Biomanipulating Diatom Growth – Ammonia and Cyanobacteria Reduction in Wastewater Treatment

Annual Conference

Management of ammonia and cyanobacteria in wastewater lagoons is historically problematic. Diatomix is a micronutrient solution, using nano-scale silica with ten micronutrients only bio-available to diatom algae. Dosing is determined by correcting the wastewater N: P micronutrient ratio to that of the Redfield Ratio.

Diatomix has been trialed over the last 2 years with several Australian Utility Companies in their wastewater treatment and storage lagoons. The addition of Diatomix in the wastewater treatment systems has reduced cyanobacteria cell count by 75% to 99.6% over 10 weeks to 19 weeks respectively. At one site, the average cyanobacteria cell count was 1,583,000 cells/mL prior to the trial starting and 197,000 cells/mL over the same period (April and May) the following year when treated with Diatomix. At a second site, the ammonia concentration averaged 20.6 mg/L prior to the treatment and eight weeks later it averaged 1.1 mg/L.

At the sites tested the average percentage of cyanobacteria cells in the Total cell count was initially 85 – 100% (cyanobacteria cells/Total cells * 100%). With treatment, this percentage reduced to between 22 and 99%. In the trial where there was minimal change in the percentage of cyanobacteria within the Total cell count, there was however a 78% reduction in the cyanobacterial cell count from 2,550,000 cells/mL to 566,000 cells/mL.

There is no sustained increase in diatom counts at any site and this is likely due to two main factors; Firstly, algal cell count sampling has been for suspended algae only, no benthic sampling. Secondly, diatom algae are heavily grazed by zooplankton and invertebrate populations. Over time as these grazing populations grow their feeding pressure on diatoms is likely to reduce cell counts. In regards to ammonia concentration, by optimizing the micronutrient to nitrogen and phosphorus ratio the diatom activity increases with higher uptake of ammonia.

Conference Papers

3.30 Biomanipulating Diatom Growth Ammonia and Cyanobacteria Reduction in Wastewater Treatment.pdf

pdf
831 KB
09 Nov 2017

3.30pm Dr S Tannock.pdf

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3 MB
09 Nov 2017