By Chad C. Bertram
Through continuously sampling, analyzing, and monitoring water quality, as well as working with property owners and other agencies to encourage proper use of watershed lands, the ACWD’s efforts ensure water quality is protected and maintained. The use of handheld metering systems plays a vital role in the district meeting this objective.
The Alameda County Water District (ACWD) serves a 103 square mile area that includes the cities of Fremont, Newark, and Union City, California. ACWD serves a population of approximately 325,000 customers and has an average water production of 45.89 million gallons per day.
ACWD’s four sources of water supply include approximately 55 percent from the State Water Project, which is either purified at one of the district’s treatment facilities or used to recharge local aquifers. Water from Hetch Hetchy Reservoir provides approximately 30 percent of the district’s water, and runoff from the Alameda Creek Watershed accounts for the remaining 15 percent.
Watershed Monitoring
Field analysis is essential for protecting the integrity of the watershed, where runoff is used to recharge the aquifers of the Niles Cone Groundwater Basin. Sixteen wells in the basin extract water that is then blended with Hetch Hetchy water before being delivered to customers. The district continuously samples, analyzes and monitors the quality of water in Alameda Creek at key locations throughout the watershed as well as several hundred acres of percolation ponds that also recharge the underlying groundwater basin.
At these monitoring points, dissolved oxygen (DO), pH, and conductivity are three key field-testing parameters.
“We monitor at more than a dozen different sample points along Alameda Creek as well at our percolation ponds,” said John Marchand, Senior Chemist at the Water District Water Quality Laboratory. “Dissolved oxygen measurements provide us with a good indication of the health of the reservoir and the health of our streams. By measuring DO, for example, we can determine that a body of water has not gone septic and that there’s good circulation through the water column.”
The effect of oxidation on streams and the progress of self-purification can both be measured or estimated from the dissolved oxygen content.
In addition to measuring DO on a scheduled basis, field conductivity and pH measurements are also important for the district in monitoring the health of the watershed.
“With these two parameters we can detect if there have been any spills or potential contamination. Also, with conductivity measurement, we can actually determine which tributaries are coming in - in other words we can determine how much flow is coming in from a certain area that could impact the watershed. And, depending upon the stream we are monitoring and where the water is coming from, we can actually identify where we have certain impacts within the watershed. For example, there are two gravel quarries in the district that discharge groundwater into streams, and through conductivity field measurements we can determine when one of these quarries is impacting our streams.”
Assessing New Instrumentation
The Alameda district recently participated in beta testing a new portable electrochemical meter that is the first instrument for field and laboratory use that does not require the user to predetermine parameters. Because of the intense scheduled monitoring of the watershed, handheld instruments play a critical role in day-to-day operations - to quickly gather “snapshots” of conditions of the district’s numerous water sources. Until recently, field personnel had used four separate handheld instruments to measure DO, pH, conductivity, and temperature.
The district beta tested the Hach HQ40d® electrochemical meter with IntelliCALTM probes. With this new unit a user can take up to two simultaneous measurements (and readouts) of pH, conductivity, LDO® (Hach’s Luminescent Dissolved OxygenTM technology), and ORP. The HQd-series of meters has an intuitive user interface with guided self-calibration. The last calibration as well as calibration history is stored in the plug-and-play probe, reducing the need to recalibrate when switching between parameters. The system provides reporting data, including time and date, sample ID, and user ID, so that users can store and monitor previous readings.
“We’ve found it’s convenient having a single portable instrument that measures all the parameters we measure in the field (DO, conductivity, pH, and temperature) rather than have four different meters, one for each parameter,” Marchand said.
For DO measurement, the Hach beta unit provided a number of advantages over the district’s portable membrane-type DO meters, he said.
“For one thing, the new unit’s probes are self-calibrating. Our membrane-type DO units need frequent calibration and you can only do that in the lab by running it against the Winkler Method, which is time-consuming. Also, the LDO probes don’t require reagent. Our fluid-filled membrane DO meters can be very temperamental, and when you replace the membrane you have to stretch this little saranwrap-like membrane across the top, which can be a hassle, especially when you’re in a hurry.”
Marchand said that, throughout the month-long beta test period, the new Hach meter locked in quickly and repeatability was excellent with all parameters tested.
“We also use handhelds at our treatment plants to check individual filters, for example, and our settling basins. These plants are equipped with both online and instantaneous monitoring, and we found a tight correlation of the Hach beta unit to those online systems. The response time for all parameters was comparable if not quicker than most of our other units.”
Datalogging & Durability
The district found that swapping out probes/parameters with the beta unit was relatively simple and did not require recalibration.
“The probes remember their last calibration and alert the user to when re-calibration is needed,” Marchand said. “We can just unplug the pH probe and then plug in conductivity without having to recalibrate it. The meter recognizes the new probe that’s been plugged in and responds to the last calibration.”
The meter’s 500-point event log stores measurements, calibrations and check standards.
“We can store our readings in the meter while in the field and download them into our computer once we get back to the laboratory,” Marchand said.
Readings can also be downloaded to a portable flash stick.
Conclusion
Field analysis plays an important role at Alameda County Water District (ACWD), especially in monitoring the watershed that recharges key aquifers serving the district. Through continuously sampling, analyzing, and monitoring water quality, as well as working with property owners and other agencies to encourage proper use of watershed lands, the ACWD’s efforts ensure water quality is protected and maintained.
The use of handheld metering systems plays a vital role in the district meeting this objective. Not only must portable instrumentation provide accurate, repeatable measurement, it must also be easy to use and calibrate and be sufficiently durable to hold up to constant field use. Based on recent beta testing, the new metering units and probes have demonstrated these capabilities to the district while also providing preprogrammed methods for multiple analyses and comprehensive data storage features.
About the Author:
Chad C. Bertram is Program Manager & Product-Line Manager for Hach Company Phone: 970-663-1377 x2644 [email protected].
