Progress Report

CICEET Progress Report for the period 3/15/05 Through 9/15/05

Project Title: Evaluation of Leachfield Aeration Technology for Improvement of Water Quality and Hydraulic Functions in Onsite Wastewater Treatment Systems
Principal Investigator(s): Jose A. Amador
Additional Investigator(s): David A. Potts, Josef H. Gorres, George W. Loomis, Erika L. Nicosia
Project Start Date:1 September 2004

Figures
Figure 1

Figure 1
Figure 2

Figure 2
Figure 3

Figure 3
Figure 4

Figure 4
Figure 5

Figure 5
Figure 6

Figure 6
Project Objectives for This Reporting Period
Objectives
A. Pilot-Scale Experiments - Loss of Aeration (LOA)
B. Pilot-Scale Experiments - Increased Hydraulic Load (IHL)
C. Field Scale Experiments - Protocol Development and Site Identification

Tasks to meet objectives
Objective A: Pilot Scale Experiments - Loss of Aeration (LOA)

  1. Baseline data collection to confirm equilibrium
  2. Switch off aeration to AIR lysimeters for 48 h
  3. Restore aeration to the AIR lysimeters
  4. Post-disturbance data collection
  5. Monitor for new equilibrium

Objective B: Pilot Scale Experiments - Increased Hydraulic Loading (IHL)

  1. Baseline data collection to confirm equilibrium
  2. Double wastewater hydraulic loading to AIR lysimeters for 48 h
  3. Restore previous wastewater hydraulic loading to AIR lysimeters
  4. Post-disturbance data collection
  5. Monitor for new equilibrium

Objective C: Field Scale Experiments - Protocol Development and Site Identification

  1. Develop protocol for field site selection
  2. Develop list of potential sites
  3. Perform on-site evaluation and final selection
  4. Install systems, instrument sites

Progress on Tasks
Objective A: Pilot Scale Experiments - Loss of Aeration (LOA)
The purpose of the LOA experiment was to measure the system’s response to loss of electrical power/mechanical failure of blower, which in the treatment system under study results in loss of aeration. Since at least some of the water quality functions - particularly N removal - require alternating aerobic and anaerobic conditions, examining the system’s robustness with respect to loss of aeration is an important aspect of the evaluation of this technology.

  1. Baseline data (quality of water draining from lysimeters, headspace gas composition, removal efficiencies for N, P, BOD5, and fecal coliform bacteria) were collected prior to the loss of aeration (LOA) experiment. Four replicate AIR lysimeters were analyzed for response to LOA.

  2. On 4 April 2005 water quality and gas data were collected, one day prior to the start of the LOA event. The accidental LOA event was simulated by turning the aeration system off the following day, the system remaining off for 48 h - from 5 April to 7 April 2005.

  3. Water quality and gas data were collected immediately after the LOA event ended, and 1, 3, 5, 12, 26 and 39 days after the LOA. These data are described in the Preliminary Data section (below).

Objective B: Pilot Scale Experiments - Increased Hydraulic Loading (IHL)
The purpose of the IHL experiment was to assess the robustness of the system with respect to a sudden, short-term increase in hydraulic load to a leachfield. This is a common challenge to domestic septic systems that can result from changes in household water use that can be recurrent (e.g. laundry day) or sporadic (e.g. visitors).

  1. The IHL experiment was conducted subsequent to the LOA event. Baseline data (quality of water draining from lysimeters, headspace gas composition, removal efficiencies for N, P, BOD5, and fecal coliform bacteria) were collected prior to the increased hydraulic loading (IHL) experiment. Four replicate AIR lysimeters were analyzed for response to IHL.

  2. On 11 May, 2005 water quality and gas data were collected, immediately before the event. IHL was simulated by doubling the number of times the lysimeters were loaded for 24 h. The resulting daily load was 24 cm/d, twice the load (12 cm/d) that was used pre- and post-IHL

  3. Water quality and gas data were collected 1, 5, 8, and 33 days after the IHL experiment. These data are described in the Preliminary Data section (below).

Objective C: Field Scale Experiments - Protocol Development and Site Identification

  1. A meeting of the PIs and End-User was held on 21 April 2005 at the University of Rhode Island. It was attended by Amador (URI), Loomis (URI), Nicosia (URI), Kalen (URI), and Moore (RIDEM). A protocol for field site selection was agreed upon and a timeline for evaluation of site fitness and subsequent preparations for experiment was developed.

  2. Subsequent to this meeting, a list of 25 potential field sites (all state-administered group homes) was developed by Loomis, Kalen, and Moore, in cooperation with personnel with the RI Dept. of Mental Health, Retardation and Hospitals.

