Engineering Design of a Wastewater UV Disinfection System

1. Engineering Design of a Wastewater
UV Disinfection System
Karla Diviesti, Jess Dooley, Nick Tuttle, and Michael Lake
Clemson University, Clemson, SC
December 3, 2019

2. Outline
• Introduction
• Background
• Rationale
• Objective
• Approaches
• Literature Review
• Materials and Methods
• Results
• UV Wastewater Disinfection System
• Upstream Wastewater Components
• Recommendations
• Acknowledgements

3. Introduction

4. Background: Clemson University Wastewater Treatment
Plant (CUWWTP)
● 1.8 - 3.6 MGD current capacity
● Chlorination disinfection systems
○ Chlorine gas and dechlorination
sulfur dioxide
● Growing student population
○ 5000 in next 6 years
● Permits
○ New redundancy requirements
○ Difficult to expand
Student population expectancies

5. CUWWTP Primary Flow Chart
Influent

6. CUWWTP Site Visit

7. ReWa (Greenville, SC) Site Visit

8. ReWa (Greenville, SC) Site Visit

9. Rationale
● Increase student population
○ Projected growth to 26,300 in 2026
● Difficult to meet permit requirements without
downstream expansion
○ Contact time for chlorination
○ Increased level of redundancy required
● Increase safety
○ Adjacent to public walking path
○ Chlorine can be a harmful substance
○ Operator safety
● Decrease operation cost

10. The objective of this project is to engineer and design a UV
wastewater disinfection system to replace the current chlorine
gas based system at the Clemson University Wastewater
Treatment plant (CUWWTP).
Objective

11. Approaches
Task 1: To visit CUWWTP site
Task 2: To evaluate common UV disinfection systems and compare to the existing
chlorine gas system
Task 3: To evaluate E. coli and TSS in influent and effluent samples for both current
chlorine system at CUWWTP and proposed UV system
Task 4: To analyze influent and effluent flow data for an average daily flow and for high
flow events
Task 5: To create models of UV system
Task 6: To research and decide the type of UV lamp to use
Task 7: To investigate upstream components of the plant process
Task 8: To design a final UV disinfection process

12. Project
Disinfection
Technology
Wastewater
Engineering
Environmental Health
Interdisciplinary Connections

13. Literature Review

14. Literature Review Topics
● Methods of wastewater disinfection
● Types of UV lamps
● Types of UV systems
○ Open system
○ Closed system
○ Non-contact system
● Upstream components
○ Floating decanter
○ Sand filter

15. Wastewater Disinfection
Common Types of Disinfection
● Chlorine gas
● Chlorine dioxide
● Ozone
● Ultraviolet (UV) disinfection
Definition: The removal, deactivation, or killing, of pathogenic microorganisms

16. Chlorine Gas
● Chlorine gas and water react to create
hydrochloric acid and hypochlorous
acid (HOCl)
○ Cl2 + H2O HOCl + HCl
● Reaction lowers pH and alkalinity
● Dechlorination is required by sulfur
dioxide
○ SO2 +H2O H2SO3
○ H2SO3 +ClO2 +H2O 5H2SO4 +2HCl

17. Chlorine Dioxide
● Chlorine dioxide attacks the disulfide
bonds in RNA binding proteins
● Kills both inactive and active
organisms
● Difficult to store and transport
○ Onsite manufacturing
● Dechlorination is required
○ Sulfur dioxide
○ Sulfite salts

18. Ozone
● Ozone (O3) reacts with water to form
hydroxyl radicals (OH-1)
● The cell lyses and dies on interaction
with both ozone and hydroxyl radicals
● No regrowth of microorganisms
● Corrosive, requires corrosion-resistant
material
● Unwanted by-products
○ aldehydes, various acids, and aldo- and
keto-acids

19. Disinfection Kinetics: Chemical Treatment
● Chick-Watson Model
● Rennecker-Marinas Model
● Collins-Selleck Model

20. Ultraviolet Disinfection
● Non oxidizing process
● Disrupts DNA to inactivate
microorganisms
● Germicidal range: 200 nm - 300 nm
● Parameters for effectiveness
○ Chemicals present in wastewater
○ Total Suspended Solids (TSS) levels
○ Microorganisms present
○ Physical characteristics of UV system
● No harmful chemical byproducts
● Works against algae growth

21. Ultraviolet Disinfection
● UV light can also damage human DNA
● Water turbidity
● TSS concentration
● Microorganism reactivation
○ Repair damage done by UV exposure
○ Photoreactivation
○ Dark repair (nucleotide excision repair)

