Time dose vs. Pump & Dump - Mike Schwartz
Download as PPT, PDF1 like2,585 views
1. A time dosed system distributes effluent through small diameter pressurized laterals with orifices, while a "pump and dump" system uses larger non-pressurized laterals. 2. Key components of a time dosed system include a septic tank, dosing tank, pump, disposal area of small diameter laterals with orifices, and a programmable timer to control pump cycles. 3. Design of a time dosed system involves calculating orifice spacing and size, lateral diameter, pump size, dose volume, run time, and number of doses per day to ensure uniform distribution without overloading the soil.
Time dose vs. Pump & Dump - Mike Schwartz
- 1. Michael A. Schwartz, P.E. Time Dose vs. “Pump & Dump”
- 2. This is what we want to avoid, right!?
- 3. So here’s what we’ll learn about: Basic System Layout Operations Major Components of Each System •Identify differences for each system •Design criteria (engineering standpoint) •Examples Field Example - Conversion
- 4. Background • Major Components of a Traditional Gravity System • Septic Tank • Drain field (Disposal Area) • Distribution Box
- 5. Background • Major Components of a Pump System • Septic Tank • Pump • Dose Chamber • Drainfield (Disposal Area)
- 6. Types of Pump Systems
- 7. “Pump & Dump” • Septic Tank • Raised or at Grade • Dosing Chamber • Traditional Trench or Bed • Pump • Containing 4” PVC Diameter • Conventional Disposal Area Laterals (Non-pressurized) Types
- 8. Time Dose • Septic Tank • Traditional Trench or Bed • Dosing Tank • Containing Small Diameter • Pump Laterals (1”-2”) • Conventional Disposal Area • Lateral with Orifices (small holes) • Raised or at Grade • Pressurized System Types
- 9. Typical Trench Cross-Section Types
- 10. Float Operation Comparison “Pump & Dump” Time Dose • Float 1 – High Water • Float 1 – Lag Pump – Alarm Timer Over-Ride (HWA) • Float 2 – Lag Pump On • Float 2 – Lead Pump - • Float 3 – Lead Pump On Timer Over-Ride (HWA) • Float 4 – Pumps Off • Float 3 – Pumps Off / • Float 5 – Redundant Timer Enable Off / Low level Alarm • Float 4 – Redundant Off / Low level Alarm
- 11. Major Components
- 12. Septic Tank • Remains the same size for the 3 systems • Traditional Gravity • Pump & Dump • Time Dose Septic Tank • Sizing is currently based on hold time Major Components Dosing Tank • 24-hours or 72-hours (food service) • Exception (minimal size –typically 1,000 Pump gals) Disposal Area • Purpose – Pretreatment (separate - solids, FOG, liquid) Major Components
- 13. Septic Tank • Example #1 • 2,400 gallons per day • Non-Food Service Establishment • Loamy Sand Septic Tank • Typically perform topographic and Dosing Tank boundary survey, soils evaluation and flow determination to determine constraints Pump • Septic Tank Size = 24-hour flow • Therefore minimum tank size = 2,400 Disposal Area gallons Major Components
- 14. Major Components “Pump & Dump”: Dose Tank & Pump
- 15. “Pump & Dump” • Sizing • Dosing Chamber • The liquid capacity of the dosing tank must be sufficient to dose the soil absorption Septic Tank field or bed no more than three (3) to four (4) times a day at design flow. Dosing Tank • Pump • Pumps should be sized to empty the dosing Pump tank in no more than 20 minutes. • Automatic alternating pumps shall be Disposal Area provided in all systems where design flow exceeds 2,000 gallons/day and in locations where continuous reliability is essential. Major Components
