Week 6 Part 3 - Microbiology of Enhanced Biological Phosphorus Removal (EBPR) in Wastewater Treatment

What is the primary cause of eutrophication in receiving waters?

Phosphorus enrichment

What are the two methods available for phosphorus reduction from wastewater?

1. Chemical removal with lime or alum 2. Microbiological using enhanced biological phosphorus removal (EBPR) system

What are the advantages of chemical removal of phosphorus with lime or alum?

Low initial cost, dose flexibility, ease of control, low energy use, low maintenance, reliable performance.

What are the disadvantages of chemical removal of phosphorus with lime or alum?

Increases sludge volume, high chemical costs, environmental damage, chemical sludge handling.

What are the advantages of biological phosphorus reduction?

Lower long-term costs, only biosolids produced, environmentally more acceptable, recyclable, higher reduction of phosphorus achievable.

What are the disadvantages of biological phosphorus reduction?

High initial costs, larger footprint, relatively higher energy costs, less reliable, potentially higher maintenance costs.

What is a common feature of all EBPR designs?

Alternating anaerobic and aerobic zones.

What is the Modified University of Cape Town Process?

A modification of the 3 Stage Phoredox Process used in EBPR.

What is the role of poly β-hydroxybutyrate (PHB) in the EBPR process?

PHB is synthesized anaerobically and utilized aerobically as a carbon and energy source for phosphorus assimilation.

Which bacteria are primarily associated with EBPR in activated sludge plants?

Acinetobacter spp., which belong to the Gram-negative Gammaproteobacteria.

What is the significance of Rhodocyclus-like bacteria in EBPR?

They are identified as PAOs that can assimilate acetate anaerobically to synthesize PHB and phosphate aerobically.

What are the two major groups of glycogen-accumulating organisms (GAOs) identified in EBPR?

1. Gammaproteobacteria - Candidatus 'Competibacter phosphatis' 2. Alphaproteobacteria - Defluvicoccus.

What conditions may allow GAOs to out-compete PAOs in EBPR systems?

Low dissolved oxygen (DO) and low acetate concentrations.

What is the role of 16S rRNA based clone libraries in studying PAOs?

They help identify dominant clones and design FISH probes to detect PAOs with desired phenotypes.

What is the importance of understanding the microbiology of phosphorus reduction?

It is crucial for controlling phosphorus levels in receiving waters and preventing eutrophication.

What is the fate of phosphorus when sludge is wasted in EBPR systems?

Phosphorus is removed from the system inside the biomass, contributing to biosolids.

What is the main challenge in identifying GAOs in EBPR systems?

They cannot be stained for glycogen inside bacterial cells, making identification difficult.

What is the metabolic process of PAOs under anaerobic conditions?

Stored polyphosphate is utilized by PAOs to provide energy (ATP) for assimilating readily biodegradable COD.

What is the metabolic process of PAOs under aerobic conditions?

PAOs utilize PHB as a carbon and energy source for phosphorus assimilation and synthesis of intracellular polyphosphate.

What is the significance of the TCA cycle in the EBPR process?

It is involved in the metabolic pathways of PAOs during aerobic conditions.

What is meant by 'biological phosphorus removal'?

A process where microorganisms are used to remove phosphorus from wastewater, typically in activated sludge systems.

What are the environmental impacts of phosphorus in receiving waters?

Phosphorus can lead to algal blooms, oxygen depletion, and overall degradation of water quality.

What is the role of acetate in the EBPR process?

Acetate serves as a readily biodegradable carbon source for PAOs during anaerobic and aerobic phases.

What are the characteristics of the biomass from anaerobic zones in EBPR?

Biomass contains poly β-hydroxybutyrate (PHB) but not polyphosphate (POLY-P).

What are the characteristics of the biomass from aerobic zones in EBPR?

Biomass contains polyphosphate (POLYP) but not PHB.

What is the significance of FISH (Fluorescent In Situ Hybridization) in studying EBPR?

FISH is used to visualize and identify specific bacterial populations within the biomass.