Where Princeton's Wastewater Goes

When Hurricane Sandy hit, Princeton's wastewater treatment plant lost power like everyone else. That's a big deal, because sewage doesn't miraculously stop flowing, and a powerless treatment plant means 13 million gallons of raw sewage a day pouring straight into the Millstone River.

Fortunately, the Stony Brook Regional Sewerage Authority, as it's properly called, was able to get 9000 gallons of fuel oil per day trucked in to run backup generators--not easy when trees were blocking roads and fuel oil was scarce. Also fortuitous, the hurricane brought the Princeton area relatively little rainfall with the high winds. Heavy rains would have seeped via groundwater into aging sewers, adding substantially to the quantities of wastewater the plant had to process while it was running on backup power.

What was most striking for me, in talking to the plant manager after the hurricane, and previously to the executive director, is the millions of dollars of energy required to deal with the wastewater that drains silently from our homes, businesses and institutions into the great underground labyrinth of pipes leading eventually to the River Road plant. My scribbled notes are not the last word on the subject, but here's what I have:

• In addition to Princeton, the plant treats sewage from West Windsor, Plainsboro, Pennington and part of South Brunswick. Princeton's share of total flow is 40%. 
• Though 13 million gallons a day is typical, the amount of wastewater coming into the plant can vary considerably. Heavy rains can send addition water pouring down manholes or seeping from groundwater into leaky pipes. 
• Some Princetonians have their sump pumps discharging not into the backyard or the street, but into the town's sanitary sewer (the one that takes wastewater to the plant for treatment, as opposed to the stormwater sewer, which pipes rainwater runoff directly into Lake Carnegie). This adds an unnecessary burden to the sewer system and expense that all of us have to bear.
• Of a total annual budget of $15 million, $2 million goes to electricity, and another million or so is spent on natural gas to incinerate the sludge. (Before natural gas dropped in price, the cost was more like $2.3 million/year.) Princeton's share, according to my notes, is $800,000 for electricity and $600,000 for the natural gas. Though they can point to "variable frequency drive" pumps and other efforts to improve efficiency, that's a lot of greenhouse gases Princeton is sending up into the atmosphere.
• I was surprised to learn that Princeton's sewage sludge, which one would think is relatively uncontaminated, is not being utilized for fertilizer. Philadelphia turns a portion of its sludge into a dried product that can be sold. Ocean County, NJ, sells its sludge as pellets. But back in 1978, state and federal funds were available to fund 90% of the cost of building an incinerator in Princeton, and the offer was too good to refuse. Though that might not be the approach they'd go with today, the Stony Brook plant is sticking with its incinerator for now. The ash ends up in the Warren County landfill.
• According to the plant manager, only 27% of New Jersey's sludge is incinerated. Some sludge is sent to Texas or Ohio for use on fields. 
• There's some discussion of installing a large solar panel array on land behind the plant, which would supply 10% of the plants electricity. 

Bottom lines (since these are the bottom lines of the post):

1. Wasted water down the drain = additional greenhouse gases up in the atmosphere. Along with finding ways to use less water day to day in the house, check the sump pump if you have one, and make sure it pumps the water outside rather than into the sanitary sewer.
2. Princeton's sludge, which surely is some of the finest to be had, with substantial contributions from Nobel Laureates and other cultural elites, is not put to use growing prize-winning foliage but instead sent into firey oblivion and buried underground, never to return to the cycle of life.
3. A New York Times article last year described New York City's effort to utilize its sludge for energy production and possibly also fertilizer. Here's a quote: "The biggest potential source of energy, officials said, is the methane gas from sewage treatment plants’ digesters. About half of the methane produced by the city’s plants is already used to meet about 20 percent of the energy demands of the city’s 14 sewage plants, whose electric bills run to a total of about $50 million a year. Now the city wants to market the other half, which is burned off and wasted."