Dayboro Wet Weather Storage Dam

(not documented)

(not documented)

Council

On-ground work

(none)

Unitywater OPEX

$12,000

(not documented)

20 May 2015

Ongoing

The use of Diatomix in this wet weather storage for wastewater effluent was to reduce the growth of Blue-green algae (BGA - Cyanobacteria). The pH had been consistently increasing over five years as a result of bloom after bloom of BGA.  Poor water quality can reduce the uses for the water as well as the times when it can be released.

Funding amount for this project is provided on an annual basis.

The use of Diatomix will reduce the nutrient profile of the water, lowering the concentrations of ammonia, nitrate and orthophosphate.  The increased growth of diatom algae, boosted by Diatomix micronutrients, means diatoms need more nitrogen and phosphorus and this is the cause of the nutrient reductions.  By creating consistent diatom algae growth, this in turn will provide a food source for the higher levels of the food chain.  This means that the nitrogen and phosphorus moves from dissolved inorganic nutrient into biologically bound nutrient that cannot feed weeds, other algae and cause eutrophication downstream.

The nutrient levels began to reduce in the first week and continued to do so.  The increased growth of diatoms reduced the pH of the water over several weeks.  This is unexpected from an algal growth that is commonly associated with pH increase.  The reason the pH reduced is due to the associated increase in the higher trophic levels of zooplankton, invertebrates, macroinvertebrates, gastropods, eels, fish etc.  The addition of CO2 from animal respiration would reduce pH.
As well as the changes to the concentrations of ammonia and nitrate, there was a change to the ratio of ammonia and nitrate.  Initially there was little to no nitrate in the system and this reflects a lower level of dissolved oxygen, and a limited activity of aerobic bacteria to nitrify ammonia (NH3) into nitrate (NO3-). 
Over time, the clarity of water has increased as the types of algae grown in the water have changed from suspended algae into benthic or periphyton algae (particularly diatoms) that grow in biofilms on surfaces in the water (e.g. twigs, leaves, reeds and rushes).  The increased water clarity assists in UV light reaching deeper into the water and reducing pathogenic bacteria.
As well as the changes to the concentrations of ammonia and nitrate, there was a change to the ratio of ammonia and nitrate.  Initially there was little to no nitrate in the system and this reflects a lower level of dissolved oxygen, and a limited activity of aerobic bacteria to nitrify ammonia (NH3) into nitrate (NO3-).

(none)