SOUTH GRANVILLE WATER & SEWER AUTHORITY Disinfection By-Products Reduction and SCADA Evaluation and WTP Sludge Removal System and Dewatering Facility Presentation to the SGWASA Board October 10, 2017
TTHM (mg/l) Locational Running Annual Average (LRAA) for TTHM 0.10 0.09 B01 B02 B03 B04 0.08 MCL for TTHM 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 3/2/2014 12/27/2014 10/23/2015 8/18/2016 6/14/2017 4/10/2018
HAA5 (mg/l) Locational Running Annual Average (LRAA) for HAA5 0.09 B01 B02 B03 B04 0.08 0.07 0.06 MCL for HAA5 0.05 0.04 0.03 0.02 0.01 0.00 3/2/2014 9/18/2014 4/6/2015 10/23/2015 5/10/2016 11/26/2016 6/14/2017 12/31/2017
Project Approach Bench-Scale Testing Develop bench-scale testing protocol that simulates WTP performance plant match Evaluate alternate coagulant types, doses, and ph Evaluate need for, type, and required dosage of coagulant aid polymers, pre-oxidants, and PAC Goal is to assess optimal strategies for DBP precursor removal Holistic approach need to ensure that any strategy does not compromise other treatment goals
Jar Testing Calibration Parameter Full-Scale Jar 1-4 KMnO 4 (mg/l) 2.5+0.4 2.5+0.4 PAC (mg/l) 8 8 Ferric Sulfate (mg/l) 65 80 ph (Units) 4.76 4.88 UV-254 (1/cm) 0.022 0.024 Turbidity (NTU) 0.64 0.56 Alkalinity (mg/l) 2 2 Temperature ( C) 23 23
UV Absorbance (1/cm) Both ferric sulfate and ferric chloride can provide good UV reductions No Polymer, ph Adjusted to 5.5-5.7 Ferric Sulfate Ferric Chloride 0.12 0.1 0.096 0.08 0.06 0.068 0.074 0.04 0.02 0.038 0.041 0.037 0.033 0.033 0.033 0.033 0.033 0.029 0 30 40 50 60 70 80 90 100 Coagulant Dose (mg/l)
Settled Water Turbidity (NTU) and UV Absorbance (1/cm) Ashland 851 TR can provide better results than the currently used Clarifloc N6310 9.0 UV Absorbance Settled Water Turbidity 8.0 7.0 6.0 5.0 7.22 7.70 4.0 3.0 2.0 1.0 0.0 2.92 1.50 1.01 0.92 0.033 0.039 0.041 0.043 0.042 0.036 851 TR LT22s N300 LT20 650 TR N6310
TOC (mg/l), TTHM (µg/l), THAA (µg/l) Simulated Distribution Samples - DBPs Lake TOC: 10.2 mg/l, Reservoir TOC: 9.2 mg/l 80 TOC TTHM THAA FeCl=Ferric chloride FeS=Ferric sulfate 70 67.4 60 50 51 40 30 20 10 0 16 17 18 12.4 11.6 11.6 3.9 3.3 4.1 3.2 60 FeCl No Oxidant 60 FeCl 0.5 ClO2 60 FeS w/851tr Full Scale Tap
TTHM (mg/l) TOC (mg/l) Good TTHM correlation with TOC 0.14 0.12 0.10 B01 B02 B03 B04 Reservoir TOC CFE TOC Alum Ferric Sulfate 18.0 16.0 14.0 12.0 0.08 10.0 0.06 8.0 0.04 0.02 6.0 4.0 2.0 0.00 1/31/2016 6/29/2016 11/26/2016 4/25/2017 9/22/2017 0.0
HAA5 (mg/l) TOC (mg/l) HAA5 vs TOC 0.12 B01 B02 B03 B04 Reservoir TOC CFE TOC 18.0 0.10 Alum Ferric Sulfate 16.0 14.0 0.08 12.0 0.06 10.0 8.0 0.04 6.0 0.02 4.0 2.0 0.00 1/31/2016 6/29/2016 11/26/2016 4/25/2017 9/22/2017 0.0
TOC Removal TOC removal over time 1 0.9 Alum Ferric Sulfate 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 3/21/2016 6/29/2016 10/7/2016 1/15/2017 4/25/2017 8/3/2017 11/11/2017
Process Schematic Chemical Addition DBP Sample Taken Flash Mix Effluent Influent Sed. Basin 1 Filter Effluent Pre and Post NH 3 Plant Tap
TTHM (mg/l) TTHM profile thru WTP FILTER EFF. PRE NH3 POST NH3 PLANT TAP 0.14 Alum Ferric Sulfate 0.12 0.10 0.08 0.06 0.04 0.02 0.00 6/29/2016 10/7/2016 1/15/2017 4/25/2017 8/3/2017 11/11/2017
HAA5 (mg/l) HAA5 profile thru WTP FILTER EFF. PRE NH3 POST NH3 PLANT TAP 0.10 0.09 Alum Ferric Sulfate 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 6/29/2016 10/7/2016 1/15/2017 4/25/2017 8/3/2017 11/11/2017
Project Approach Chemical Feed Evaluation In progress Site visit to assess existing facilities. Determine required storage and feed equipment capacities. Confirm compatibility of proposed changes. SCADA and Automation Evaluation Determine automation and SCADA system needs. Review SCADA system architecture at WWTP In progress Coordinate with any recommended process changes Example HMI Workstation
