Question

In: Civil Engineering

2. What are some organisms which might cause filamentous bulking (slow settling sludge) in activate

2. What are some organisms which might cause filamentous bulking (slow settling sludge) in activated sludge and what are some negative impacts of filamentous bulking? What are common mitigation measures for bulking activated sludge?

Expert Solution

Filamentous bulking refers to the slow settling of sludge in activated sludge process. It occurred when Food to Microorganisms ratio drop below 0.3 per day. It basically caused due to excessive growth of filamentous bacteria.

Nutrient condition in the wastewater system determine which bacteria is dominant. Some of the filamentous bacteria are:-

Nocardia spp., MicrothrixParvicella, Nocardia amarae, Nostocoida limicola, Alcaligenes paemba, Alcanivorax, borkumensis, Thiothrix spp, Sphaerotilus natans, Beggiatoa spp. and Haliscomenobacter hydrossis.

Some of the negative impact of sludge bulking are:-

Greater concentration of solid in effluent, greater BOD in

effluent hinder the settling of sludge particles, and reduces the overall efficiency of the whole process.

For control of sludge bulking, identification of filamentous organism that caused bulking is required. Than we can select any of the below method to control it:-

1. Short term measures:

Sludge Juggling

It basically involves return sludge (RAS) flow rate and waste feed points manipulation.

Solids must be removed from the final clarifier faster than they are added so the RAS flow rate must be iincrease.

Polymer and Coagulant Addition

Various types of chemicals are available which when added to activated sludge process, enhance the settling characterstics.

Chlorination

this is the most commonly used method. Chlorine and hydrogen peroxide proved to be successful in temporary control method for filamentous growth.

Please note that, if the bulking problem is not caused by filamentous bacteria, this method can worsen the bulking.

Long term measures

It includes activities such as:

control of influent waste septicity ; nutrient additions (mainly for industindu waste systems only); changes in aeration; and changes in biomass concentration .

Ally Wells answered 7 months ago

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