Nitrogen Dynamics in Natural Systems Impacts of Onsite ... NITRIFICATION MODEL ¢â‚¬¢Complex ¢â‚¬¢Uses Oxygen

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  • Nitrogen Dynamics in Natural Systems

    Impacts of Onsite Wastewater Treatment and Dispersal Systems / Drip Dispersal

    – Tom W. Ashton

    Environmental Health Specialist

    Professional Soil Scientist

    April 6, 2016

  • Denver, CO

  • Executive Order 13508 of May 12, 2009

    Chesapeake Bay Protection and Restoration

  • Virginia Department of Health, December 2013, Webinar Training, Implementing the Chesapeake Bay Nitrogen Requirements in the AOSS Regulations, Presented by Dr. Marcia J. Degen P.E., Office of Environmental Health Services

  • Phosphorus (Freshwater) & Potassium •No gas phase in cycle

    PLANT and ENVIRONMENTAL NUTRIENTS

    Nitrogen (Salt Water) •Multiple Biologic Pathways

    •Created (Manufactured) / recycled

  • CHES Bay NITROGEN Loadings

    On Site Septic 4%

    AG Related 41%

    Non AG 10%

    Natural 1%!!

    Atmospheric

    Deposition 26%

  • CLASSICAL MODEL

  • •Efficient, closed system, small footprint. Employs fast-growing bacteria, short Mean Cell Residence Time (MCRT

  • Treatment Efficiencies

    Discharge is primarily soluble, mobile NITRATE

  • Wetlands, Soils, and Sediments have many alternative pathways for NITROGEN transformation •Slow Growing Bacteria

    •Extended MCRT (200 days?)

    •“Low fluid shear” environment resulting in stable biofilms

    •Time

    •Size

    •Diversity

    The Classical Theory is no longer valid as a general model with applied to complex natural systems such as sediments, soils, and wetlands.

  • “CLASSICAL”

    DeNite Pathway

    DENITE

    of

    Nitrite

    DENITE

    of Ammonia

  • ANAMMOX •Nitrite and Ammonium to atmospheric Nitrogen

    •Does not require organic Carbon to remove Nitrogen from Wastewater

    •Removal high once biomass is established

    •20% of Oxygen compared to classic Nitrification / denitrification

    Ammonia to N gas by way of ANAMMOX

  • HETEROTROPHIC NITRIFICATION

    MODEL

    •Complex

    •Uses Oxygen and Nitrate simultaneously as terminal electron acceptors favoring aerobic denitrification

    “Dumps” excess ammonia to prevent interference with bacterium energy balance

    Biofilms and “flood and drain” an important element

  • 18

    FIRST VERSION AUGUST, 2013

  • 19 19

    WHAT IS A BEST MANAGEMENT PRACTICE (BMP)?

    ** Basis, design concept as a natural system

    ** Accepted, engineering practice

    ** Specific criteria

    ** Robust / sustainable

    ** Applied and accepted as “deemed to comply”

  • 20 20

    NSF 40 10 / 10

    NSF 245

    Majority of Application #5

    NSF 245

  • 21 21

  • 22 22

    TREATMENT TRAIN COMBINATIONS

    NSF 40 and 10 / 10

    NSF 245

    NSF 245

    Majority of Application NSF 245

    Conventional Gravity Drainfield

  • 23

    3.9 SHALLOW-PLACED PRESSURE-DOSED DISPERSAL

    ** Twelve papers cited.

    ** Seven Papers Specific to Drip Dispersal

    FIRST VERSION AUGUST, 2013

    ** Two additional papers reflect “controlled application” at trench bottom loading rates. Instantaneous dose volume and frequency only achievable in field application with Drip Dispersal.

    Anderson, Otis, Apfel

    (six doses per day, .125-.25 gallons per dose.)

    Duncan, Reneau, Hagedorn (six doses a day, . 083 gallons per dose.)

