Thursday, August 11, 2016

Sewage Spills And Algal Blooms

lake champlain no swimming signEvery year heavy rains in the Northeast cause wastewater treatment plants to reach and exceed capacity, with attendant overflows and sewage spills directly into lakes and rivers. Population growth, aging infrastructure and increased storm intensity are resulting in wastewater treatment plants legally allowing overflow of untreated sewage into waterways. This has included both raw sewage and graywater. Outdated and inadequate infrastructure (both public and private) are lending to the potential increase in toxic algal blooms and pathogens within the waters we drink from and recreate in.

When wastewater spills or is dumped into a body of water, it contains pharmaceuticals, synthetic hormones, pollutants and nutrients that can feed algal growth. There is an impact to the aquatic ecosystem from raw sewage or partially treated effluent that makes their way into our freshwater resources.

In most cases it is not the treatment process of a facility that is faulty, but the collection system and capacity. There is however a few treatment plants that have capacity but exceed effluent requirements, allowing nitrogen to leach into waterways. Excessive amounts of nitrogen can trigger toxic algal blooms. As wastewater treatment plants are regulated by the state, all overflow events are required to be  documented and reported. Regionally, sewage plants are in the process of upgrading and repairing identified issues. The upgrades and repairs to outdated infrastructure come with a hefty price tag.

Public wastewater treatment plants are not the only source of sewage making its way into waterways. The average lifespan of a properly maintained private septic system or onsite wastewater treatment system (OWTS) is 30 years. Failing or inefficient OWTS add excessive nutrients to our waterways feeding macrophytes (aquatic plants) and algae, causing excessive growth and nearshore algal blooms. Many camps and older homes near streams and lakes have old, undersized or inefficient OWTS. These can leach nutrients and other pollutants into surface water and groundwater.

Raw sewage is untreated septic from toilets. Graywater comes from showers, sinks and washers. Both contain nutrients that will feed algal growth. Raw sewage contains more nitrogen, while graywater contains more phosphorus. Depending on the body of water, the sewage spill has the potential of causing a cyanobacteria toxic harmful algal bloom.

Any algal bloom can alter water quality and have an impact to a body of water. As organic pollutant tolerant forms of algae dominate, they force out typical nutritional forms of algae that zooplankton and fish populations prefer. These same forms of algae can reduce sunlight that is needed for healthy macroalgae (Nitella sp) and macrophytes (aquatic plants) to grow. During the day an algal bloom will alter the pH of a water body and elevate the oxygen levels. At night the oxygen levels can plummet causing fish kills. Within the littoral zone, the excessive algal growth can smother feeding and breeding habitats for fish. Following an algal bloom, when the algae die and decompose, the bacteria that feed on them will deplete the oxygen causing hypoxic conditions. This can kill fish and other aquatic organisms

For more information on what you can do to properly maintain your wastewater treatment system, please contact your local watershed organization. For information on overflow spills from publicly owned treatment works and sewage systems, click here.

Photo courtesy Lake Champlain International.

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Corrina Parnapy, an Adirondack native  transplanted to Vermont with her husband and son, is the District Manager for the largest Natural Resources Conservation District in the State of Vermont.  She is the lead Aquatic Biologist/ Phycologist for Avacal Biological, and writes about the natural world for the Adirondack Almanack and other Northeast publications.

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