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Influence of the nutrient balance on biofilm composition in a fixed film process
T L G Hendrickx1, E Meskus, R L Keiski
1Department of Process and Environmental Engineering, University of Oulu, Finland. tim.hendrickx@oulu.fi
Abstract:
An attached fungal growth has appeared in a fixed biofilm process at the waste water treatment plant of the City of Oulu, Finland. Due to the filamentous morphology of the fungi, biofilm support material is easily washed out. The appearance is believed to be the result of the unbalanced availability of nutrients, where phosphorus has been identified as the key component. Experimental work concentrated on the influence of phosphorus on the fungal growth. Bench scale experiments showed that a higher uptake of phosphorus for the removal of organic material is possible, which also resulted in a suppression of the fungal growth by bacterial biomass. The results were confirmed by experimentation in a full-scale biofilter. Addition of extra phosphoric acid to the biofilter influent resulted in a biofilm where the fungal growth is less pronounced. The fungal growth is believed to be competitive with the desired bacterial growth. It is possible to keep the fungal growth within limits by changing the conditions in favour of the bacterial growth, thus avoiding the operational problems connected with the filamentous fungi.
Insights
Excessive fungal growth in wastewater biofilms can be controlled by managing phosphorus levels. Optimizing phosphorus availability suppresses fungal growth, favoring beneficial bacteria and preventing operational issues in wastewater treatment.
Area of Science:
- Environmental microbiology
- Wastewater treatment technologies
- Biofilm engineering
Background:
- Filamentous fungal overgrowth in fixed biofilm processes disrupts wastewater treatment by washing out support material.
- This fungal proliferation is linked to nutrient imbalance, specifically phosphorus deficiency.
Purpose of the Study:
- To investigate the influence of phosphorus on fungal growth in wastewater biofilms.
- To determine if phosphorus management can control filamentous fungi and improve wastewater treatment efficiency.
Main Methods:
- Bench-scale experiments were conducted to assess phosphorus uptake and its effect on fungal and bacterial biomass.
- Full-scale biofilter experiments were performed, involving the addition of phosphoric acid to the influent.
Main Results:
- Increased phosphorus availability enhanced organic material removal and suppressed fungal growth, promoting bacterial biomass.
- Supplementation with phosphoric acid in a full-scale biofilter led to reduced fungal proliferation in the biofilm.
Conclusions:
- Phosphorus availability is a critical factor in controlling filamentous fungal growth in fixed biofilm wastewater treatment.
- Manipulating nutrient conditions to favor bacterial growth over fungal growth is a viable strategy to mitigate operational problems caused by filamentous fungi.