Biological Process Questions Flashcards
Define aerobic processes
Process is undertaken by microorganisms that require oxygen for growth and metabolism.
Define anaerobic processes
Process undertaken by microorganisms without oxygen.
What are the advantages and disadvantages of anaerobic processes?
low nutrient requirements, low sludge protection, low space requirement and energy only needed for feed pump and circulation.
Disadvantage: not 100% COD removal and low growth rate of anaerobic process.
what is the sludge age?
Retention time of biomass in the system, with solid retention time SRT. The mass ratio of bacteria present in the aeration tank to the bacteria is removed daily with waste activated sludge.
What’s the difference between high F:M and low F:M?
High: high sludge protection, poor WWT and low O2 demand per incoming load
Low: Low growth rate, high WWT capacity and High O2 demand.
What are the 4 aerobic processes for suspended biomass?
Activated sludge process, Pure oxygen process, High depth and Sequencing batch reactor.
Explain Activated sludge process
Activated sludge - made up of an aeration tank and secondary clarifier, favors specific microorganisms by offering them an optimal environment to grow.
Explain High depth process
Reactor with high depth which creates a higher partial pressure for oxygen. This helps Henry’s law as a high partial pressure = high concentration of dissolved oxygen in the water = more efficient biological process.
What is SBR?
Sequencing batch reactor, where filling, stirring, aeration +reaction, sedimentation and removing all take place in a single reactor vessel. Has minimal footprint but risk of discharging sludge during the draw step.
What are the different aerobic processes for attached biomass?
Biofilm structure, trickling filter and fluidised bed
Explain Biofilm structure
Where bacteria attaches to the surface and its more resistant than suspended bacteria which is beneficial in the case of fluctuations.
What is a trickling filter?
Mechanical filtration of suspended solids, where there’s physical adsorption of dissolved compounds onto filter media.
What is a Fluidised bed?
Reactors with fluidised material. Has high energy needs and is a complex operation.
Why do we need to be careful with methane emissions from anaerobic processes?
Need to capture the bio-gas and not release it into the environment, as GHG potential of methane is 23 times higher than of Carbon dioxide.
How can we treat Biogas?
Treating bio-gas prior to use by removing H2S which is corrosive by adding some Fe. Also using a scrubber, biofilter or an activated carbon filter.
