by Joe Eyre
On 3/1/12 I attended the last public informational meeting held by the staff of the Palo Alto Regional Water Quality Control Plant. This is the facility that treats the sewerage from Los Altos and Los Altos Hills as well as Palo Alto, Stanford, and Mountain View. The staff has been doing long range planning and this particular meeting focused on liquids treatment and then looked at the overall plant recommendations. The plant was built in 1972 and requires continual upgrading due to wear and/or new regulations.
Liquids treatment has several steps ranging from settling to disinfecting. During this process the plant removes CBOD’s solids, and total ammonia as nitrogen. Looking ahead, the staff is concerned about regulations limiting the amount of nitrogen and emerging constituents that can be discharged with the processed water. Today, neither of these are removed and flow directly out with the discharged water into the bay and harming fish and wildlife. Nitrogen causes algae bloom which depletes oxygen from the water and killing aquatic life. The emerging constituents are pharmaceuticals, endocrine disruptors (such as birth control pills and estrogen) and the chemicals from anti-bacterial soap. As an individual, you can help by limiting the dumping of these chemicals into wastewater.
The staff showed three different approaches to liquids treatments, looking at their costs and the amount of greenhouse gases they emit. Not surprisingly, the cheapest option emits the most greenhouse gases.
One big issue the plant has is that water seeps into the sewer system and increases flows dramatically from something like 22 million gallons/day to up to 80 million gallons a day. This extra water comes from stormwater during winter rains and seepage from bay water which gets into the sewer pipes flowing from Mountain View and through the bay. This requires the plant to size up their equipment to handle a lot more capacity than the sewer-only flows require.
The plant recycles some water (about 5-8%) and this is used for landscape water at the Palo Alto and Shoreline golf courses. However, this water has about 1.5 times the salinity that plants can comfortably handle and so the facility needs to reduce the salinity of the recycled water. Some of salinity comes from old water softeners but most of it is coming from the Mountain View pipe flowing through the bay which allows bay water into the line. Mountain View is working to line these pipes so they let less bay water into them.
Looking forward they need to figure out the best way to get rid of biosolids, the stuff that settles or is extracted from the water. Options include different treatments on site or trucking it to San Jose which has excess capacity.
As an interesting aside, a representative from Stanford was in the audience. Stanford contributes about 4% of the daily flows to the facility but the biggest water user on the Stanford campus is the cooling tower of their power plant (this is pretty typical around the US — so the more electric you use, the more water you use). An exciting initiative there is that all new building is designed not to increase the stormwater runoff. They are using different building and retention techniques to keep stormwater on site. This is good because stormwater carries chemicals into creeks, causes erosion and flooding, and as mentioned above, some of it flows into the sewer system.
This was the last informational meeting and the next step is for the staff to put together detailed financials and present their recommendations to the Palo Alto City Council.
For a copy of the presentation, click on “Carollo Engineers March 2012 Presentation” on the following site: http://www.cityofpaloalto.org/depts/pwd/news/details.asp?NewsID=1471&TargetID=65#Planning Process Documents