CICEET Progress Report for the period 3/16/06 Through 9/15/06

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, Professor, Univ. of Rhode Island
Additional Investigator(s):
David A. Potts, President, Geomatrix, LLC, Killingworth, CT
Josef H. Gorres, Associate Research Professor, Univ. of Rhode Island
George W. Loomis, Research & Extension Soil Scientist, Univ. of Rhode Island
Erika L. Patenaude, Research Assistant, Univ. of Rhode Island
Project Start Date: September 1, 2004

Figures

Figure 1

Figure 2

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Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Tables

Table 1

Table 2

Tasks to meet objectives
Objective A: Pre-aeration data collection
Monitoring of sites has taken place nearly every two seeks since 9 March 2006. Samples of septic tank effluent have been obtained. In addition, water samples have been obtained (using cup lysimeters) from three areas within each site: (i) upgradient from the leachfield, (ii) between leachfield trenches, and (iii) immediately downgradient from the last leachfield trench. In each area samples have been collected from 30 and 90 cm below the infiltrative surface The samples are analyzed for Total N, ammonium, nitrate, total P, phosphate, dissolved organic C, sulfate, reduced iron, chloride, and fecal coliforms. The temperature of all water samples is measured. In addition, the composition of gases in the soil atmosphere (O₂, CH₄, CO₂, H₂S) has been monitored.

Objective B: Installation of SoilAir Systems
An agreement to install, operate and maintain (IOM) the SoilAir Systems was sent by Mr. David Potts, president of Geomatrix, LLC to Mr. Steven Denoyelle, of the RI Dept. of Mental Health, Retardation, and Hospitals (MHRH) on 1 June 2006. A meeting is planned for the week of 9-18-06 with URI, RI Dept. of Environmental Management, MHRH and Geomatrix, to work through any outstanding details.

Objective C: Evaluation of effects of aeration on hydraulic function and water quality
Progress on this objective has not been made because MHRH has been unable to provide feedback to the proposed IMO Agreement.

Progress on Tasks
All of the tasks necessary to commence monitoring of water quality parameters prior to bringing the SoilAir systems online have been completed and water quality monitoring is underway.

Difficulties
It has taken longer for MHRH to respond to the proposed IMO Agreement than anticipated. This has resulted in delay of the start of the technology evaluation phase of the project. Nevertheless, installation in the next few weeks should provide us with approximately 5 months of time for evaluation, on track with the evaluation time proposed originally.

Project Objectives for Next Reporting Period

Objectives
Objective A: Installation of SoilAir Systems
Objective B: Evaluation of effects of aeration on hydraulic function and water quality

Tasks to Meet Objectives
Tasks to Meet Objective A:
    1. Meeting with all interested parties to finalize terms of IMO Agreement
    2. Installation of SoilAir Systems

Tasks to Meet Objective B:
    1. Commence operation of SoilAir Systems
    2. Monitor water quality parameters and gas composition biweekly (as described under Preliminary Results, below) as well as hydraulic function.
    3. Compare pre and post-aeration data

Anticipated Success in Meeting Project Objectives
Aside from the normal delays caused by weather and scheduling conflicts, we anticipate no problems in meeting the project objectives listed above.

Overall Project Timeline Update
We are approximately 2 months behind schedule in the field phase of the project. We requested ­ and were granted ­ a 6-month, no-cost extension to complete the project.

Preliminary Data
Description of Study Sites
A total of 6 sites were instrumented in February 2006 and have been monitored for the past six months. The sites consist of group homes managed by the RI Dept. of Mental Health and Rehabilitation in Washington County, RI, with three sites in Charlestown, two in South Kingstown, and one in Exeter (Table 1). Five of the six systems rely on leachfield trenches for septic tank effluent dispersion, with galleys employed in the remaining system.

Each septic tank is fitted with a pipe placed near the tank outlet a depth of 45 - 60 cm below the effluent level for sampling. The sites are instrumented with three clusters of ceramic cup lysimeters and/or slotted wells. Cluster locations within a site are as follows:
Cluster 1 (C1): Upgradient from leachfield
Cluster 2 (C2): Between leachfield trenches or galleys
Cluster 3 (C3): Downgradient from leachfield, immediately adjacent (15 - 20 cm) to outer wall of last trench or galley

Within each cluster, sampling devices were installed as follows:
Lysimeters: Bottom of cup at a depth of 30 and 90 cm below infiltrative surface (designated C1-30, C1-90, C2-30, C2-90, C3-30, C3-90).
Wells: Slotted (15-30 cm) section partially or completely below groundwater level at time of installation (designated C1-W, C2-W, C3-W).

