Andrew Fleming, Paul Sproules (Aquatec Fluid Systems) and Rodrigo Marquina (GV Water)
In 2020, after receiving odour complaints and discovering corrosion at a pump station in Shepparton, Goulburn Valley Water (GVW) trialled ozone dosing to mitigate these complaints and improve the asset. Aquatec was asked to deploy its OdoZone Mobile Diagnostic Unit (MDU), utilising on-site ozone generation designed to meet the foul air demand of the pump station.
Pump station SHPS21 is situated along a public roadside near an industrial building. Wet well corrosion was primarily due to the presence of organic-laden foul air in the incoming effluent from upstream industrial waste processes.
Aquatec’s OdoZone is an innovative alternative to traditional chemical dosing, in the form of oxygen/ozone dosing technology generated on-site, on-demand to mitigate odours. Ozone has a very high redox potential, and in breaking down odorous compounds, the by-products are predominantly oxygen and water. This system has a smaller footprint, less public disruption, and simplified WHS requirements compared with chemical dosing.
GVW initially commissioned a two-week trial in the peak of summer. In its first week, the MDU baselined H2S levels for later comparison, and in the second week, different dosing set points were trialled to gauge H2S removal effectiveness. The MDU’s effect on H2S levels was noticeable immediately.
GVW expanded the trial’s parameters for removal of other contaminants, and to assess the effect on downstream odour prevention. For a subsequent two weeks, the unit was tested against non-H2S odours, and its effect on the rising main which discharged six kilometres away was assessed.
Week one’s baseline data, compared to week two’s dosing, showed a 99.0% reduction of H2S levels (Figure 3). The unit was then turned off at midday each day, demonstrating odour would return to pre-dosing levels, and to prove that observed levels were not due to changes in sewer constancy.
Multiple gas grab samples were taken both during times of dosing and nondosing. Figure 4 shows average odour units while not dosing of 110,000 OU, comprising of predominately non-H2S contaminants.
During dosing, the odour level was reduced by 94.7% down 5,800 OU on average, proving ozone’s ability to reduce and oxidise both sulphides as well as other odorous compounds.
Lastly, as DO (Dissolved Oxygen) within the wastewater increased, the downstream effect of dosing at SHPS21 was measured at the downstream pump station (refer Figure 6 - average hourly H2S level at SHPS5). For the 36 hours prior to dosing the H2S levels were 53.6ppm (average) and 597.0ppm (peak). Once dosing recommenced, the H2S levels dropped to 4.5ppm (average) and 47.0ppm (peak); a 91.6% reduction.
OdoZone MDU Key Outcomes:
1. Eliminated public complaints
2. Effectively removed odour at SHPS21
3. Improved corrosion protection extending the asset’s expected life
4. Effective removal of odour and improved corrosion protection at receival point
5. Operational cost reduction compared to traditional chemical dosing
A collaborative approach to building a holistic odour profile enabled the most efficient and cost-effective mitigation strategy to be selected. In this case, this was an OdoZone system, which Aquatec have since installed at SHPS21 as a permanent unit.