Microorganisms as Indicators of Water Quality

Overview

This laboratory investigation focused on identifying and classifying microorganisms commonly found in wastewater treatment systems. Through microscopy and comparative analysis, the study simulated real-world conditions where microbial communities serve as biological indicators of treatment plant performance and sludge health. Understanding these organisms’ ecological roles helps engineers optimize aeration, nutrient balance, and sludge retention times within activated-sludge processes.

Methodology

Samples were prepared on glass slides using a pipette and cover slip, then examined under a compound optical microscope equipped with a digital imaging system. Magnifications of 40x–1000x allowed observation of both metazoans and protozoa, with illumination and iris diaphragm adjustments to optimize contrast and resolution. Recorded images and videos were used to confirm identifications against published photomicrographs and literature sources.

Results

Distinct microbial species were observed across multiple samples, each offering diagnostic insight into sludge conditions:

Microorganism	Features & Behavior	Interpretation
Euglena	Green flagellate capable of photosynthesis and heterotrophy	Presence indicates high organic load or unstable conditions
Rotifer	Ciliated metazoan feeding on decomposing matter	Suggests mature sludge and healthy oxygenation
Vorticella	Bell-shaped ciliate attached to bacterial flocs	Found in systems with high DO and good settling performance
Blepharisma	Pink ciliate protozoan; predatory	Common under moderate to high organic load
Stentor	Trumpet-shaped protozoan, slow-moving	Sign of stable, low-BOD, oxygen-rich environment
Water Bear (Tardigrade)	Multicellular, eight-legged micro-animal	Indicates well-aerated, mature sludge with stable conditions

Reflection

This exercise bridged microbiology and process engineering, demonstrating how microscopic organisms reflect macro-scale operational efficiency. Identifying shifts from flagellate-dominated to rotifer-dominated communities mirrors transitions from young to mature sludge, guiding engineers in adjusting aeration and retention parameters. The experience also reinforced key microscopy skills, such as depth focusing, contrast management, and digital imaging documentation, which are practices directly applicable to real-world environmental monitoring.