Membrane Bioreactor vs. Extended Aeration Treatment Pilot Study – Effluent and Groundwater Quality Presenter Leslie Dumas September 15, 2009 Innovative Solutions for Water and the Environment
Acknowledgements Thanks to: Colin Moy, REA., East Bay Municipal Utility District [EBMUD] – Project Manager Eileen Fanelli, P.G., East Bay Municipal Utility District/Presidio Trust – Project Manager David W. Smith, Ph.D., Merritt Smith Consulting – Principal Investigator
Background • WateReuse Foundation Project WRF-04-016 • Project Title: Development of Regulatory Protocol for Incidental Environmental Reuse of Title 22 Recycled Water Issued August 2005 to EBMUD with RMC Water & Environment EBMUD’s ‘upcountry’ wastewater systems needs: • Upgrading systems to meet evolving regulatory requirements • Beneficial reuse of treated effluent • Use of small MBR treatment systems
The Pardee Site
Key Challenges to Recycling in California • Regulatory Compliance - Resolution #68-16 Antidegradation Policy • Cost-Benefit for Small Systems Higher capital cost to implement MBR treatment Little to no reduction in longer-term operating costs Permitting costs increase overall capital costs
Study Goals • Recognize baseline assumptions on meeting CCR Title 22 standards for unrestricted use • Provide a standardized process (Framework) for evaluating recycled water projects • Utilize established and industry-accepted tools and practices for assessment
A Two-Part Study Approach was Used • Develop a Framework (standardized process) • Conduct a Pilot Test
Pilot Study Design • Conducted over 12 month period • Sampled and analyze influent, effluent and groundwater quality from both existing and pilot systems • Apply data to Framework analysis • Identify key operating differences between the extended aeration and MBR treatment plants
Treatment Trains PACT Extended Aeration Plant Schematic Pilot MBR Plant Schematic
Conventional Plant
Pilot Plant
Pilot Plant
Pilot Plant
Pilot Plant
Pilot Plant
Pilot Program Analytical Plan Parameter Influent Effluent Groundwater Settleable Solids (SS) Total Suspended Solids (TSS) pH Dissolved Oxygen Total Dissolved Solids (TDS) Turbidity Biological Oxygen Demand (BOD 5 ) Chemical Oxygen Demand (COD) Total Organic Carbon (TOC) Total Kjeldahl Nitrogen (TKN) Ammonia (NH 3 - N) Nitrate (NO 3 – N) Total Coliform Bacteria (after disinfection) Viruses (after disinfection) General Minerals Metals Trihalomethanes (THMs) Halogenic Acetic Acids (HAAs) n-Nitrosodimethylamine (NDMA)
Influent W ater Quality Analysis • Influent quality was consistent throughout the pilot study • Influent from PACT is found to be consistent with a low-strength municipal wastewater • Constituent concentrations appear to be on the same order of magnitude for both pre- and pilot- period influent data based on a trend analysis.
