Investigation of the relationship between activated sludge floc shape information obtained from microscopic images and sludge properties
Hakoshima Suguru, So Kuroki, Tobino Tomohiro, Nakajima Fumiyuki
The University of Tokyo, Japan
Extended version recieved Excellent Poster Award at The 55nd Japan Society on Water Environment, 3/2021
Abstract
The activated sludge process is a widely used wastewater treatment process. In conventional operation and control of activated sludge processes, experienced-based management relying on information such as sludge characteristic indicators like MLSS and SVI, and component concentrations such as dissolved oxygen and ammonia has been conducted. However, with the remarkable development of information technology in recent years, advanced operation and management of wastewater treatment facilities utilizing information and communication technology is required. In this graduation thesis, the focus is on the shape of the activated sludge flocs. The shape of sludge flocs is believed to be related to the influent water quality, operating conditions, changes in internal microbial composition and activity, and potentially provide information that can be utilized for operational management. After obtaining multiple sludge shape indicators and evaluating their variations, the relationship between the obtained sludge shape indicators and sludge characteristics was examined.
The extraction flow of filamentous sludge
a. Original image
b. Image after binary processing and removal of small particles
c. Image after heatmap processing
d. Image with internal areas removed
e. Image with internal areas expanded
f. Composite image
g. Image with only filamentous substances extracted, noise removed, and holes filled.
Relationship between floc shape index and sludge properties
Mixed liquor suspended solids (MLSS) is a measure of the concentration of suspended solids, including microorganisms and other particles, in a mixed liquor sample from an activated sludge process. It is typically expressed in milligrams per liter (mg/L) and is used to monitor and control the performance of the treatment process.
Sludge Volume Index (SVI) is a measure of the settling characteristics of the mixed liquor in an activated sludge system. It is calculated by dividing the volume of settled sludge in milliliters by the grams of suspended solids in 1 liter of mixed liquor. SVI is used to evaluate the sedimentation performance of the activated sludge process and can indicate the presence of filamentous bacteria or other operational issues. A low SVI indicates good settling characteristics, while a high SVI suggests poor settling and potential operational problems.
Capillary Suction Time (CST) is a measure of the rate at which water is drawn from a porous material by capillary action. In the context of wastewater treatment, CST is used to evaluate the dewatering properties of sludge.