurred. Restorative measures taken by the technology vendor to address non-normal conditions were also recorded and appear in Section 6 "Operation and Maintenance" section of this report.

The three replicate systems were installed in early December, 1999, and their operation was officially started for the beginning of testing on February 14, 2000. In early November, 2000, operation of one replicate system (referred to as "B-1") was ceased in order to prepare the unit for testing under a different set of protocols referred to as the Environmental Technology Verification Program Protocols. These later results are reported under a different cover. The two remaining units were operated and tested until April, 2002.

The Amphidrome was tested to demonstrate removal of nitrogen from the influent wastewater.

BOD5 effluent data suggest that the Amphidrome® system requires little startup time for the reduction of this constituent. The mean BOD5 at the discharges (combining all three units) was 17.9 mg/l (n=134) versus a mean influent level of 195 mg/l (n= 58) representing a 90.3% removal rate (Table 1, Appendix 1, Appendix 2). Excursions from the secondary-treatment standard of 30 mg/l appear related to a sludge buildup in the system that began after approximately eighteen months of operation. Following the removal of sludge from the first (anoxic) tank of units #2 and #3 (B-2 and B-3) on August 3, 2001, the removal performance of the system for this constituent returned within a few weeks (BOD was 5 mg/l or less on August 28, 2001). The failure of a process blower on the third replicate system (B-3) caused the BOD levels after March 26, 2001 to exceed the secondary standard of 30 mg/l.

The removal of suspended solids by the Amphidrome followed a similar trend as treatment for BOD, with only minor exception (Table 2, Appendix 1, and Appendix 2). Following approximately eighteen months of operation sludge accumulation of sludge in the anoxic chamber resulted in increased carryover of suspended solids to the discharge. Similar to the trend with BOD, suspended solids decreased in the discharges following the removal of sludge from the anoxic chamber on August 3, 2001. The single high TSS value (42. 7 mg/l) at B-3 (replicate #3) on August 28,2001 is unexplained, but could be due to an inadvertent mislabeling/switching of the sample bottle B-3 with that of B-1. This is corroborated by the BOD level at B-1 (which was not being tested under the ETI protocols at the time) which shows a concurrent BOD of 22 mg/l, more likely to coincide with the higher TSS. Likewise, the BOD of 5.0 mg/l noted at B-3 more likely coincided with a TSS of 2.9 mg/l which was reported to be observed at the B-1 discharge (Appendix 1, Appendix 2).

Table 2. Total Suspended Solids (TSS) removal performance of the Amphidrome® system during testing at the Massachusetts Alternative Septic System Test Center. February, 1999- March 2001.

With a single exception, all three replicates of this technology were consistent with each other for the first eight months of operation. The single exception observed on June 14, 2000 at B-2 (Replicate #2) is unexplained and may be due to laboratory error since it is highly inconsistent with both the replicates and values noted on dates either side of this observation.

Table 3. Total Nitrogen (TN) removal performance of the Amphidrome® system during testing at the Massachusetts Alternative Septic System Test Center. February, 1999- March 2001. Data below exclude a start-up period of February 23-May 2, 2000.

For the calculation of nitrogen removal, data following a start-up period was used. For purposes of this report, "start-up" is considered as that period during which the total nitrogen level (mg/l) in the discharge exceeds 19 mg/l. In the case of the Amphidrome, there is a clear demarcation of start-up at the 12 week sampling event (Appendix 1, Appendix 2). Prior to this (on May 2, 2/000), all units show a Total Nitrogen (TN) level exceeding 22 mg/l. On May 17, 2000, no replicate discharged levels of TN exceeding 13 mg/l. Thus, when the Amphidrome is started during colder months, at least a 12 week start-up appears to be required. In the period following start-up (May 17, 2001 to April 24, 2001), the average TN discharged (excluding the one aberrant value of 27.3 mg/l observed at B-2 on June 14, 2000) was 9.14 mg/l (n=61). Following this date, however, and until sludge accumulation in the anoxic tank was removed on August 3, 2001, TN levels averaging 20.3 mg/l (n=14) were discharged. This observation suggests that the nitrogen removing capability of the system is even more sensitive to the buildup and accumulation of sludge in the anoxic chamber compared with BOD and TSS. Again, following the removal of accumulated sludge on August 3, 2001, treatment for nitrogen resumed with average levels of 8.6 mg/l (n=36) observed until the end of sampling on April 23, 2002. This average excludes two high (26.3 and 37.8 mg/l) levels observed at B-3 due to a failure of a process blower in early April of that year.

Our data indicate that, following a start-up period which may vary depending on ambient temperature, this system is capable of achieving discharge levels of < 12 mg/l, provided that sludge levels are not allowed to accumulate, and the system components are otherwise maintained in accordance with the manufacturer’s recommendations. The reason for the lower mean nitrogen levels in Replicate #1 compared with #2 and #3 (Table 3) is that this unit was halted prior to the accumulation of sludge1.

Fecal coliform is often used as a surrogate measure of public health significance. Wastewater treatment systems that remove fecal coliform are thought to concurrently reduce the discharge of human pathogens. In general, there is 1- 2log (90-99%) removal of fecal coliform in the Amphidrome system, with no apparent seasonal trends in performance.

Table4. Fecal Coliform removal performance of the Amphidrome® system during testing at the Massachusetts Alternative Septic System Test Center. February, 1999- March 2001.

1 B-1 or Replicate #1 was cleaned and restarted for testing under Environmental Technology Verification Protocols which will be reported under separate cover.

In general, the Amphidrome System requires that the operator of the system begin with an approximate set of settings for the various cycles that may not reflect settings for optimum performance. Accordingly, at any site, a period of adjustment must occur. During our testing, between the period 3/17/2000 – 5/18/2000, the operator made adjustments at least 12 times. The vendor collected and analyzed many discharge samples throughout the testing period using field test kits. This practice was presumably to indicate what field adjustments were necessary to the operating parameters. Adjustments were periodically made to all units during the entire testing period. The relatively high number of adjustments were made presumably due to the fact that the units installed were among the first units designed for single-family usage.

During the testing period, a float switch was replaced (8/15/01), and a motor was replaced (11/13/01). The vendor believed that the motor replacement resulted from an electrical surge, possibly a strike by lightning.

The Programmable Logic Controllers installed in the three units tested did not have internal clocks. The lack of this feature resulted in occasional disruption of the cycle times at times when the facility experienced power failures. Internal clock mechanisms will presumably be placed in any models sold after our testing dates.

The noise generation of the unit was difficult to measure due to the fact that the blowers for all three units were placed in the same housing and operated simultaneously.

The components of the Amphidrome must only be serviced by qualified personnel. Sludge levels can be determined using a standard "sludge judge" or other manual type device, or using various electronic devices. The manufacture states that annual pumping is recommended on systems configured similar to the units tested. The reactor vessel can easily be inspected by opening the circular top, which allows access to control and alarm floats for inspection and testing. Similarly, the clearwell is accessed by opening the top, which allows inspection of both pumps and control floats. The electrical panel houses the PLC and controls for access by a computer or similar device. Manual overrides of pumps and blowers, as well as alarm switches were easily accessible for inspection/testing. As with all advance treatment units in Massachusetts, the unit must be under a contract for the operation maintenance for the life of the system. DEP requires that the operator of this system must hold a Class 4 Wastewater Treatment Plant Operator certification.