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Wastewater systems and the environment

By Allison E. Weakley
Posted Saturday, February 7, 2004

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The most high tech versions of wastewater systems treat wastewater fairly well in terms of bacteria and other microbes that are a product of human waste. The problem with these systems is that water with nutrients are being sprayed onto soil/plants, and those nutrients (nitrogen, phosphorus, salts) often leach into groundwater or surface water by way of runoff. Phosphorus is especially problematic because it builds up in the soil over time which is a cumulative effect, and phosphorus is especially problematic in freshwater systems like Jordan Lake. Systems with spray fields often use golf courses/lawns/fields to absorb some of the nutrients. The problem is that, depending on the plants used (how well they absorb and process the nutrients), what is done with the plant material when mowed (is it left to decompose on site, therefore leaving nutrients to be released on site?), weather conditions (rainfall, humidity... things that affect evapotranspiration rates of the plants), soils on site, and a variety of other factors can affect how efficiently the system works.

For example, imagine a wet year (like last year), where the ground remains saturated pretty frequently. The operator that tends the spray fields has to spray effluent to avoid the wastewater in the holding ponds from spilling over the edge, so nutrient-rich wastewater is sprayed on top of already saturated ground. What's the likely result? Runoff. This is a perennial problem at the Governor's Club (the folks who play golf have been very upset that the course is so wet) and at The Preserve. And heaven forbid we have a hurricane or other storm with terrential rain! Plus, as you might guess, plants don't absorb nutrients when they are dormant, so what happens in winter when the water table is higher and groundwater is being recharged?

Leaking pipes are a constant maintenance problem.

Add to these scenarios the likelihood of problems with the system. Take The Preserve and Gov Club again, for example. The topography is steep (for the Piedmont), so lift stations must pump the water up and down hills to get the water where it needs to go. Leaking pipes are a constant maintenance problem, and both The Preserve and Governor's Club have had lots of these types of problems already.

Now compound these issues with the fact that many of these type developments approved for Chatham County lie in the already impared Jordan Lake watershed. Folks from federal, state, and local agencies (all stakeholders in the Jordan Lake watershed, except folks from Chatham County government!!!) have been holding meetings since last year trying to figure out how to manage nutrient loads in the lake. In fact, last year they were convinced that there would be a big fish kill!

What causes a fish kill? Eutrophic water -- too many dissolved nutrients currently exist in Jordan Lake, and these nutrients encourage the growth of blue-green algae. These "algal blooms" cause oxygen deficiency in the water, and fish die. A fish kill is a BIG wake up call that water quality is seriously dangerous. And...JORDAN LAKE IS OUR MAIN WATER SUPPLY, as well as the main water supply for many other municipalities in the Triangle area. Not to mention it that Jordan Lake brings over $16 million in tourism and is ranked in the top 10 destinations in NC! Chatham County would be extremely effected by a fish kill, in many ways.

So, are these wastewater systems safe? In areas that aren't so sensitive to nutrient loading -- maybe. Depends on some of the factors I mentioned above. Are they safe in sensitive areas, such as the protected and critical watershed areas of Jordan Lake (where water quality is already impaired and stakeholders are working on further measures of protection) -- NO. The fact of life is that problems with these systems are commonplace -- ask anyone who operates a wastewater system. This type of technology is good for some purposes, but there is absolutely NO evidence it is any safer when used in more dense cluster development than septic systems on larger lots. Period.

Finally, these systems don't have a long "life." They are expensive to maintain, and are still fairly "new." The long-term effects have yet to be realized.


Allison Weakley is a biologist

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Wastewater systems and the environment

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