- 16. “Pump & Dump” • Example #2 • 2,400 gallons per day • Non-Food Service Establishment • Loamy Sand Septic Tank • Since Flow > 2,000 gallons per day, design Dosing Tank system with 2 pumps Pump Disposal Area Major Components
- 17. “Pump & Dump” • Example #3 • 2 Pumps to 1 Disposal Area • Dose Chamber = 2,400 / 3 = 800 gal • Dose Chamber = 2,400 / 4 = 600 gal Septic Tank • Dosing Tank Size = 1,000 gallon – 1,200 Dosing Tank gallon Pump Disposal Area Major Components
- 18. “Pump & Dump” • Example #4 • 2 Pumps to ½ of the disposal area each • Dose Chamber = 2,400 / 6 = 400 gal • Dose Chamber = 2,400 / 8 = 300 gal Septic Tank • Dosing Tank Size about 500-750 gallon Dosing Tank Pump Disposal Area Major Components
- 19. “Pump & Dump” • Example #5 • Pumps should be sized to empty the dosing tank in no more than 20 minutes. • 300 gallons / 20 minutes = 15 gpm Septic Tank (minimum) • Pumps need 2 items to specify Dosing Tank • GPM Pump • TDH (Total Dynamic Head) • TDH = Static Lift + Friction Lost Disposal Area • Friction Loss also known as “head lost” is divided into two main categories, "major losses" associated with energy loss per length of pipe, and "minor losses" associated with bends, fittings, valves, etc. Major Components
- 20. Major Components “Pump & Dump”: Disposal Area
- 21. “Pump & Dump” • Disposal Area Sizing • Absorption systems shall be sized on the basis of the maximum daily sewage flows, according to the following table: Septic Tank Dosing Tank Pump Disposal Area Major Components
- 22. “Pump & Dump” • Example #6 • 2,400 gallons/day • Non-Food Service Establishment • Loamy Sand Septic Tank • Assuming a trench layout: Dosing Tank • Loamy Sand = 0.75 gal per day / square foot Pump • 2,400 g.p.d. / 0.75 g.p.d./sq.ft. = 3,200 sq. ft. Disposal Area Major Components
- 23. “Pump & Dump” • Example #7 – Network Layout • 3,200 sq. ft. bottom area required • Assume trench is 3’ wide: 3,200 / 3’ = 1,070 LF of trench required Septic Tank • Probably use 12 trenches that are 90 feet long x 3’ wide with 4’ undisturbed earth Dosing Tank between trenches. Pump • With 2 pumps, each pump would discharge to 6 of the 12 trenches. Disposal Area Major Components
- 24. Time Dose
- 25. Time Dose • Septic Tank • Traditional Trench or Bed • Dosing Tank • Containing Small Diameter • Pump Laterals (1”-2”) • Conventional Disposal Area • Lateral with Orifices (small holes) • Raised or at Grade • Pressurized System Major Components
- 26. Time Dose • Why Time Dose? • Pressure distribution is a recent modification to the conventional dosed sewage system. Uniform distribution over the bottom area of the drain field is achieved and provides certain advantages over conventional systems as follows: 1. Formation of the clogging mat is substantially delayed. 2. System provides for unsaturated flow into underlying soil. 3. System design is not limited to rectangular configuration. Major Components
- 27. Time Dose • Why Time Dose? Same Different Septic Tank x Conventional Disposal Area x Raised or at Grade x Traditional Trench or Bed x Containing Small Diameter Laterals (1”-2”) x Lateral with Orifices (small holes) x Pump x Dosing Tank x Major Components
- 28. Time Dose • Order of Design • Septic Tank – Same (based on retention time) • Disposal Area Network • Orifices (small holes) – Spacing & Size • Laterals Diameter • Pump • Dosing Tank Major Components
- 29. Major Components Time Dose: Disposal Area
