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Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

Published on: September 26, 2016

Extracellular polymers in partly ozonated return activated sludge: impact on flocculation and dewaterability.

M A Dytczak¹, K Londry, H Siegrist

¹Department of Civil Engineering, University of Manitoba, Winnipeg R3T 5V6, Canada. umdytcza@cc.umanitoba.ca

Water Science and Technology : a Journal of the International Association on Water Pollution Research

|December 14, 2006

Summary

Partial ozonation of return activated sludge improved sludge settling properties by releasing biopolymers. While dewaterability was better in anoxic/aerobic conditions, ozonation

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Area of Science:

Environmental Engineering
Water Treatment Technologies
Sludge Management

Background:

Activated sludge settling and dewaterability are critical for efficient wastewater treatment.
Ozonation is explored as a pre-treatment method to enhance sludge properties.

Purpose of the Study:

To investigate the impact of partial ozonation on the settling and dewatering characteristics of return activated sludge.
To assess the influence of different reactor conditions (aerobic vs. anoxic/aerobic) on sludge properties post-ozonation.

Main Methods:

Sequencing batch reactors operated under aerobic and alternating anoxic/aerobic conditions.
Partial ozonation applied to return activated sludge at varying doses.
Sludge settleability assessed using settling kinetic studies and sludge volume index (SVI).
Dewaterability evaluated via capillary suction time (CST) tests.
Extracellular polymer substances (EPS) quantified using thermal-ethanolic extraction.

Main Results:

Ozonation released bound extracellular polymer substances (EPS), increasing soluble EPS fractions.
Increased food-to-microorganism (F/M) ratio in ozonated reactors enhanced flocculation and settling potential.
Alternating anoxic/aerobic conditions demonstrated superior dewaterability compared to strictly aerobic conditions.
Long-term operation showed minimal negative impact of ozonation on dewaterability.

Conclusions:

Partial ozonation can enhance sludge settling by altering EPS structure and solubility.
Sludge dewatering is significantly improved under alternating anoxic/aerobic conditions, beneficial for biological nutrient removal.
Ozonation presents a viable option for sludge conditioning with manageable impacts on dewaterability.