System Loading. Presentation Outline. Hydraulic Loading - Residential

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1 0 Presentation Outline System Loading Hydraulic & Organic Determination Colorado Design Course March 17 th and 18 th, 2016 Define hydraulic vs. organic loading in accordance with CDPHE Regulation 43 Start with residential systems Discuss commercial systems Evaluate measurement techniques - Flow measurement - Wastewater strength measurement 1 2 Context for Hydraulic and Organic Loading Hydraulic Loading - Residential Typical residential system Why does loading matter? Design requires realistic assumptions about wastewater flow and strength to size the system properly Wastewater quantity: Typically based on number of bedrooms 75 gal per person, 2 people per bedroom This is hydraulic loading Compare these two residences? 3 4 Regulation 43 18% Distribution of mean household daily per capita indoor water use for 1,188 data-logged homes (EPA 2002: Onsite Wastewater Treatment System Manual) 16% 14% 12% Relative Frequency 10% 8% 6% Specific to county regulations - 75 gpd vs. 100 gpd per person - Could be 2 people per bedroom for all bedrooms - Check local regulations 4% 2% 0% Mean Indoor Gallons Per Capita Per Day More 5 6

2 Typical Onsite Wastewater Treatment System Assumptions are made to predict the hydraulic and organic loading a system will receive Wastewater quality affects the capability of the soil to accept effluent, particularity at the infiltrative surface *Reference: Decentralized Water Reclamation Engineering A Curriculum Workbook, Robert Siegrist DRAFT WASTEWATER QUALITY cbod5 Biochemical oxygen demand TSS Total suspended solids FOG Fats, oils & grease 9 10 Organic Loading - Residential Raw Wastewater Research Data Raw Wastewater Regulation 43 CDPHE Regulation 43 assumes an influent BOD5 = 318 mg/l 11 *Reference: Decentralized Water Reclamation Engineering A Curriculum Workbook, Robert Siegrist DRAFT

3 Treated Wastewater Regulation 43 Reg 43 categorizes 5 categories of effluent treatment levels Hydraulic and Organic Loading Calculations Hydraulic Loading Example 3 bedroom single family home 3 bedrooms x 2 people per bedroom x 75 gal per person = 450 gpd Use the LTAR of the soil type to determine the footprint of the soil treatment area Hydraulic and Organic Loading Calculations 15 Mass Loading Example Concentration of constituent in the wastewater Mass (lb) = C (mg/l) x Q (gpd) x ,000,000 Assume 3 bedroom residence with TL1 effluent Q = 450 gpd C = 145 mg/l (per Reg 43) Mass Loading = 0.54 lbs cbod5 per day Other regulations may provide design parameter for lbs cbod5/ft2 16 Commercial Systems Definition of Design Flow Same fundamental rules apply Greater variability in hydraulic and organic loading High strength waste Restaurants, Schools, Churches Collection system (I&I) Cleaning chemicals CDPHE Regulation 22, 22.2, 7: The proposed design capacity shall be the average daily flow at full occupancy CDPHE Regulation 43, 43.6, A.4.a.(2)(i): The daily rate per unit times the number of units at full occupancy shall be the design flow 17 18

4 Example - School Design OWTS for Elementary School with 250 students Regulation 43 = 25 gal/student for school with cafeteria, gym and showers 250 students * 25 gal/student = 7,500 gpd If design flow is greater than 2,000 gpd, Site Application and Discharge Permit are required. Different set of regulations However, data collected for schools in Colorado identifies per capita wastewater generation rates much lower than 25 gal/student Methods to obtain actual flow data If infrastructure is existing, it may be beneficial to obtain actual flow data Could also obtain from similar developments: 1) Potable water use data (consumptive use) 2) ETM, dose counter (account for drain back) 3) Magnetic flow meter (effluent in full pipe) Obtain Real Data on Water Use Potable water use data is often the easiest to obtain The frequency at which the data is collected is important = gal per day Irrigation? Consumptive use? Measuring the Flow of Wastewater Control panels can be specified to include a dose counter and/or an elapsed time meter (ETM) Operator or owner must record data on pre-established frequency (daily, weekly, monthly) Measuring the Flow of Wastewater Magnetic flow meters are highly accurate Depending on controller, may still require daily readings Magnetic flow meters require proper design! Pipe full of liquid Effluent line Obtain Influent Water Quality Data Commercial establishments may have greater variability in influent wastewater constituents Is there a commercial kitchen? Grease trap What is the source? USEPA Class V injection well (car wash) May require advanced treatment 23 24

5 Obtain Influent Water Quality Data Similar to quantifying actual flow values, pulling water quality samples can confirm assumptions. This is important for higher risk sites. Location of influent sample? Potential samples to evaluate: Fats, oils and grease (FOG) less than 25 mg/l in effluent 1 cbod5 145 mg/l see reference note 2 TKN (Total Kjeldahl Nitrogen) mg/l see reference note 2 Commercial Establishments *Reference: Decentralized Water Reclamation Engineering A Curriculum Workbook, Robert Siegrist DRAFT Per Orenco Design Criteria Table A Rev. 11/14 2 Per CDPHE Regulation 43 Table Summary Hydraulic and organic loading needs to be taken into consideration during the design process Reg 43 provides framework for loading values Practical methods are available for documenting actual hydraulic and organic loading Design of commercial systems requires additional investigation and expertise Questions? 27 28