Transcript Stage 1 D/DBP Requirements

PLANT OPTIMIZATION AT NORTH
TABLE MOUNTAIN WATER AND
SANITATION DISTRICT
Presented By:
Rick Jeschke P.E.
District Engineer/Manager
NTMW&SD Background
 District formed in November 1958
 Publicly owned
 Run by an elected 5 member Board
 3200 service connections
 Serves a population > 10,000
NTMW&SD Water Plant
 Originally constructed in 1962
 Major upgrades
• 1985 pump station
• 1986 new filters
• 1997 Actiflo ballasted floc system
• 1999 MIOX chlorination system
• 2001 new filters
NTMW&SD Water Plant
 Surface water plant
 Plant rated at 15 MGD
 Yearly output 650 to 700 MG
 Actiflo ballasted floc treatment
 MIOX on-site chlorination system
 8 multi media filters
Stage 1 D/DBP Requirements
 Prompted by the EPA December 1998
 TTHM MCL was set at 0.080 mg/L
 HAA5 MCL was set at 0.060 mg/L
 Chlorite MCL was set at 1.0 mg/L
 Bromate MCL was set at 0.010 mg/L
 Systems with a population over 10,000 had
to be in compliance by January 1, 2004
NTMW&SD DBP
 In 1997 NTMW&SD average DBP were
• TTHM 0.063 mg/L
• HAA5’s 0.0404 mg/L
• Chlorite and Bromate were below DL
 The District felt that these values were to
close to the MCL so plant upgrades were
proposed
DBP Treatment Methods
 Oxidation
• Ozone
• Chlorine dioxide
• UV
 Aeration
 Activated carbon
 Synthetic resins
 Remove precursors
Actiflo Ballasted Floc Process
 Coagulated with alum
 Microsand and polymer are added next
 Destabilized suspended solids bind to the
microsand through polymer bridges
 Maturation to form micro sand ballasted
floc
 Sludge/microsand sent to hydrocyclones to
separate the microsand from the sludge
Actiflo Flow Schematic
NTMW&SD Actiflo Plant
 Construction started Sept. 1997
 Online May 1998
 Two 7.5 MGD trains
 Each train 19 feet by 48 feet
 Total max detention time 21 minutes
 Total max settling time 10 minutes
 Designed for 24 GPM/ft squared
Actiflo TTHM Reduction
 Pre Actiflo TTHM levels 0.063 mg/L
 Post Actiflo TTHM levels 0.041 mg/L
 TTHM levels reduced by 35%
Actiflo HAA5 Reduction
 Pre Actiflo HAA5 levels 0.040 mg/L
 Post Actiflo HAA5 levels 0.028 mg/L
 HAA5’s levels reduced by 31%
Actiflo Microscopic Particulate
Analysis (MPA) Reduction
 Pre Actiflo 3 to 4 log removal
 Post Actiflo 4 to 5.5 log removal before
filtration
 Post Actiflo 6 to 6.7 log removal after
filtration
Clarified Turbidity
CLARIFIED NTU
7
CO NVENTIO NAL
4
3
ACTIFLO
2
1
0
June
July
Aug
Sept
O ct
Nov
Dec
Jan
Feb
March
April
May
NTU
6
5
MONTH
Filtered Turbidity
FILTERED NTU
0.09
NTU
0.08
CO NVENTIONAL
0.07
ACTIFLO
0.06
0.05
0.04
June Aug O ct Dec Feb April
July Sept Nov Jan March May
MONTH
Standard Plate Count (SPC)
 Raw water SPC are 5/mL to 200/mL
 Clarified SPC are 2/mL to 16/mL
 Recycling sand not contributing to SPC
Sand Carryover
 During initial startup some sand carry over
was observed
 After three days no sand carry over was
observed
 Sand carryover filtered out easily
Sand Consumption
 Hydrocyclones are not 100% efficient
 Sand loss is approximately 4 pounds per
million gallons produced
 Equates to $0.40/MG
 Sand purchased 12 tons at a time
 Sand costs $0.10/pound delivered
Sand Abrasion
 Online since May 1998
 Six years of operation
 No wear on SS pipe
 No wear on hydrocyclones
 After six years lead pump liners were
replaced
MIOX at NTMW&SD
 Before MIOX the District used chlorine gas
 Safety was the main factor in the decision to
go to on-site generation.