- 30. Time Dose 1. Configure Disposal Area Network 2. Determine Length of Lateral • Example: 2,400 gallons per day, Non-Food Service Establishment, Loamy Sand Septic Tank • Assuming a trench layout: • Loamy Sand = 0.75 gal per day / sq. foot Disposal Area • 2,400 g.p.d. / 0.75 g.p.d./sq.ft. = 3,200 sq. Pump ft. • Assume trench is 3’ wide: Dosing Tank • 3,200 / 3’ = 1070 LF of trench required • Use 12 trenches that are 90 feet long x 3’ wide with 4’ undisturbed earth between trenches Major Components
- 31. Time Dose 3. Determine “orifice” spacing and size • Michigan Criteria for Subsurface Sewage Disposal reference “Pressure Distribution Network Design Manual,” Technical Guide for Pressure Mound Systems (June 2003 MDEQ) • Pressure distribution system design should generally comply with Septic Tank currently accepted design practice including the following features: • Design shall provide uniform doses with no more than 0.5 gallons per orifice per dose. Disposal Area • Distribution cell area per orifice shall not exceed 12 sq.ft. • To reduce orifice plugging, high head pumps are recommended. Pump • Orifice shields should be provided. • Provisions for flushing must be incorporated at the ends of all laterals. Dosing Tank • Geotextile fabric which prevents the downward migration of fine materials but allows for free passage of air and water should be placed over the stone in the distribution cell prior to placement of final cover. Major Components
- 32. Time Dose 3. Determine “orifice” spacing and size • Distribution cell area per orifice shall not exceed 12 sq.ft. • Spacing is typically 3-5 feet apart (some Septic Tank health department code books dictate spacing. Disposal Area • If the trench is 3’ wide and each orifice is to “distribute” effluent to 12 sq.ft. than Pump spacing is 4’ apart Dosing Tank Major Components
- 33. Time Dose 3. Determine “orifice” spacing and size • Orifice sizes can range from 1/8” diameter to 5/8” diameter. • Typically 1/8”, 3/16” or 1/4” diameter Septic Tank • 3/16” diameter is most common sized used Disposal Area • Larger holes will be problematic on finding Pump a pump to produce adequate design flow • Some health departments provides Dosing Tank recommended size • Ultimately up to the design engineer Major Components
- 34. Time Dose 4. Determine lateral pipe diameter Septic Tank Disposal Area Pump Dosing Tank Want the 1st orifice to distribute approximately equal to the last orifice (this table is for 3/16” orifices) Major Components
- 35. Time Dose 5. Determine Number of Orifices/Lateral • # of orifices = Length of Lateral / Spacing of orifice • Example: 90 ft lateral / 4 ft spacing = 23 Septic Tank orifices Disposal Area Pump Dosing Tank Major Components
- 36. Major Components Time Dose: Pump
- 37. Time Dose 6. Determine Lateral Discharge Rate Septic Tank Disposal Area Pump Dosing Tank If 3/16” orifice with 4 ft pressure = 0.83 gal/orifice 23 orifice / lateral x 0.83 gal/orifice = 19.09 gal/lateral Major Components
- 38. Time Dose 7. Determine Network Discharge Rate (zone) • Determine how many laterals are in the network (per pump or zone) and multiple by GPM per lateral Septic Tank • 12 trenches (laterals) with each pump utilizing 6 laterals each (network has 2 Disposal Area zones) • 6 laterals x 19.09 gal / lateral = 114.5 gpm Pump • This is the minimum pump flow required Dosing Tank Major Components
- 39. Time Dose • Pump Comparison Sizing • Pump & Dump” • 20 minutes to empty septic tank • Time Dose Septic Tank • # of orifices (more orifices = more gpm) • Size of Orifices (larger orifices = more gpm) Disposal Area • Spacing of orifices (closer space = more Pump gpm) • Example: 15 gpm vs. 114.5 (6 – 90’ Dosing Tank trenches per pump) • Each on is dosing 1,600 sq ft of area • “Pump & Dump” = 20 minutes • Time Dose = very short timeframe Major Components
