Algae treatment

Algae treatment — Key considerations

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• Overview
• Key considerations
• Planning and design
• Construction and operation
• Links and references

What makes an effective algae treatment system?

• Constant water flow (does not cope with drying out).
• Shallow, raceway construction with mechanical mixing to maximise sunlight exposure[5].
• Species of algae should be effective in trapping the target pollutant and should occur locally[4][3].
• Bypass for flood flows[2].
• Requires a sand filter or sediment pond to capture sediment prior to water entering the algal treatment system (turbidity significantly impacts algae productivity)[2].
• Algae is generally more productive with higher nutrient concentrations (i.e. Oedogonium sp. was most productive between 2-20mg/L DIN and low DIN of 0.2mg/L reduced growth)[4].
• The system should be sized appropriately to treat expected inflows and have a high flow bypass for flows exceeding the treatment capacity[5].
• Detention time - A water exchange rate of 0.1 to 2 pond volume per day is optimal (therefore, the detention time is 0.5-10 days) depending on the macroalgae species and nutrient flux[1][5].

Treatment processes

Suitability and limitations

The technology has been applied to aquaculture, sewage treatment plants and industrial waste streams[2][6]. Different macroalgae species can be selected for treating freshwater or saline water, so it is particularly relevant to land-based marine aquaculture.

The treatment system may be applicable to agricultural stormwater runoff or irrigation tailwater where regular flows are available and the system is appropriately designed with a high flow bypass for storm flows[5][2].

The capacity of macroalgae to treat irrigation tailwater from sugar cane has been trialled in a laboratory. This included testing the effects of added diuron (photosystem II inhibiting herbicide used in sugarcane production) as might be present in sugarcane runoff/tailwater to test whether the macroalgae treatment systems could effectively operate in the presence of this herbicide. The algae trialled (Oedogonium sp.) survived, with reduced productivity, when diuron concentrations were 10µg/L, however diuron concentrations of 30μg/L were lethal[3].

The cost-effectiveness of algae treatment in removing the target pollutant/s needs to be considered relative to other treatment structures. Refer to cost considerations for more information.

References

1. ^ Cole, AJ, de Nys, R & Paul, NA (2015), 'Biorecovery of nutrient waste as protein in freshwater macroalgae', Algal Research, vol. 7, pp. 58-65.
2. ^ a b c d Lawson, A (8 July 2016), 'Bioremediation using freshwater algae', Treatment Systems in Coastal Catchments Forum. [online] Available at: https://wetlandinfo.des.qld.gov.au/wetlands/management/treatment-systems/for-agriculture/treatment-sys-nav-page/treatment-forum/.
3. ^ a b Lawton, R (2015), Reduction of nutrient loads in sugarcane run-off water through algal bioremediation, MACRO — the Centre for Macroalgal Resources and Biotechnology, James Cook University, Queensland.
4. ^ a b Lawton, RJ, de Nys, R & Paul, NA (2013), 'Selecting Reliable and Robust Freshwater Macroalgae for Biomass Applications', PLoS ONE, vol. 8, no. 5.
5. ^ a b c d Rickert, A & McShane, T (2015), Remediation of Agricultural Irrigation Runoff Using High Rate Algal Ponds: A feasibility study. [online], Burdekin-Bowen Integrated Floodplain Management Advisory Committee (BBIFMAC). Available at: https://pdfs.semanticscholar.org/a8ec/e93a4ae3742d9d70f9c1093e59044f6fec21.pdf.
6. ^ Roberts, DA, Paul, NA, Bird, MI & de Nys, R (2015), 'Bioremediation for coal-fired power stations using macroalgae', Journal of Environmental Management, vol. 153, pp. 25-32.

Last updated: 30 June 2022