Protecting Municipal Water by Passively Treating Agricultural Runoff

Report
RETHINKING WATER:
PROTECTING MUNICIPAL WATER
BY PASSIVELY TREATING
AGRICULTURAL RUNOFF
CALIFORNIA ASSOCIATION OF RESOURCE CONSERVATION DISTRICTS
SHANNON SWEENEY, WATER RESOURCES MANAGER, CITY OF SANTA MARIA
ANNE COATES, CACHUMA RESOURCE CONSERVATION DISTRICT
THURSDAY,NOVEMBER 13, 2014
SANTA MARIA VALLEY
GROUNDWATER BASIN
• BENEFICIAL USES INCLUDE:
• AGRICULTURAL SUPPLY
• MUNICIPAL SUPPLY
• GROUNDWATER BASIN CONNECTED TO SURFACE
WATERS WITH BIOLOGICAL, RECREATIONAL USES.
• IMPACTED BY NITRATE, WHICH AFFECTS ALL OF THE
BENEFICIAL USES.
CITY OF SANTA MARIA MUNICIPAL
SUPPLY
• CITY OF SANTA MARIA HAS TWO SOURCES OF DOMESTIC
WATER SUPPLY:
• STATE WATER: HIGH QUALITY, VARIABLE SUPPLY
• GROUNDWATER: VERY RELIABLE, VARIABLE QUALITY
• DOMESTIC SUPPLY NEEDS TO MEET STATE AND FEDERAL
WATER QUALITY STANDARDS FOR NITRATE AND TOTAL
DISSOLVED SOLIDS.
GROUNDWATER SUPPLY AND QUALITY
• CITY PRODUCTION
WELLS HAVE VARIABLE
QUALITY.
• TESTING SHOWS LOWER
WELL PERFORATIONS
LOWER IN NO3 THAN
UPPER PERFORATIONS.
WELL 9 DYNAMIC FLOW PROFILING
RWQCB AGRICULTURAL ORDER
• FARMERS SEEK LOW NITRATE IRRIGATION WATER TO LOWER
NITRATE IN RUNOFF, OR AVOID RUNOFF COMPLETELY.
• PROBLEMS – IF EVERYONE DIGS DEEPER WELLS, THEN
“LOWER” AQUIFER BECOMES IMPACTED ALSO. LEAVING
WATER ONSITE LEADS TO SALT BUILDUP – BAD FOR FARMERS
AND MUNICIPAL SUPPLY.
• REGIONAL BOARD’S NUTRIENT CONCERNS: DOWNSTREAM
BIOSTIMULATORY EFFECTS (ALGAL BLOOMS) AND RECHARGE
FOR MUNICIPAL SUPPLY
UC DAVIS REPORT FOR THE SWRCB
SBX2 1 REPORT TO THE LEGISLATURE
• 2008 – SBX2 1 SIGNED INTO LAW – REQUIRES A
STUDY TO BETTER UNDERSTAND NITRATE ISSUES.
• FINISHED PRODUCT: ADDRESSING NITRATE IN
CALIFORNIA’S DRINKING WATER.
• KEY FINDING: “DIRECT REMEDIATION TO REMOVE
NITRATE FROM LARGE GROUNDWATER BASINS IS
EXTREMELY COSTLY AND NOT TECHNICALLY
FEASIBLE. INSTEAD, “PUMP-AND-FERTILIZE” AND
IMPROVED GROUNDWATER RECHARGE
MANAGEMENT ARE LESS COSTLY LONG-TERM
ALTERNATIVES.”
Main Issue: How can farmers “pump and
fertilize” without letting nitrate-impacted
runoff affect downstream uses, while
still removing salts?
One thought: If nitrate is removed from
the runoff, then salts can move to a
proper sink (the ocean!) and municipal
supply can be protected from both salts
and nitrate.
DRAINAGE
• MOST OF SM VALLEY
DRAINS THROUGH
DISCRETE POINTS TO SM
RIVER.
• THESE DISCRETE PATHS
LEND THEMSELVES TO
TREATMENT LOCATIONS.
NUTRIENT REMOVAL
• BIOLOGICAL TREATMENT FOR NUTRIENT REMOVAL IS
COMMON:
• WETLANDS – NEED LARGE FOOTPRINT
• TERTIARY WWTP’S – LABOR INTENSIVE, LARGE CAPITAL
INVESTMENT
• BIOFILTERS – PASSIVE TREATMENT, LOW FOOTPRINT
• SOLUTION NEEDS TO MAXIMIZE NITRATE REMOVAL
WITH SMALL FOOTPRINT AND LITTLE INVOLVEMENT.
BIOFILTER CONCEPTS
• FACULTATIVE ANAEROBES CONVERT AMMONIA TO NITRATE
WHEN OXYGEN IS PRESENT.
• SAME BACTERIA SCAVENGE OXYGEN OFF NITRATE IN THE
ABSENCE OF OXYGEN. NITRATE IS CONVERTED TO NITROGEN
GAS.
• PROCESS NEEDS A SUBSTRATE, A CARBON SOURCE, AND
SUFFICIENT TIME FOR BACTERIA TO GROW AND METABOLIZE.
• CONSTANT FLOW AND NUTRIENTS HELP, TOO.
WOODCHIP BIOFILTER
• WOODCHIPS PROVIDE THE
CARBON AND THE SUBSTRATE
• CITY & COUNTY SUPPORT
INSTALLATION AT JIM MAY
PARK, FOR TREATING WATER
FROM BRADLEY CHANNEL.
• BRADLEY CHANNEL DRAINS
5,700 ACRES OF AG LAND,
913 ACRES OF URBAN LAND.
• FEASIBILITY STUDY
COMPLETED. EXPECTED TO
REMOVE UP TO 50,000 LBS
NITRATE PER YEAR.
El Centro, CA
CAN THIS HAPPEN?
• FILTER IS A PHYSICAL
SOLUTION IN NEED OF
FUNDING.
• RCD GRANT HAS FUNDING
NOT OTHERWISE AVAILABLE TO
A MUNICIPAL AGENCY.
• RWQCB SUPPORTS THIS
EFFORT.
JIM MAY PARK BIOFILTER
• TREATS AGRICULTURAL RUNOFF FROM 5700 ACRES
• 20 GAL/MIN WITH NITRATE EXCEEDING 80 MG/L
• EXPECTED REMOVAL OF UP TO 50,000 LB/YR NITRATE

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