A new consulting report states that Wareham's sewer plant has the capacity to serve all the  neighborhoods committed to be sewered, the A.D. Makepeace development, and Union Pond housing development - plus an additional 225,000 gallons of wastewater.

However, to accommodate the additional 225,000 gallons, the plant will have to be "rated" again and obtain new permits.

Presented at a Thursday, July 1, workshop meeting of Selectmen, who also serve as Sewer Commissioners, the report from Camp, Dresser and McKee was seen as containing good news: The town does not have to immediately build a new, multi-million-dollar sewer plant to handle already-committed sewer projects.  And the permitting process to accommodate sewage from some additional system expansion would cost significantly less than building a new plant.

The report was also seen as containing bad news:  Selectmen and members of the audience were not convinced that new permitting would be possible, based on the Environmental Protection Agency's limit on the discharge from the plant.

"225,000 gallons could theoretically be added by doing minor adjustments without having to do a full upgrade," explained Selectman Brenda Eckstrom. "But the EPA will not allow us to discharge any more than what we are discharging currently."

Furthermore, Eckstrom expressed concern about the data used in the presentation.  For instance, the numbers that the study used as the wastewater produced by the A.D. Makepeace development were half those requested by the company when it appeared before the Board of Selectmen.

"Makepeace would not ask for something that they did not need," said Eckstrom. "To say we have the capacity based on these (reduced) numbers, that could be very problematic."

Consultant Al Firman of CDM expressed confidence in the numbers.  But he emphasized that, it was a "preliminary summary."  Furthermore, although based on industry standards of average daily use, he said the numbers might not most accurately reflect the needs of a community such as Wareham which has significant seasonal fluctuations in its wastewater.

"The average probably never happens, except at the end of the year when the total numbers are divided by 365," said Firman, explaining that Wareham has to be much more concerned with whether the plant can handle peak flow amounts as opposed to typical daily amounts. In other words, it is more important that the plant can handle the wastewater after a rainy 4th-of-July weekend than the amount of wastewater sent to the plant on the typical day in February.

Nevertheless, the presentation provided an overview of the challenges that Wareham faces in its wastewater treatment.

Wareham has two major and closely related issues in treating wastewater: the capacity of the sewer system to handle the "flow" of wastewater, and the system's ability to handle the "load" of organic compounds - specifically nitrogen - that it needs to eliminate from the wastewater.

In terms of flow capacity, the sewer plant can handle an average inflow of 1.56 million gallons of wastewater per day (mgd). In 2009, Firman reported that the average inflow was 1.07 mgd. Future commitments will contribute .43 mgd, for a total sum of 1.5 mgd.

However, the more important number for Wareham is the peak hourly and daily inflow. This is 2.0 mgd.

To accommodate a seasonal population that contributes wastewater only for approximately three months a year, (and since many of the predominantly summer communities are currently, or are scheduled to be, serviced by the sewer) the peak flow capacity per was sized 10% higher than similar-sized plants when the $24 million plant was completed in October 2005.

When the flow exceeds 2.0 mgd, the plant stores the additional flow in tanks where it is aerated and mixed, allowing bacteria to thrive and solids to settle to the bottom of the tank.  (If you've ever walked by a treatment plant, these are the open pools that look like they have a fountain in them and smell a little bit funky).  When the flow rate at the plant has subsided, the excess flow is then pumped through for further treatment. Firman also noted that it is also significantly cheaper to add storage capability to handle peak flow than to replace the infrastructure to handle daily flow.

But while the flow is pretty straightforward - you essentially either have pipes big enough to handle it or you don't - dealing with the nitrogen load is more complicated.

The acronym for this issue is "BOD" or biochemical oxygen demand. Basically, bacteria and chemicals are used to remove nitrogen and other organic byproducts, and these require oxygen to live. The plant was designed to handle a daily average of 3,752 pounds of wastewater as well as 997 pounds of septage per day. (Septage is the waste pumped from private septic systems and then trucked to the plant to be treated.  The town charges septic haulers a fee to dispose of this waste.)

The numbers indicate that with the planned development, we will hit that septage capacity. However, this is where the many variables in dealing with sewers and nitrogen load, for lack of a better phrase, "muddy the water."

As more neighborhoods are tied into the sewer, the amount of septage being treated  will decrease as it is replaced by sewered wastewater.

Furthermore, the fluctuations in seasonal wastewater are hard to manage in terms of nitrogen treatment. Wareham needs more bacteria (and oxygen) in the summer than winter, when more wastewater with more organic compounds is being produced.

As a result, the nitrogen levels in the treated water that the town discharges from the plant is very different.  During the summer months when flow is highest, nitrogen levels register at 2 million gallons per liter (mg/L).  In the winter months, these levels jumps to 11 mg/L.

While this fluctuation is permissible, as the State measures the annual average (there we go with averages again), it isn't ideal.

"The magic number is 3," Firman explained.  "You want to keep these levels about the same."

But that is hard to do. You can't really just dump bacteria into the water every spring and then remove them in the fall. Like any aquarium owner knows, you have to condition your tank slowly to maintain the ideal chemical and biological conditions for fish - Same with a wastewater treatment plant and bacteria. With the town's seasonal fluctuations in flow, it becomes even more difficult.

Then there is the impact of new technology. Eckstrom pointed out that the numbers used in the report for the Union Pond project were too high: To place less of a burden on the sewer, the developer installed "low flow" devices. While this helps decrease the flow, it puts a burden on the "load" because the organic matter that needs to be removed is more concentrated - meaning we need more bacteria and chemicals to treat the water.  Thus the "formula" for treating wastewater is constantly in flux.

Among the unanswered questions: Will 225,000 gallons of capacity, (roughly equivalent to 681 three-bedroom houses based on the industry standard that each bedroom uses 110 gallons per day) make it necessary to expand the sewer system in two years, ten years, twenty years? Can the formula to treat nitrogen be changed to handle the fluctuations in flow?  Can Wareham even get the permits for additional discharge?

It's difficult to determine. But it is something that will be affecting Wareham for years to come.

And of course, this doesn't even touch on the most contentious issues:  How much will any of these necessary changes cost? And how will they be paid for?