Meeting papers

                                                                                      Burgess Creek
                                                 Receiving Environment Monitoring Program
                                                                                 Annual Review 2022
result in the accumulation of detrital matter, algae (as evidenced by high chlorophyll-a levels),
and anaerobic processes. Groundwater also contributes to Burgess Creek, which receives
substantial input from various sources such as large sand masses and undulating landscapes
(Department of Environment and Science, 2018).

Statistical testing of individual parameters showed minimal change in water quality at most
monitoring sites between 2020 and 2021, with only three significant differences detected from
a total of 105 Students' t-tests performed. Of these three differences, two were statistically
significant increases, DO at B5 and pH at B2. The statistically significant decrease was total
nitrogen at B2 an upstream site not influenced by treated wastewater. Typically, improved
treated wastewater is more likely to lead to increased pH and dissolved oxygen (DO) levels in
water bodies. This is because improved treatment processes remove more organic matter
from wastewater, which reduces the amount of oxygen that is used up by bacteria during
decomposition and lowers the concentration of organic and inorganic acids. The design of the
Noosa STP includes an inverted bell mouth, which facilitates the release of treated wastewater
into the receiving environment with high concentrations of dissolved oxygen. This helps to
compensate for any oxygen demand created by the presence of nutrients in the wastewater,
reducing the risk of oxygen depletion and negative impacts on aquatic life. As a result, more
oxygen is available for aquatic organisms, which can lead to increased DO levels. On the other
hand, poor treated wastewater, which contains higher levels of organic matter, can lead to
lower DO levels as the organic matter decomposes and depletes oxygen levels in the water,
which has not been observed within this dataset.

In 2021, the Burgess Creek water quality objectives had the best overall compliance
percentage recorded to date. The monitoring sites not influenced by Noosa STP inputs, such
as upstream reference site B8 and east branch site B2, maintained the highest overall
compliance with the prescribed objectives. While some downstream monitoring sites
experienced a slight increase in compliance compared to 2020, one site, B3 at the outfall, had
an overall decrease of 4%. Nevertheless, the catchment as a whole improved, with the
percentage compliance increasing from 46% in 2020 to 49% in 2021.

A comparative assessment against biological indicators with Australian and New Zealand
guidelines for fresh and marine water quality demonstrated 100% compliance of E.coli for all
sites except for B1 and SW3. Monitoring site B3 demonstrated 100% compliance with
thermotolerant coliforms and enterococci and B2 was also found to be 100% compliant for
faecal coliforms. Elevated microbiological concentrations at the mouth of Burgess Creek is not
considered attributable to Noosa STP given concentrations in the Catchment upstream are

  This document may not, in whole or part, be copied, photocopied, reproduced,
  or translated without prior consent from the CEO, Unitywater.                     Page 53 of 64

                                                                                            Page 163 of 215