Three of the six sites (Sites 1, 4 and 5) have the full complement of instrumentation (Table 1). Site restrictions prevented installation of C1 at Site 2, of groundwater wells at Site 3, and of the C2 groundwater well at Site 6.

Sampling
The values reported here are for the following sampling dates, all in 2006: 9 March, 23 March, 6 April, 20 April, 4 May, 18 May, 1 June, 15 June, 6 July, and 20 July. Data from more recent sampling dates (8 August, 24 August, 8 September) are currently being analyzed and thus are not included in this report. Groundwater wells were pumped 24 h prior to sampling using a peristaltic pump. In instances when the well could not be pumped to dryness, the volume of water pumped was at least 5 times the standing volume. A hand pump was used to apply a vacuum (~ 80 kPa) to the lysimeters 24 h prior to sampling.

Samples of water from wells and lysimeters, as well as septic tank effluent samples, were collected using a peristaltic pump fitted with silicon tubing. Water samples were placed in autoclaved polyethylene screw-cap bottles and stored in a cooler filled with ice packs immediately after collection. Samples of soil gases were drawn from the wells after water samples were removed.

Analyses
Septic tank effluent was analyzed immediately for dissolved oxygen (DO). The temperature and concentration of Fe²⁺ of samples of STE and of water from wells and lysimeters were also determined immediately after sampling.

All samples were assayed for pH immediately upon arrival to the laboratory before filtering. Unfiltered STE samples were also assayed for biological oxygen demand (BOD5) fecal coliforms and Escherichia coli, and unfiltered well water samples were analyzed for fecal coliforms and E. coli. A portion of all unfiltered samples was frozen for subsequent determination of total N (TN) and total P (TP) content. The remaining sample was filtered by passing through a nylon membrane filter (MAGNA, 0.45-_m pore-size, 47-mm dia., Osmonics, Watertown, MA) and the filtered samples stored in plastic, screw-cap vials at 4°C.

Soil gases were sampled and analyzed using a portable soil gas monitor (SoilAir Technology, Killingworth, CT). CO₂, CH₄, O₂, and H₂S were determined using infrared, catalytic bead, galvanic, and electrochemical sensors, respectively. Gas samples were drawn at a rate of approximately 0.05663 m³ h^-1 (2.0 SCFH) for 30 to 60 s and the maximum values detected during that sampling period are reported for all gases except O₂, for which the minimum value is reported.

Water temperature was measured using a Fisherbrand traceable digital thermometer with stainless steel stem (Fisher Scientific, Pittsburgh, PA). Constituent analyses were performed according to Standard Methods for the Examination of Water and Wastewater (APHA, 1998). DO was measured using the azide modification of the Winkler titration method. The concentration of Fe²⁺ in water was determined using EM Quant ® Iron (Fe²⁺) Test strips (EM Industries, Inc., Gibbstown, NJ). The pH of water samples was determined using a combination pH electrode and a model UB-10 pH meter (Denver Instruments, Denver, CO). The concentration of sulfate was measured using the barium chloride turbidimetric method. Nitrate, ammonium, and phosphate concentrations of water samples were determined colorimetrically using an automated nutrient analyzer (model Flow Solution IV, Alpkem, College Station, TX). The total N and total P content of water samples was determined using the persulfate digestion method. Samples were digested by autoclaving at 121°C and analyzed colorimetrically for NO₃^- and PO₄^3- as described above. Fecal coliforms and E. coli were assayed using the standard total coliform membrane filtration procedure. BOD₅ was measured on undiluted, unamended samples by manometric respirometry using an OxiTop® BOD system (WTW, Fort Myers, FL) at 21+1°C. The total organic carbon (TOC) content of filtered samples was determined using a TOC-5000A Total Organic Carbon Analyzer (Shimadzu Instruments, Inc., Laurel, MD).

The apparent removal rate, R, for N, P, Cl, and TOC was calculated using the equation:
R = 100 X [(C_STE - C_L)/C_STE]   [Eq. 1]
where C_STE is the concentration of a constituent in septic tank effluent and C_L is the concentration in a sample from a lysimeter.

