RESTORE Summer 2022:
Contribution of Septic Systems to Nutrient Contamination of Surface Waters.
Introduction
Septic systems are an onsite method of treating wastewater typically used in rural areas and places that do not have a treatment plant. The lack of wastewater infrastructure in small towns/municipalities makes a functioning septic system a good choice due to the low associated costs. In an ideal system, the wastewater discharge is given adequate conditions to properly remove the contaminants before it reaches the water supply. When septic systems fail or are tampered with, the contaminated wastewater can be released into the environment resulting in the pollution of surface water. This is becoming an increasing issue across Canada which can cause algal blooms and water hypoxia. The project aims to better understand the pathways of septic wastewater contamination.
Sampling Sites
Lake Erie Watershed:
The map indicates various sampling sites on the Lake Erie watershed used in this project. Many of these areas were known or thought to have septic systems inputs to streams.
Brownsville
Thamesville
Kingscourt
Walnut
Lake Simcoe Watershed:
Data was also collected around the Lake Simcoe watershed to further investigate the effects of septic wastewater contamination. The sites around the lake had different hydrogeological characteristics, household ages, and income levels. A wide variety of sites were chosen to investigate if there is a relationship between these various factors and septic contamination.
Photos were taken around various locations on Lake Simcoe.
Methods & Lab Analysis
Water samples and various water quality measurements like pH, dissolved oxygen, and electrical conductivity were recorded to better analyze septic pathways. At each of the sites, a velocity gauge was used in order to take readings and calculate the flow rate. Figuring out the flow helps to accurately understand how quickly nutrients, as well as septic wastewater, are moving through the streams.
Rain event and high flow sampling were also conducted to see if any concentrations within the stream changed under varying conditions.
A variety of lab procedures were done to test for indicators of septic wastewater such as phosphorus, human DNA markers, E.coli, and acesulfame. Finding one of the indicators on its own does not necessarily mean there is septic contamination. Phosphorous and E.coli may be present from sources other than septic systems, so analyzing them along with acesulfame and the DNA markers is a more accurate evaluation of a stream.
Acesulfame
An artificial sweetener that is heavily used in products consumed and used by humans. Easily detectable in the environment and may indicate evidence of septic wastewater.
DNA Markers
HF-183 is a human DNA marker that provides a tracer for septic wastewater.
E.coli
A common type of gut/intestinal bacteria in humans and a variety of different animals.
Phosphorus
Many types of phosphorus naturally exist within the environment but can also be increased via surface water runoff. Septic systems may also add excess phosphorus from organic waste entering streams.
E.coli Testing
Water samples were pumped through filter paper to collect the E.coli. Then they were placed into a petri dish of agar, which provides nutrients for the E.coli to grow.
Petri dish before and after incubation. The E.coli was typically put in the incubator for 20-22 hours at 44.5 degrees Celcius.
Next Steps:
The septic system project will continue to collect more data from all of the various sampling locations. Seasonality has different effects on stream conditions, for example, summer base flow versus a spring melt. Additional samples and measurements obtained throughout the year will provide a more accurate data set to draw conclusions and results from.
