Innovative Solutions for Water and the Environment

Membrane Bioreactor vs. Extended Aeration Treatment Pilot Study – Effluent and Groundwater Quality

PresenterLeslie Dumas

September 15, 2009

Acknowledgements

Thanks to:Colin Moy, REA., East Bay Municipal Utility District

[EBMUD] – Project ManagerEileen Fanelli, P.G., East Bay Municipal Utility

District/Presidio Trust – Project ManagerDavid 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

Pilot MBR Plant Schematic

PACT Extended Aeration Plant Schematic

Conventional Plant

Pilot Plant

Pilot Plant

Pilot Plant

Pilot Plant

Pilot Plant

Pilot Program Analytical PlanParameter Influent Effluent GroundwaterSettleable Solids (SS) Total Suspended Solids (TSS) pH Dissolved Oxygen Total Dissolved Solids (TDS) Turbidity Biological Oxygen Demand (BOD5) Chemical Oxygen Demand (COD) Total Organic Carbon (TOC) Total Kjeldahl Nitrogen (TKN) Ammonia (NH3 - N) Nitrate (NO3 – N) Total Coliform Bacteria (after disinfection) Viruses (after disinfection) General Minerals Metals Trihalomethanes (THMs) Halogenic Acetic Acids (HAAs) n-Nitrosodimethylamine (NDMA)

Influent Water 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 Water 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 Expected Effluent Value

Pilot MBR Effluent Quality

Average RangeBOD5 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 as Orthophosphate as P)

mg/L < 0.2 6.8 1.7 - 9.9

Turbidity NTU < 0.2 0.34 0.13 – 1

Bacteria (measures as Total Coliform)

Log removal Up to 6 log (99.9999%)

23.3 ND (< 2) – 230

Viruses Log removal Up to 3 log (99.9%)

ND ND

MBR Effluent Water 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 Water 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

Consists of two main elements Preliminary Screening Detailed Site Evaluation

Figure 1 – Framework Analysis ProcessFigure 1 – Framework Analysis Process

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)