Results
Temperature. Mean STE temperature ranged from 18 to 22°C (Figure 1). Water samples from upgradient lysimeters (C1) were between 5 and 11°C colder than STE values, with temperature ranging from 11 to 13°C. The mean temperature of water from lysimeters between (C2) and downgradient from (C3) the trenches was between values for STE and C1.

pH. STE samples had mean pH values ranging from 6.5 to 6.7 (Figure 2). The pH of water from C1, C2, and C3 differed little from that of STE for Sites 2, 3, 4, and 6. In Site 1 the pH of lysimeter water samples was ~ 0.5 units lower than that of the STE. In contrast, the pH of lysimeter water samples was ~ 0.5 units higher than that of the STE in Site 5.

Dissolved oxygen. No DO was detected in STE samples on any of the sampling dates.

Reduced iron. Reduced iron (Fe²⁺) was not detected in any of the STE samples (Figure 3). Water from lysimeters between trenches (C2) and downgradient from trenches (C3) had levels of Fe²⁺ that ranged from 1 to 50 mg L^-1, and these values were higher than those observed for upgradient (C1) samples. There were two notable exceptions: Site 1, where C1 samples had a higher concentration of reduced iron than C2 or C3 samples, and Site 5, where no Fe²⁺ was detected in water samples from any of the lysimeters.

Chloride. There were marked differences in the mean Cl^- concentration of STE (Figure 4). Sites 2, 3, 4, and 5 had chloride concentrations varying from 60 to 80 mg L^-1, within the range anticipated for domestic wastewater. In contrast, the Cl^- levels in STE from Sites 1 and 6 were on the order of 300 mg L^-1. The concentration of Cl^- in water from upgradient lysimeters (C1) was on the order of 10 mg Cl^- L^-1 or lower. Site 1 exhibited clear dilution of Cl below the leachfield (apparent removal rates of 89 to 94%, Table 2), with considerably less Cl dilution observed in the leachfield of the other four sites.

Total organic carbon. Mean values of TOC in STE ranged from 90 to 100 mg C L^-1 (Figure 5). There was no apparent trend in the concentration of TOC in lysimeter samples, aside from a generally lower concentration than in STE. Apparent rates of TOC removal were consistently higher than Cl dilution rates in Sites 3, 4, and 6, suggesting that TOC losses were due to processes other than dilution (Table 2). In contrast, Cl dilution rates were generally equal to or higher than apparent TOC removal rates, suggesting that dilution was driving the loss of TOC (Table 2).

Nitrogen. The mean concentration of total N in STE ranged from 35 to 55 mg N L^-1 (Figure 6). Upgradient water samples (C1) had total N levels generally on the order of ~ mg L^-1 except for Site 3, where the mean total N concentration was closer to 10 mg L^-1. Apparent rates of total N removal were consistently highest in Site 1 and lowest in Site 5 (Table 2). However, apparent rates of N removal were consistently higher (27 to 60%) than Cl dilution rates (7 to 17%) only for Site 2 (Table 2), suggesting that N losses at the other sites were mainly due to dilution

Nitrate was not detected in STE from any of the sites (Figure 7). Samples from upgradient (C1) lysimeters in Sites 3, 4 and 5 had mean NO₃ levels between 1 and 3 mg N L^-1, and no nitrate was detected in C1 samples from Sites 1. The concentration of NO₃ in water from C2 and C3 lysimeters was below detection limit for Sites 2 and 4. In contrast, NO₃ levels ranging from 5 to 25 mg N L^-1 were observed in water samples from C2 and C3 lysimeters under the leachfield of Sites 1, 3, 5 and 6.

Ammonium made up the bulk of the total N content in STE, with concentrations ranging from 21 to 33 mg N L^-1 (Figure 8). The lowest NH₄ concentrations were observed in samples from lysimeters in Site 1 (< 3 mg L^-1), and Sites 3 and 4 (< 1 mg L^-1). In contrast, water from lysimeters in Sites 2, 4, and 6 had ammonium concentrations that ranged from 5 to 30 mg L^-1. The presence of ammonium and nitrate in lysimeter water samples was generally mutually exclusive, with ammonium absent or found in very low concentrations where nitrate was present, and nitrate absent or found in very low concentrations where ammonium was present.

Phosphorus. The level of total P in STE ranged from 6 to 13 mg P L^-1 (Figure 9). Upgradient water samples (C1 lysimeters) had total P concentrations on the order of 2 mg P L^-1. Samples from lysimeters between trenches (C2) and downgradient from the trenches (C3) had total P levels that were equal to or higher than those observed in C1 samples. The total P level in lysimeters under the leachfield in Sites 4 and 6 was in a number of instances close to that found in STE inputs. Apparent removal rates for total P were highest at Site 1 and lowest at Site 2 (Table 2). Total P removal rates were higher than Cl dilution rates only for Sites 2 and 6, suggesting that the apparent loss of P in the remaining sites were due mainly to dilution.