  3. Two preliminary field evaluation trips were conducted:
    21 June 2005: Loomis (URI), Kalen (URI), Moore (RIDEM) and Knauss (RIDEM) visited 11 potential sites in Charlestown, South Kingstown, East Greenwich, Johnson, and Gloucester, RI.

    20 July 2005: Kalen (URI) and Jobin (URI) visited an additional 14 potential sites in South Kingstown, North Kingstown, Exeter, and Charlestown, RI.

  4. Based on the information collected in these two dates, a short list of sites for further evaluation prior to final site selection was developed by Loomis and Kalen on 21 July 2005. The list contained 7 failed systems and 10 systems that were working properly.

  5. A visit for final site selection was conducted by Loomis, Amador, Kalen, Gorres, and Potts on 12 September, 2005. We are currently awaiting additional documentation (site plans) which RIDEM has kindly agreed to provide in ourder to finalize our choices.

Difficulties
Pilot-Scale Experiments
No difficulties were experienced in conducting the pilot-scale experiments, which were finished earlier than anticipated.

Field-Scale Experiments
Minor scheduling conflicts have arisen, but they have not affected the timeline for field experiments.

Project Objectives for Next Reporting Period

Work Plan for Next Reporting Period
Sept. 05:     Final field site selection
Oct./Nov. 05:     System installation and site instrumentation
Nov/Dec. 05:     Begin pre-aeration data collection
Dec. 05 - Apr. 06:     Continue pre-aeration data collection

Anticipated Success in Meeting Project Objectives
Barring weather or other unanticipated impediments, the field experiments should move along as originally planned.

Overall Project Timeline Update
One year into the project, tasks are on schedule. The initial, pilot-scale phase of the project was completed earlier than expected and outreach activities have begun earlier than anticipated.

Preliminary Data
Pilot Scale Experiments - Loss of Aeration (LOA)

Effects on rate of removal of N, P, BOD5, and fecal coliform bacteria
The effects of a simulated accidental loss of aeration (LOA) for 48 h on the capacity of AIR lysimeters to remove carbon, nutrients, and fecal coliforms were quickly apparent (Fig. 1), but recovery was also quick.

Removal of total N prior to LOA was near 45% - about the average value observed for this treatment (Figure 1). Twenty four hours after the 48 h LOA period, a statistically significant (repeated measures ANOVA vs control; P < 0.05) net loss of N from these lysimeters was observed. However, 72 h after the end of the LOA period (day 5) net total N removal was observed again, and 10 days post-LOA (day 12) it was in the 60% range. Removal of N continued at or above the average value for AIR lysimeters subsequently.

Total P removal prior to LOA was about 70%, declining significantly at the end of the 48 h LOA period to a minimum of 50% (Figure 1). A return to P removal rates prior to LOA was observed within 10 days of restoring aeration (day 12), with above-average P removal observed subsequently. BOD5 removal rate declined slightly - from 100% to 93% - at the end of the 48 h LOA period (Figure 1). The decline was not equal among all four replicate lysimeters, as indicated by the higher standard deviation observed on day 2, and thus was not statistically significant. Removal of BOD5 returned to pre-LOA values 24 h after aeration was restored (day 3) and remained at that level for the remainder of the experiment.

Rates of fecal coliform bacteria were on the order of 99.9% prior to LOA, and declined to ~99.6% by the end of the 48 h LOA period, although the effect was not statistically significant (Figure 1). As observed for removal of BOD5, the high standard deviation for fecal coliform removal on day 2 indicates that the response of lysimeters to LOA varied considerably among replicates. Fecal coliform removal rates were back to pre-LOA levels 24 h after aeration was restored, and continued at that level for the rest of the experiment.

Effects on water quality
Levels of dissolved oxygen in water draining from the lysimeters diminished from ~8 to 4 mg/L at the end of the 48 h LOA period (day 2), but returned to previous levels once aeration was restored (day 3) (Figure 2). The pH of drainage water was slightly lower in response to LOA, but returned to pre-LOA levels in response to restored aeration. LOA had no immediate effects on nitrate levels, although these were lower than pre-LOA levels in the latter part of the experiment. Ammonium levels remained low throughout the experiment. No Fe (II) was detected in drainage water prior to, during, or after the LOA event (data not shown). Levels of sulfate were also not affected by loss of aeration.

Effects on headspace gases
The composition and concentration of gases in the headspace of AIR lysimeters responded quickly to the LOA event as well as to restoration of aeration (Fig. 3). At the end of the 48 h LOA period (day 2), methane and carbon dioxide concentrations were significantly higher than observed prior to the event, while levels of oxygen were significantly lower (Figure 3). Restoring aeration to the lysimeters resulted in levels of methane, oxygen, and carbon dioxide that were identical to those prior to the LOA event.