22. Disinfection Kinetics: UV Treatment
● UV disinfection - Modified Chick Watson
● UV Inhibition
○ Beer-Lambert Law

23. Types of UV Lamps
● Low pressure low intensity
○ UV-C (shortwave) ~ 254 nm
○ 80-85% monochromatic output
○ Optimal temperature (40℃) must be maintained
● Low pressure high intensity
○ Mercury-indium amalgam
○ More stability over wider temperature range
○ 2 to 10 times greater output than the low intensity lamps
● Medium pressure high intensity
○ Extremely high operation temperatures (600℃ - 800℃)
○ Between 20 to 50 times total UV-C output of low pressure low intensity
○ Efficiency issues, only 15-20% emission is within germicidal range
○ Large facilities limited space

24. UV System: Open System
● Low pressure, low or high intensity UV lamps
● Lamps are submerged parallel, perpendicular, or inclined
○ Inclined lamps can be longer with higher output
● Depth of flow needs to be maintained
○ Short circuiting
● Frequent cleaning of quartz sleeves
● Safety concerns
○ UV exposure during maintenance

25. UV System: Closed System
● Low or medium pressure, high
intensity UV lamps
● Can run both perpendicular and
parallel
● More complex hydraulics

26. UV System: Non Contact System
● UV lamps are not submerged in water
● Can be open or closed
● Can eliminate need for sleeves around
lamps
● Easier replacing/repairing of lamps
● Non-amalgam based lamps can be used
○ Low pressure low intensity
UV Lamp
Sleeve with water flow

27. Upstream Components:
Floating Decanter
● Remove water from the top of SBR
● Prevents sediment (TSS) in downstream processes

28. Cloth Disk Filter (CDF)
● Random weave membrane
● Several stacked flat, grooved discs
● Thickness depends on the influent flow
and desired effluent quality
● Requires backwashing for filter
cleaning
● Proven effectiveness for TSS removal

29. Upstream Components: Sand Filter
● Slow and rapid sand filtration
● Layered with sand and supporting
gravel
● Schmutzdecke or the “dirty layer”
○ Biological filtration layer
○ Slow sand filters only
● Better TSS removal
● Backwashing required to remove solids
and clean the filter
Effluent
Influent

30. Downstream Components: Flow Regulation
● Weir
○ Controls the depth within a channel
○ UV lamps must remain submerged at all
times
● Gate
○ Require mechanical operations

31. Materials and Methods

32. Materials and Methods
● Meetings with potential UV vendors
○ Enaqua and Trojan
● Site visits to current UV operating plants
○ ReWa
● Model of current infrastructure
○ SuperPro and Fusion
● Model of proposed UV installment
○ SuperPro and Fusion
○ Upstream component calculations
○ TSS
● Model of disinfection kinetics
○ Stella
● Cost analysis

33. Wastewater Quantity and Frequency
Current Flow Data

34. CUWWTP Wastewater Treatment/Quality and
Disinfection
● Chlorine process model – SuperPro
○ TSS evaluation
● SBR, secondary clarifier, chlorination, and dechlorination

35. Current Operating Cost
Chlorine
● 54 canisters
● $282.66/canister
Total: $15,263.64
Sulfur Dioxide Maintenance
Average Operating and Maintenance Cost per Year
● 38 canisters
● $107.45/canister
Total: $4,083.10
● Inspection and
annual repair
Total: $5,000.00
Total: $24,346.74

36. Recap UV vs. Chlorine Disinfection
● Non-chemical process
● No toxic byproducts introduced to the
environment
● Inactivates most bacteria, viruses, and
spores
● Equipment requires minimal space
● Low dosages may not effectively
inactivate microorganisms
● Effectiveness dependent on water
turbidity and TSS
● Dosing rates are flexible
● Effective against broad spectrum of
pathogens
● Requires chemicals for chlorination
and dechlorination
● Storage and handling of toxic
materials
● Byproducts are toxic to environment
UV Disinfection Chlorine Gas Disinfection

37. Why UV Disinfection?
● Effective at inactivating most microorganisms,
viruses, and spores
● Shorter contact time relative to other methods
● Eliminates the need to handle and store
toxic/dangerous chemicals
● No chemical byproducts harmful to humans or the
ecosystem
● Equipment requires less space than other methods
● Operator friendly

38. Design Inputs

39. Proposed System - Enaqua

40. Proposed System - Enaqua

41. Proposed System - Enaqua

42. Proposed System - Enaqua Front View

43. Proposed System - Enaqua Top View

44. Proposed System - Enaqua Inlet and Outlet View

45. Enaqua Initial Cost
$438,725.00

46. Enaqua Yearly Operating Cost
Lamps
● 41 lamps per year
● $100.00/lamp
Total: $4,100.00
Average Power Draw
Operating and Maintenance Cost per Year
● 0.117 $/kWh
● 207.84 kWh/day
Total: $8,875.81
$12,975.81

