Fate of return activated sludge after ozonation: an optimization study for sludge disintegration
1The Graduate School of Natural and Applied Sciences, Dokuz Eylül University, Buca-Izmir, Turkey. ozlem.demir@deu.edu.tr
Environmental Technology
|December 18, 2012
Summary
Ozonation effectively disintegrates sludge, reducing solids by over 70% at an optimal dose. This process releases nutrients and alters sludge properties, impacting dewaterability and filterability for wastewater treatment.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Wastewater Management
Background:
- Excess sludge production is a significant challenge in biological wastewater treatment.
- Ozonation is explored as a pre-treatment method to enhance sludge disintegration.
- Optimizing ozone dosage is crucial to balance effectiveness and cost while avoiding treatment inhibition.
Purpose of the Study:
- To investigate the effects of ozonation on return activated sludge disintegration.
- To determine the optimal ozone dose for sludge disintegration, minimizing cost and inhibition.
- To evaluate the impact of ozonation on sludge characteristics, including solids, nutrient release, dewaterability, and particle size.
Main Methods:
- Return activated sludge was subjected to ozonation at seven different ozone doses.
- Sludge and supernatant characteristics were analyzed, including suspended solids, volatile suspended solids, total nitrogen, and total phosphorus.
- Dewaterability and filterability were assessed using capillary suction time and specific resistance to filtration.
- Particle size distribution was measured to evaluate floc disruption.
Main Results:
- An optimal ozone dose of 0.05 g O3/gTS was identified for effective sludge disintegration.
- At the optimal dose, suspended solids and volatile suspended solids decreased by 77.8% and 71.6%, respectively.
- Ozonation significantly decomposed sludge flocs, leading to a substantial increase in supernatant total nitrogen (7 to 151 mg/L) and total phosphorus (8.8 to 33 mg/L).
- Dewaterability initially worsened (increased capillary suction time) but specific resistance to filtration decreased significantly after reaching a peak.
Conclusions:
- Ozonation is an effective method for sludge disintegration, reducing solids and releasing nutrients.
- The optimal ozone dose of 0.05 g O3/gTS balances disintegration efficiency with cost and potential inhibition.
- Ozonation alters sludge floc structure, impacting dewaterability and filterability, which requires further consideration in treatment process design.
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