Pilot-Scale Experiments - Increased Hydraulic Load (IHL)

Effects on rate of removal of N, P, BOD5, and fecal coliform bacteria
Increasing the hydraulic load from 12 to 24 cm/d had mixed effects on the ability of AIR lysimeters to remove N, P, BOD5 and fecal coliform bacteria.

N removal increased in response to the IHL event (Figure 4). Prior to the event, the total N removal rate was ~50%; at the end of the IHL period a statistically significant increase in N removal was observed, with 75% of the N input removed in AIR lysimeters. N removal rates remained at about 60% 4 and 7 days after the IHL event, returning to pre-event values after 32 days. No effect of IHL on removal of total P was observed (Figure 4).

The IHL event had a statistically significant effect on the rate of BOD5 removal (Figure 4). Prior to the event, removal was at 99%, immediately after the event the rate dropped to 94%. The rate of BOD5 removal returned to pre-event values within four days (day 5) and remained at that level for the rest of the experiment.

Removal of fecal coliform bacteria also declined in response to the IHL event, although the effect was not statistically significant (Figure 4). Removal rates were 99.9% before the event, and 99.5% immediately after. The fecal coliform removal rate returned to pre-event values within four days (day 5) and remained at that level for the rest of the experiment.

Effects on water quality
Levels of dissolved oxygen decreased in response to IHL, but returned to pre-event values within 4 days of returning to basal loading rate (Figure 5). Water pH exhibited a small decline that continued up to 7 days after basal flow was restored, but was back to pre-IHL values 32 days after the event. A slight fluctuation was observed in ammonium and sulfate (increase) and nitrate (decrease) at the end of the 24 h IHL event, but the difference was not statistically significant, and levels of these nutrients returned to pre-IHL event values within 7 days of restoring the load.

Effects on headspace gases
Lysimeter headspace gases were not affected by the IHL event (Figure 6). No statistically significant differences in concentration of methane, oxygen, and carbon dioxide were observed pre- and post-IHL.

Dissemination
Publications:
Amador, J. A., D. A. Potts, E. L. Nicosia, and J. H. Gorres. 2005. Aeration to improve the water quality and hydraulic functions of septic system leachfields. Proc. 13th Northwest On-Site Wastewater Treatment Short Course and Equipment Exhibition, Seattle, WA.

Workshops:
22 March 2005: OWT 105 - Innovative & Advanced Technology Overview Course. Led by Loomis and Kalen and attended by 16 professionals. 23 June 2005: I & A Tour - Innovative & Advanced Technology Field Tour for Wastewater Professionals. Led by Loomis and Kalen and attended by 18 professionals.

Conferences:
Amador will be giving an invited presentation entitled “Aeration to Improve the Water Quality and Hydraulic Functions of Septic System Leachfields” at the13th Northwest On-Site Wastewater Treatment Short Course and Equipment Exhibition, sponsored by the Univ. of Washington, Seattle, WA on September 19- 20, 2005.

Manuals, Protocols: None

Outreach Activities:
2 April 05: Amador and Gorres conducted a lab tour and inquiry exercise on water pollution by septic systems with a group of 15 middle school students that participate in the Rhode Island Science and Math Investigative Learning Experience (SMILE) program. Individuals in the SMILE program are academically-talented students that come primarily from economically-disadvantaged and/or minority households.

Contact with End Users:
End user has been actively involved in helping us with the field site selection process, including attending PI meetings (11 April 05), facilitating inter-agency communications (RIDEM - RIDMHRH) necessary for site selection, going on preliminary site identification visits (21 June 05), and making drawings and other important information necessary for final site selection available to the PIs.

Patent, Copyright, Invention Disclosure Activity: None

Expenditures
Expenditures are somewhat lower than expected at this point of the project.

End User Advisor Feedback
Name: Brian M. Moore
Organization: RI DEM
Location: 235 Promenade Street, Providence, RI 02908
Phone number: (401) 222-4700 Ext. 7713
E-mail: brian.moore@dem.ri.gov

1) At this stage, what are the potential applications for this research? Please discuss how you and others could potentially use the technology.
Renovate existing failed drainfields, with minimal site disturbance.

2) What, if anything, has changed about this project's potential applicability since the last reporting period (not applicable to the first Progress Report)?
Field investigations of potential test sites have shown the need and potential for this technology.

3) Do you see any key challenges that the researchers may want to address or keep in mind?
Siting considerations, aesthetics of putting units into place.

4) Does this report offer you enough information to adequately address the above questions?
Yes

5) Other feedback?
No