47. Possible Additional Maintenance - Enaqua
● Reactor cleaning 1-2 times per year
○ 5-10 total man hours
○ Clemson University facilities

48. Proposed System - TrojanUV

49. Proposed System - TrojanUV

50. Sample TrojanUV3000plus System - Texas

51. Proposed System - TrojanUV

52. TrojanUV Initial Cost
Total cost: $607,080.00
+ INSTALLATION

53. TrojanUV Yearly Operating Cost
Lamps
● 24 lamps per year
● $332.00/lamp
Total: $7,968.00
Average Power Draw Maximum Power
Draw
Operating and Maintenance Cost per Year
● 8760 Hour
● Power draw: 6.5 kW
● 0.117 $/kWh
Total: $6,701.84
● 8760 Hour
● Power draw: 16 kW
● 0.117 $/kW/h
Total: $16,496.83
Average: $14,669.84 Max:
$24,464.83

54. Possible Additional Maintenance
● Ballast replacement
○ 5 year warranty
○ $800 per ballast
○ 2% failure rate
● Acticlean Gel replacement
○ 2⨉ a year
○ $70 per year
● Wiper seal replacement
○ 2-3 years
○ $10 per module
○ 16 modules
○ $160 total

55. Results

56. CUWWTP Design Process- SuperPro
Chlorine process model – SuperPro

57. Current System Model- Fusion 360

58. Current System Model- Fusion 360

59. Pathogen Reduction Chlorine - Stella Model
● Chick-Watson Model
○ 15 mg/L Dose

60. Stella Model Results
● Contact Time 15-40 minutes
○ Log-5 reduction of E. coli

61. CUWWTP Design Process- SuperPro
Chlorine Process Design

62. UV Process Design Options- SuperPro
UV Process Design - with filter
UV Process Design - without filter

63. TSS Results - SuperPro
Current Disinfection
System
Designed Disinfection
System with filter
Designed Disinfection
System without filter
TSS Concentration
(mg/L)
TSS Concentration
(mg/L)
TSS Concentration
(mg/L)
Influent 170 170 170
Effluent 30 6 19
Input TSS Removal for
Operation
Input TSS Removal
for Operation
Input TSS Removal
for Operation
Floating Decanter N/A 75% 75%
Decanter 60% N/A N/A
Secondary Clarifier 55% 55% 55%
Filter N/A 70% N/A

64. Enaqua Model- Fusion 360
area for expansion

65. TrojanUV Model - Fusion 360
area for expansion

66. Pathogen Reduction UV - Stella Model
● Modified Chick-Watson Model
○ Dose of 40 mJ/cm^2

67. Stella Results
● Contact time 50-120 seconds
○ Log-5 reduction of E. coli

68. Alternative Designs Cost Comparison
f
TrojanUV Enaqua
● Channels, modules, power and
control panels
● Miscellaneous equipment
● Startup and commission
● UV reactor, power panels and
control panels
● Startup and commission
● Spare parts
Total: $607,080.00 Total: $438,725.00

69. Yearly Operating Cost Comparison
Current System Enaqua TrojanUV
● Chemical purchasing
● Maintenance
● Power usage
● Lamp replacement
● Power usage
● Lamp replacement
$24,346.74 $12,975.81 $14,669.84

70. Recommendations
● We recommend that an Enaqua non-contact
UV disinfection system be installed at the
CUWWTP
○ Roughly 50% reduction in operation cost
○ Increase operator and public safety
○ Easy expansion
○ Exceeds permit requirements
● In addition to the new system, we
recommend installing an upstream floating
decanter in the SBR
○ Increase TSS removal
○ If floating decanter becomes insufficient, add
choice of filter

71. Recommended Design
Initial Cost $438,725.00
Annual Operating
Cost
$12,975.81

72. Project Disinfection
Technology
Wastewater
Engineering
Environmental Health

73. Acknowledgements
We would like to thank the following people for their insights and contributions to this
project.
● Dr. Christophe Darnault and Ms. Jazmine Taylor
● Matt Garrison and the CUWWTP staff
● Gary Hunter and Black & Veatch Team
● Steve Squires (Enaqua)
● Michael Shortt (TrojanUV)
● Dr. Alessandro Franchi (AECOM)
● Bryan Kohert (ReWa)

74. Thank you!