  • 24 24

    Graphic from “L.D. Hepner Alternative On- Lot Technology Research / Soil Based Treatment Systems (Del-VAL Phase 2)”

    Drip in situ vs. LPD interface

    DRIP PLACES EFFLUENT INTO THE NATURAL SOIL SYSTEM

    NOT ON TO A CONSTRUCTECTED INTERFACE

  • 25 25 Macropores

    Bt Horizon

    Trench bottom

    DRIP DISPERSAL IS NOT A TRENCH

  • 26

    Drip Dispersal Vs. Low Pressure Pipe

    • Direct burial vs. trenches • Area loading (gal./ft.2) equivalent to LPD • Linear loading (gal./ft. of pipe)

    – 10 to 12 times less than LPD • 8 to 10 times more orifices than LPD • Drip Flow 5%-8% per orifice • Total Drip Dose Volume 10% to 20% of LPD

    volume

  • 27

    How Does Drip Treat? THE SOIL TREATMENT UNIT (STU)

    THE Drip “Bio-Reactor”

  • .01 GPM

  • 29

    ** DESIGN Absorption Area footprint by and large equivalent to conventional LPD STE trenches

    ** DESIGN Enhanced tubing “Line Loading” interface for maximum soil contact

    NITROGEN

    Size and Time

    Drip and the “Soil Treatment Unit” (STU) ** Heterogenious biological environment in shallow soils, maximum activity

    ** Free gas exchange (aeration)

    ** Primarily unsaturated conditions provide extended effluent residence time for treatment

  • 30

    How Does Drip Treat? EXCELLENT DISCUSSIONS

    LONG Long, T. 1995. “Methodology to Predict Nitrogen Loading from On-Site Sewage Treatment Systems”. In Proceedings of the Northwest Onsite Wastewater Treatment Short Course, ed, R.W. Seabloom. University of Washington, Department of Civil Engineering, Seattle, Washington, September, 1995.

    NOWRA MODEL CODE Del Mokma, draft report “Soil Treatment of Onsite Wastewater: Basis for Determining Constituent Output for Soil Component Matrices of National Model Code” sponsored by NOWRA National Model Code Subcommittee on Soils, Jerry Tyler, University of Wisconsin and Del Mokma, Michigan State University.

    WALLACE Wallace, Scott 2008 “Emerging Models for Nitrogen Removal in Treatment Wetlands” Scott Wallace P.E, M.S., North American Wetlands”, David Austin, P.E., M.S., Principal Technologist, Natural Treatment Systems, CH2M HILL, Journal of Environmental Health, Volume 71 Number 4, Fall 2008, National Environmental Health Association, Denver, CO.

  • 31 Likely the most exhaustive characterization of the soil treatment unit (STU) to date. 670 total pages.

    DRIP DISPERSAL

    The Soil Treatment Unit (STU)

  • 32

    •Examination of 120 sources with 25 sources containing 85 peer reviewed experiments. For the most part all studies apparently reflected domestic strength STE, single family home application & lab studies. •In many cases the authors had to make educated adjustments and assumptions to fill in missing data in order to generate a data set for analysis. These adjustments were based on an extensive review of the literature. The majority of studies were in Group I, sandy soils.

    TEXTURE

  • 33

    * LAB STUDIES Control on the part on the researcher regarding the amount and method of application as opposed to variable flow and application in situ.

    *FIELD STUDIES Analysis attributed 66% of the variance in N attenuation to Hydraulic Loading Rate (HLR), 20% to depth, 3% to soil textural class, and 11% to the variability within the data itself.

    * For lab studies the soil type was the most important factor, followed by depth, and then followed by HLR . Apparent lesser importance of soil parameters in field studies was attributed to the great variability in soil properties, even within a particular soil type at field sites. These results point to the complexity in which different STU factors impact N treatment.

  • 34

    •Given the variability and scarcity of data collected in field sites, it is unlikely that field data can be used to predict N attenuation for many relevant Onsite Wastewater Treatment Systems (OWTS) and STU operating conditions. Mathematical models are needed that incorporate relevant design variables and operating conditions.

    •HLR may be more important to N treatment within the first 30-60 cm than soil texture and soil depth. Soil depth and soil texture remain important variables. Soil structure may bear out to have a greater effect than soil texture.

    Thus the subsequent document by the same team “Quantitative Tools to Determine the Expected Performance of Wastewater Soil Treatment Units” (WERF. 2010). STUMOD, NCALC, & HYDRUS

  • 35

    “……HYDRUS was modified to account for the effect of water filled porosity, carbon content, and temperature on treatment to improve its ability to simulate nitrogen transformation under a variety of OWTS loading conditions “

    .095 gal/ft2/Day

    .076 gal/emit/Dose

    60+ mg/l total N

  • 36

    •Nitrate removal increased over 66% in a drip field with a relatively low hydraulic loading.

    •In general the model predicts that N applied by drip dispersal greatly influences the soil environment at a depth close to the emitter, but with increasing depth the influence of wastewater nitrogen decreases.

    HYDRUS computer modeling of drip dispersal perfor

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