Phosphate made up approximately half of the total P content of STE, with concentrations ranging from ~ 2 to 6 mg P L^-1 (Figure 10). The phosphate concentration of water from upgradient wells was generally less than 0.1 mg P L^-1. The level of PO₄ in C2 and C3 lysimeters was also generally less than 0.1 mg P L^-1, with two noteworthy exceptions: at Site 4 the C3 lysimeters had phosphate levels that ranged from 1 to 2 mg P L1, and at Site 6 the C2 and C3 lysimeters had phosphate levels ranging from 2 to nearly 6 mg L^-1. Phosphate made up a negligible fraction of the total P content of samples from lysimeters except at Sites 4 and 6, where it made up nearly 50% of total P.

Sulfate. The level of SO₄ in STE ranged from 9 to 10 mg S L^-1 (Figure 11). There was no consistent pattern to the concentration of SO₄ among lysimeter positions. However, sulfate concentration was generally lower than in STE in lysimeter samples from Sites 2, 4, and 6. In contrast, the level of SO4 in lysimeter samples from Sites 1, 3 and 5 was generally equal to or higher than that in STE inputs.

Fecal coliforms. The number of fecal coliform bacteria in STE samples ranged from 10⁶ to 10⁷ colony forming units 100 mL^-1 (Figure 12). In those instances where samples from upgradient wells (C1) were obtained, the mean number of fecal coliforms ranged from 10¹ to 10² CFU 100 mL^-1. Fecal coliforms were found in wells between leachfield trenches (C2) at levels between 10⁰ and 10² CFU 100 mL^-1 and in downgradient wells (C3) at levels ranging from 10¹ to nearly 10⁵ CFU 100 mL^-1.

Gases. The level of O₂ in gas samples from upgradient (C1) wells ranged from 15 to 20% (Figure 13). Wells installed between leachfield trenches (C2) had levels of O₂ that were generally close to atmospheric levels (21%). The O₂ concentration in downgradient wells (C3) ranged from 5 to 16%.

Carbon dioxide in upgradient wells exhibited a wide range of values, from < 0.1% at Site 6 to 5% at Site 1 (Figure 13), with a similar range of values for C2 and C3 wells.

Methane levels in C1 wells ranged from less than 10¹ ppmv at Site 4 to 10² at Sites 1 and 6 (Figure 14). The concentration of CH₄ in C2 wells ranged from less than 10¹ to > 10⁴ ppmv at Sites 1 and 2, respectively. In C3 wells, the methane concentration ranged from 10¹ to > 10⁴ ppmv.

Hydrogen sulfide was detected only in the C3 wells of Site 4, at a mean concentration of 30 ppmv (Figure 14).

References
APHA, 1998. Standard methods for the examination of water and wastewater, 20th ed., APHA, Washington, DC.

Dissemination
Publications:
Amador, J. A., D. A. Potts, E. L. Patenaude, and J. H. Gorres. 2006. Effects of depth on domestic wastewater renovation in intermittently aerated leachfield mesocosms. ASCE Journal of Hydrologic Engineering (Submitted)

Amador, J. A., D. A. Potts, M. C. Savin, P. Tomlinson, J. H. Görres, and E. L. Nicosia. 2006. Mesocosm-scale evaluation of faunal and microbial communities of aerated and conventional septic system leachfield soils. Journal of Environmental Quality 35:1160-1169.

Workshops: None

Conferences: None

Manuals, Protocols: None

Outreach Activities:. "Cleaning up wastewater with dirt" A 1- hour, hands-on presentation by J. Amador on July 27, 2006 at the Earth Camp, W. Alton Jones Campus, University of Rhode Island, West Greenwich, RI. Approximately 12 campers, ages 11- 14, participated.

Contact with End Users: The End User has been kept informed of the progress of the project.

Patent, Copyright, Invention Disclosure Activity: None

Expenditures
Expenditures are somewhat lower than anticipated for this stage of the project.

End User Advisor Feedback
Name: Brian M. Moore
Organization: RIDEM
Location: 235 Promenade Street, Providence, R.I. 02908
Phone numberL401-222-4700 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.
Renovation of 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)?
No change.

3) Do you see any key challenges that the researchers may want to address or keep in mind?
No. Basic installation issues such as weather and siting constraints.

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

5) Other feedback?
Not at this time.