Effluent W ater Quality Analysis 1. Confirm the assumption that the MBR effluent met disinfected tertiary-treatment criteria 2. Identify the main differences in effluent quality produced by the extended aeration and the MBR pilot systems 3. Compare to groundwater quality over the pilot study period
Comparison of Expected and Actual MBR Effluent Quality Parameter Units Published Pilot MBR Effluent Quality Expected Effluent Value Average Range BOD 5 mg/L < 5 1.2 ND (< 2) - 2.2 TSS mg/L < 1 Not Sampled Not Sampled Ammonia mg/L as N < 1 0.63 ND (<0.3) - 6.72 Nitrate mg/L as N NA 30.03 0.19 – 53 Total Kjeldahl Nitrogen (TKN) mg/L as N NA 1.58 ND (< 1) – 11 Nitrite mg/L as N NA 0.16 ND (<0.0035) – 0.44 Total Nitrogen mg/L as N < 3 32.40* 0.19 – 71.16* Total Phosphorous (measured mg/L < 0.2 6.8 1.7 - 9.9 as Orthophosphate as P) Turbidity NTU < 0.2 0.34 0.13 – 1 Bacteria (measures as Total Log removal Up to 6 log 23.3 ND (< 2) – 230 Coliform) (99.9999%) Viruses Log removal Up to 3 log ND ND (99.9%)
MBR Effluent W ater Quality Analysis - Results • Improved for clarity, aluminum removal and BOD degradation • No difference for nitrogen, phosphates, total dissolved solids and most metals • Reduction in lead, manganese, and orthophosphate • Poor denitrification (no change in TKN, ammonia and nitrate concentrations)
Groundwater W ater Quality Analysis • Water quality analyzed to: characterize groundwater quality for both the pre- and MBR pilot periods Identify statistical differences that could be attributable to the MBR pilot system • The aquifer underlying the effluent pond is composed fractured bedrock • Used major ionic species to ‘fingerprint’ the water quality
Piper Diagram shows no difference between pilot and pre-pilot groundwater quality
Similar shaped Stiff Diagrams support the same conclusion Pre-Pilot Data Pilot Data
Groundwater Quality Results did not Reflect Change in Effluent Quality • Few anomalies observed, but longer monitoring required to determine cause • Pre- and pilot effluent qualities are significantly different from groundwater • No changes in groundwater quality may be result of: slight change in effluent chemistry low volumes of effluent discharged to pond short monitoring period
Study Conclusions • MBR system produced generally better effluent • MBR system was efficient in biodegradable and organic compounds removal • MBR was not efficient in phosphorus removal or denitrification • Groundwater does not appear to be impacted by either pre-pilot or pilot data over the monitoring period Based on testing, not reasonable to upgrade plant to achieve improved environmental results
The Framework was Tested with Pilot Data • Highlighted need for thorough data collection • Demonstrated flexibility needed in developing the reuse scenario
The Full Report • A Protocol for Estimating Potential Water Quality Impacts of Recycled Water Projects: Final Report and Pilot Test Results ; WateReuse Foundation: Alexandria, VA. 2009. • A Protocol for Estimating Potential Water Quality Impacts of Recycled Water Projects: Framework and User Guidance ; WateReuse Foundation: Alexandria ,VA. 2009.
QUESTIONS?
Framework Design • Internally consistent process • Early disclosure of potential impact • Allow project refinement to address possible impacts • Rely on established analytical tools and accepted industry practices • Apply on a constituent basis • Broadly applicable • Scalable relative to both project size and number of constituents of potential concern
Framework Analysis Process Figure 1 – Framework Analysis Process Figure 1 – Framework Analysis Process Consists of two main elements Preliminary Screening Detailed Site Evaluation
Preliminary Screening Process Step 1 –Water Quantity Analysis Step 2 –General Water Quality Analysis Step 3 – Screen Applicable Guidelines and Regulations Assumptions Meets criteria for disinfected tertiary recycled water Beneficial reuse for irrigation at agronomic rates Storage not in a water of the United States Outcomes Identification of constituents of potential concern Identification of applicable water quality goals and objectives Identification of site-specific parameters for detailed analysis
Detailed Site Analysis Process Step 4 –Prepare site assessment focused on vegetation, soil geochemistry and soil hydraulics Step 5 –Complete the constituent analysis Assumptions Rely on site-specific data or literature values ,as appropriate Outcomes Refine list of potential constituents of concern Estimate short and long term magnitude of potential impact Identify options for mitigating potential impacts
Framework Tools Nutrients (nitrogen and phosphate) Nutrient budget Salts (measured by water and soil salinity & sodicity) Determination of leaching fraction relative to assimilative capacity Metals (aluminum, copper, lead, nickel & zinc) Metals inventory and attenuation Organic carbon (as precursor for disinfection by- products and HAA formation) Effluent organic matter (EfOM)
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