Preliminary Findings Conversion to ferric sulfate has enhanced TOC removal to 77% (66% prior to conversion) Conversion to ferric sulfate has reduced DBP formation (based on special samples) THMs are ~54% lower than 1 year ago (August 2016) HAAs are ~40% lower than 1 year ago (August 2016) Continue to investigate possible impacts of fullscale operations on DBP formation such as sludge collection system issues, process control, and chemical mixing
Schedule Aug 8 Aug 21 Oct 10 Nov 28 Notice to proceed Begin bench-scale testing Present bench-scale testing preliminary results Submit draft report Dec 12 Present draft DBP and SCADA evaluation recommendations
Questions and Discussion
WTP Sludge Removal System and Dewatering Facility
Project Approach A switch to an iron-based coagulant and additional PAC and potassium permanganate results in greater solids production. Residuals Collection System Assessment Evaluate existing equipment and coordinate with manufacturers Recommend improvements to enhance reliability Concept-level capital costs Residuals Production Estimates In progress In progress Critical to coordinate with DBP project
Project Approach 2-M Belt Filter Press Dewatering Alternatives New Dewatering Facility Thickening + Dewatering Relocate existing rotary drum thickener + dewatering Residuals lagoon Pending completion of prior tasks
Schedule Aug 8 Nov 1 Jan 15 Notice to proceed Preliminary DBP strategy informs possible range of residuals production Submit draft report
Questions and Discussion
UV Disinfection UV Disinfection is a physical process used for: Primary disinfection (i.e. CT requirements at the WTP) Advanced oxidation (UV AOP) UV does not produce a residual so a chemical disinfectant (free chlorine or chloramines) is also needed to provide a residual in the distribution system
UV Disinfection UV disinfection is effective for inactivation of bacteria, Giardia, and Crypto. UV disinfection is less effective for virus inactivation Log Inactivation 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Cryptosporidium 1.6 2.5 3.9 5.8 8.5 12 -- -- Giardia 1.5 2.1 3.0 5.2 7.7 11 -- -- Virus 39 58 79 100 121 143 163 186
Disinfection Mechanism Dimerization of DNA (thymine bases) Inability to Reproduce Bug is Non-infective UV does not kill pathogens Dimer Dimer 26
UV Disinfection Applications NC Public Water Supply has approved the use of UV disinfection for primary disinfection The City of Raleigh was first to obtain approval in 2013 UV can be part of a DBP control strategy Meet primary disinfection (CT) requirements at the WTP Reduces needed free chlorine contact time in WTP Monochloramine as secondary disinfectant However, free chlorine still has a place
UV Disinfection Applications Raw Water Feed free chlorine prior to filters for: Oxidation of iron and manganese Prevent filters from becoming biological Meet regulatory CT requirements for virus inactivation Ozone NaOCl NH 3 Ozone Contactor SuperPulsator GAC BioFilters Dual-Media Filters UV Disinfection To Distr. P Alt. NH 3 5-MG Storage Tank
If UV Disinfection Applied at SGWASA WTP Recommend continue feeding free chlorine in filter influent Move point of ammonia addition prior to chlorine contact tank to reduce free chlorine contact time Maintain ability for free chlorine disinfection as a backup UV Disinfection
If UV Disinfection Applied at SGWASA WTP Conceptual Capital Costs: $4.5-5.5 million An updated SCADA system would be required UV Facility would be a deep structure to keep UV reactors full of water Impacts on WTP electrical system and standby power?