 On-site generation eliminated the storage
space for bleach
 On-site generation meant that the chlorine
would only be made when needed (with the
system fully automated)
MIOX On-Site Chlorine Production
 Electrolysis of salt water to
generate chlorine practiced
commercially for > 100
years
 Chlorine produced at large
chlor-alkali plants, packaged,
and sold
 Chlorine gas cylinders
 Sodium hypochlorite drums
 Calcium hypochlorite tablets
 Within past 30 years, developed smaller equipment to
generate sodium hypochlorite on-site by same process
 On-site generation uses only salt, water, and electricity
 Eliminates hazardous chemicals
 Heart of technology is the electrolytic cell
How the Cell Works
 Brine -- NaCl dissolved in H2O
 Positive ions are drawn to the
cathode; negative ions are drawn to
the anode
 Apply power
 Possible electrolytic reactions
Anode:
2 Cl- ==> Cl2 + 2eHOCl + H2O ==> ClO2 + 3H+ + 3e2H2O ==> O2 + 4H+ + 4eO2 + H2O ==> O3 + 2H+ + 2eCathode:
2H2O + 2e- ==> H2  + 2OHHydrolysis in Bulk:
Cl2 + H2O ==> HOCl + Cl- + H+
MIOX On-Site Chlorine
Generation System
DC POWER
SUPPLY
On-Site Chlorine Generation
Advantages
 Safety
• No hazardous chemicals used, generated
stored, or transported
• Chlorine concentration approx. 0.37-0.40%
• No potential for chlorine leak
• No possibility of forming chlorine gas
cloud by mixing with water
• No combustible combinations
On-Site Generation Advantages
(continued)
 Regulatory Ease
• No RMP
• No HAZMAT training
• No SCBA equipment
• No “two man rule” for changing out cylinders
• No chlorine scrubber, as required by Uniform
Fire Code
• No DOT trucking requirements
• No corrosion due to chlorine off-gassing
On-Site Generation Advantages
(continued)
 Cost Savings
• Operating costs depend on cost of salt and
power
• Cost of power offset by not purchasing chlorine
• Lower than bleach or calcium hypochlorite
• Lower than ozone, UV, or ClO2
• Lower liability
On-Site Generation Advantages
(continued)
 Freshness and Consistency of Solution
• Generated on-site as need
• Shelf-life is a non-issue
• No need to change dilution or mixing ratios
• No degradation to chlorite or chlorate on shelf
MIOX at NTMW&SD
 Three 50 pound per day cells
 One 100 pound per day cell
 Bulk salt storage
 Storage capacity of up to 600 gallons of
MIOX solution
MIOX TTHM Reduction
 With the Actiflo system reducing the TTHM
by 35%, no further improvement was
expected using MIOX
 Pre-MIOX TTHM levels 0.041 mg/L
 Post-MIOX TTHM levels 0.023 mg/L
 TTHM levels reduced by 44%
MIOX HAA5’s Reduction
 With the Actiflo system reducing the
HAA5’s by 35%, no further improvement
was expected using MIOX
 Pre-MIOX HAA5 levels 0.028 mg/L
 Post-MIOX HAA5 levels 0.016 mg/L
 HAA5’s levels reduced by 43%
NTMW&SD Chlorine Dosage
 District policy is to maintain a minimum
0.4 mg/L residual in the distribution system
 Pre-MIOX residual leaving the plant was
1.1 mg/L
 Post-MIOX residual leaving the plant
0.8 mg/L
 Chlorine dosage reduced by 27%
NTMW&SD Lime Dosage
 MIOX is near pH neutral
 Chlorine gas has a low pH
 Post-MIOX the lime dosage reduced by
50%
MIOX System Maintenance
 Amps and volts checked daily
 Pressure at cell checked daily
 Combined chlorine concentration checked
daily
 Individual MIOX cell concentration
checked monthly
 Hardness checked weekly
MIOX System Maintenance
(continued)
 Orifices are checked for blockages weekly
 Flows through the cells are checked twice
per month
 Cartridges Filters are changed out twice per
year
Control Panel
MIOX Cell Acid Cleaning
 MIOX cells are acid cleaned twice per year
 Cleaned with a 50/50 HCl solution
 Allowed to sit for 15 minutes
 Rinsed with softened water
 Entire process takes approximately 1 hour
Miscellaneous MIOX Information
 Important to buy highest quality salt
 Salt received in 25 ton bulk shipments
 25 tons of salt costs $1,600 including
delivery
 MIOX provided a list of recommended
spare parts
Total TTHM Reduction
 Pre-Actiflo and pre-MIOX TTHM levels
0.063 mg/L
 Post-Actiflo and post-MIOX TTHM levels
0.023 mg/L
 TTHM levels reduced by 63% in total
Total HAA5 Reduction
 Pre-Actiflo and pre-MIOX HAA5 levels
0.040 mg/L
 Post-Actiflo and post-MIOX HAA5 levels
0.016 mg/L
 HAA5 levels reduced by 60% in total
THANK YOU!!
ANY QUESTIONS?