Bruce Lesikar, PhD Texas A & M University University Curriculum Development for Decentralized Wastewater Management

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1 Chapter 3 Drip Emitters and the Soil Bruce Lesikar, PhD Texas A & M University University Curriculum Development for Decentralized Wastewater Management

2 NDWRCDP Disclaimer This work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with funding provided by the U.S. Environmental Protection Agency through a Cooperative Agreement (EPA No. CR ) 0) with Washington University in St. Louis. These materials have not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by representatives of the NDWRCDP. The contents of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S. Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or recommendation for use.

3 CIDWT/University Disclaimer These materials are the collective effort of individuals from academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have been peer-reviewed reviewed and represent the current state of knowledge/science in this field. They were developed through a series of writing and review meetings with the goal of formulating a consensus on the materials presented. These materials do not necessarily reflect the views and policies of University of Arkansas, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.

4 Citation Lesikar, B.J. and J.C. Converse Subsurface Drip Dispersal: Drip Emitters and the Soil - PowerPoint Presentation. in (M.A. Gross and N.E. Deal, eds.) University Curriculum Development for Decentralized Wastewater Management. National Decentralized Water Resources Capacity Development Project. University of Arkansas, Fayetteville, AR.

5 Subsurface Drip Dispersal: Wastewater Treatment Approach Small doses of wastewater into the soil. Uniform distribution over the entire area. Wastewater moves through soil under unsaturated flow conditions, thus effectively treating the wastewater. Wastewater can be dosed into the active surface layer of the soil. Facilitates reuse of nutrients and water.

6 Water Movement - Designing at the Boundaries Water movement from a drip emitter Water movement through the drip field Water leaving the drip field site

7 Soil particle size Soil structure Restrictive layers Soil / Rock Groundwater Controlling Factors Soil Indicators Saturation Biomat Landscape Slope Position

8 Composition of Soil Inorganic materials Organic materials Air Water Microbes Air 25% Organic 2% Minerals 48% Water 25%

9 Hydraulic Loading Rate Textural classification Sand Silt Clay Structure Loading Volume per surface area (gallons per square foot) Trench Infiltrative surface Drip field Footprint area/areal loading

10 Footprint vs. Infiltrative Rates The design infiltration rates can be substituted for footprint loading rates when determining the linear feet of drip tubing needed. Example: The footprint loadings are based on water in the soil. So if a footprint loading for a 2 ft spacing is 0.4 gpd/ft2 each emitter supplies 4 ft2 of footprint area or 1.6 gpd. The infiltrative surface is only around the pipe, which is approximately 0.2 ft2 per foot of pipe and with 2 ft spacing between emitters the infiltrative surface is 0.4 ft2. So, for a 1.6 gpd discharge, the infiltrative surface loading is 4 gpd/ft2

11 Organic Loading Rate Biomat Oxygen transfer capability Loading Mass per surface area (mg per square foot) Mass per emitter (mg per emitter) Trench Infiltrative surface Drip field Surface area

12 Theoretical Hydraulic Acceptance Rates for Soils Receiving Wastewater Sand Loam Silt/Clay Loam Clay

13 Water Movement From A Drip Emitter Saturated Flow Water moving in all directions from the emitter Water moving along the lateral and then out into the soil Unsaturated Flow Dispersal in all directions

14 Modeled Flow Pattern Around a Drip Emitter

15 Biomass Around a Drip Lateral

16 Water Movement From An Operating Drip Emitter min min min 180 min Horizontal distance, cm Horizontal distance, cm Horizontal distance, cm

17 Water and Nutrient Distribution

18 Water Movement Through the Drip Field

19 Water Leaving the Drip Field Site

20 Summary Critical points in water movement Water leaving the emitter Water moving into the soil Water leaving the drip field Where is the water going? How can we manage the water? Emitter and lateral spacing Emitter flow rate Dose volume Dose frequency Cover Crop