CEAC Presentation Friday, April 23, 2010

1. CEAC Presentation Friday, April 23, 2010 Chris Crock Aaron Lammers Brent Long Aaron Raak

2. Introduction • Carabuela, Ecuador has a Flawed Wastewater Treatment System • Overloaded Septic Tank • Failed Leaching Field • Worked with HCJB to Remedy the Problem

3. Project Management Client: Bruce Rydbeck Consultant: Tom Newhof Advisor: Leonard DeRooy Team Member: Christopher Crock Team Member: Aaron Lammers Team Member: Brent Long Team Member: Aaron Raak

4. Project Management Group Meeting • Method of Approach • Decision Process • Task Division • Individual • Partner • Team Divide Tasks Individual Research Group Meeting Divide Tasks Individual Design

5. Design Norms/Criteria • Effective Treatment • Culturally Appropriate • Sustainability • Site Appropriate • Low Cost • User Friendliness • Life of Design

6. Requirements • Performance Requirements • Water Effluent • Coliform count < 1000/100 mL • BOD under 2.0 mg/L • Helminth eggs < 1 egg/100mL • (Who standards set E. coli limit for leafy crops at 1,000/100mL; at this level of treatment other pathogens are assumed to be treated as well) • Sludge Effluent • 1000 E. Coli/gram solids • < 1 Helminth egg/ g solids • (With alfalfa, requirements need to only meet Class B sludge treatment. The US EPA determined that sludge which goes through one of six processes of significant reduction of pathogens may be applied to crops)

7. Requirements • Functional Requirements • Handle the waste of the entire population for 20 yrs (2700 ppl. for projected population) • No electricity • The system must fit in 0.5 hectares • No chemical additives • Shall not need experts outside of the village for construction

8. General System Description • Bar Racks • Screen for large solids and objects • Two open channels with inclined bars • Dewatering plate for screenings • Grit Chamber • Settle out large particles (sand, grit, etc.) • Two open channels acting as grit chambers • Velocity control weir • Imhoff Tank • Settle out discrete organic materials and small particles • Store organics for later treatment • Anaerobic digestion of organic solids • Two tanks and settling chambers • Stabilization Lagoons • One facultative pond for BOD reduction • Two maturation ponds for further BOD reduction and pathogen removal • Sludge Drying Beds • Treat sludge from Imhoff Tank and Grit Chamber • Four sludge drying beds for treatment cycling

9. Q = 196 m3/day BOD = 32 kg/day TSS = 40 kg/day General System Description Q = 196 m3/day BOD = 32 kg/day TSS = ? Q = 196 m3/day BOD = 32 kg/day TSS = ? Bar Racks Q = 196 m3/day BOD = 19.6 kg/day TSS = ? Grit Chamber Imhoff Tank Solids = ? Solids = ? Q = 196 m3/day BOD = 0.51 kg/day TSS = ? Sludge Treatment Irrigation Stabilization Ponds

10. Design Decisions/Alternatives – Bar Rack • Bar Racks • Mesh screen fitted to the inlet of grit chamber • Difficult to maintain • Clogs easily • Damages easily • Mesh cage sitting on bottom of channel to catch large objects • Complicated to make • Costly to build • Inclined bars that are manually raked • Easy to maintain • Simple to construct • Fairly cost efficient

11. Environmental Design - Bar Rack • Environmental Design • Important to remove larger solids and particulate • Bar Rack • Design depends mostly on clear space between bars • Velocity should be within 0.3—0.6 m/s • Openings between 20—50 mm • Rack for dewatering screenings • Redundancy accounted for

12. Structural Design - Bar Rack • Structural Design • Bar Rack • Ultimate moment design • Uses minimum steel and cover • Two open channels and racks for redundancy • Two depressed steel plates for dewatering

13. Design Decisions/Alternatives – Grit Chamber • Grit Chamber • Vortex Grit Chamber • Requires electricity • Costly to buy • Modified Vortex Grit Chamber • Not ‘proven technology’ • Does not require electricity • Cheap to make • Old Septic Tank • Cheap to modify • Too large to settle only girt • Difficult to maintain • Rectangular Open Channel • Does not require electricity • Easy to maintain • Requires manual labor • Fairly cheap to construct