- 40. Time Dose 8. Calculate Manifold Size 9. Determine the Total Dynamic Head • TDH = Static Lift + Friction Lost + Perforation Head Septic Tank • Perforation head = 1.3(Q/(11.79*d^2))^2 Disposal Area • Perforation head = 1.3(squirt height) 10. Select Pump Pump • Pumps need 2 items to specify (GPM & Dosing Tank TDH) • Repeat if necessary Major Components
- 41. Major Components: Time Dose Pump Curve
- 42. Major Components Time Dose: Dose Chamber
- 43. Time Dose 11. Determine Dose Volume • Technical Guide for Pressure Mound Systems (June 2003 MDEQ) • Design shall provide uniform doses with no Septic Tank more than 0.5 gallons per orifice per dose. • Example: 6 laterals with 23 orifices per Disposal Area lateral = 138 orifices • 138 orifices x 0.5 gal per orifice dose rate = Pump 69 gals per dose Dosing Tank Major Components
- 44. Time Dose 12. Calculate Run Time of Pump • Run Time = (Dose Volume + “Empty” Pipe Volume) / Pump Rate • Example: Septic Tank • Dose Volume = 69 gallons • Volume to “fill” pipe = 17 gallons Disposal Area • Pump Rate = 114.5 gpm Pump • Run Time = (69 gal +17 gal) / 114.5 gpm = 0.75 minutes = 45 seconds Dosing Tank Major Components
- 45. Time Dose 13. Calculate Number of Doses/Day • Gallons per day = 2,400 • Gallons per dose = 69 • Doses per day = 2400 / 69 = 34 doses Septic Tank • Therefore each pump will operate 17 Disposal Area times per day Pump Dosing Tank Major Components
- 46. Time Dose • Calculation Check • Dose = 0.5 gallons / dose / orifice • # of doses per day = 17 • Gallons per day / orifice = 8.5 gallons Septic Tank • Soil Load Rate 0.75 gal/sq. ft. Disposal Area • Each orifice is dosing 12 sq. ft. • Dose < 0.75 gal/sq. ft. x 12 sq. ft. = 9 Pump gallons Dosing Tank • Numbers check Major Components
- 47. Time Dose 14. Calculate Programmable Timer Settings • Previous step determined number times a pump turns on (34 times) • If want to equal dose over 22 hours Septic Tank (account for peak days) • Duration is up to the design engineer Disposal Area • 22 hours x 60 min/hour = 1320 minutes Pump • 1320 minutes / 34 times = 38.8 minutes • Therefore a pump will run 45 seconds and Dosing Tank no pump will run for 38 minutes • (76 minutes off time per pump) Major Components
- 48. Time Dose 15. Size the Dose Chamber • Up to the judgment of the engineer • Based on off time and timing of incoming flow Septic Tank Disposal Area Pump Dosing Tank Major Components
- 50. • Conversion of a “Pump & Dump” to a Time Dose System • Flushing Elementary, Flushing, MI System Conversion
- 51. Existing Drain Field System Conversion
- 52. Drawing System Conversion
- 53. Existing Septic Tank /Pump Chamber System Conversion
- 54. Existing Septic Tank /Pump Chamber System Conversion
- 55. Existing Septic Tank /Pump Chamber System Conversion
- 56. Existing Septic Tank /Pump Chamber System Conversion
- 57. Proposed Drain Field System Conversion
- 61. Construction System Conversion
- 62. Construction System Conversion
- 65. Construction System Conversion
- 66. Construction System Conversion
- 69. Construction System Conversion
- 70. Construction System Conversion
- 71. Construction System Conversion
- 72. Construction System Conversion
- 73. Final Site Photos System Conversion
- 74. Final Site Photos System Conversion
- 75. Thank you. Do You Have Questions? E-mail Mike: Michael A. Schwartz, P.E. mschwartz@preinnewhof.com
Editor's Notes
- #7: “ Pump & Dump” and Time Dose Pressure system vs gravity to last orifice