14. Environmental Design – Grit Chamber • Environmental Design • Important to remove larger solids and particulate • Grit Chamber • Design largely depends on the velocity the water (0.3 m/s) • Velocity controlled by sutro weir • Grit removed is treated in sludge drying beds • Redundancy accounted for

15. Structural Design – Grit Chamber • Structural Design • Grit Chamber • Ultimate moment design • Uses minimum steel and cover • Two open channels and sutro weirs for redundancy

16. Design Decisions/Alternatives – Imhoff Tank • Septic Tank • Pros - Simple, Durable, Little Space • Cons – Low efficiency, odors, already failed system • Lagoon System • Pros - Simple, Flexible, Little Maintenance • Cons – Large open land, odors, mosquitoes • Imhoff Tank • Pros – Durability, little space, odorless effluent • Cons – Less simple, regular desludging

17. Environmental Design – Imhoff Tank • Environmental Design • Two tanks in one structure for redundancy • Sedimentation • Based off Design guides and rules of thumb • Overflow Rate of 600 gal/ft2 day (Tchobanoglous) • Retention Time of 2 hours (DEWATS) • Clearance, overlap, other recommended dimensions • Digestion • Based on case study of Imhoff tank in Honduras • Sludge storage for 1.87 ft3 per resident (3,370 ft3) • Up to 6 months of sludge storage

18. Structural Design – Imhoff Tank • Structural Design • Analysis of forces and moments in tank • Finite Element Analysis for Sedimentation walls • Structural analysis for primary load bearing walls and beams • Designed steel and concrete to hold for highest loads • ACI 318M-05 –Metric Building Code and Commentary • Minimum reinforcing • Minimum/maximum spacing • Minimum cover • Vertical and horizontal reinforcing based on analysis • Similar to case study tank in Honduras

19. Design Decisions/Alternatives - Lagoons • Facultative Lagoon • Simpler Setup • Less Maintenance • More Land • Less Expensive • Aerated Lagoon • Mechanical aerators to enrich wastewater with oxygen • Better Removal Rates • Less Land • Expensive

20. Environmental Design – Lagoons • Used Kinetics, Temperature Factors, and Hydraulic Residence Times to Size Lagoons • Loading Rates • BOD: 100mg/L • Helminth Eggs: 1000 Eggs/L • E-Coli: 2e7 Coliforms/100mL • Reduced Rates • BOD: 2.7mg/L • Helminth Eggs: 0.10 Eggs/L • E-Coli: 915 Coliforms/100mL

21. Structural Design – Lagoons • Pond System • 1 Facultative Ponds • 2 Maturation Ponds • Dimensions • 21 meters x 21 meters • Depths of 1.5 meters and 0.5 meters • Redundancy

22. Design Decisions/Alternatives – Sludge Treatment • Open sand drying beds • Covered sand drying beds • Drying lagoon • Decision:Open beds • Lower cost • Effective treatment

23. Environmental Design – Sludge Treatment • Must hold sludge for several weeks to dewater • Must hold sludge for longer to make it safe for fertilizer • Designed to hold 1 year’s worth of sludge for Imhoff tank • Area: 960 m2

24. Structural Design – Sludge Treatment • Beds have a layers of sand and gravel • Shear gates to control sludge flow • Low walls of earth or concrete • Underdrain system of PVC pipe

25. Hydraulics • Townspeople connect roof drains to sewers • A large rainfall event could flush the system • Model showed 15x increase in flow during 10-year event • Will require an overflow weir to prevent flushing

26. Hydraulics • Storm inflow: 3100 m3/day • Design inflow: 196 m3/day

27. Grant Proposal • Estimated cost of construction = $25,000 • Probably too much for residents • We are applying to HCJB for a grant to cover the cost of construction • Maintenance costs to be covered by Carabuela • Estimated $14,000/year

28. Questions??