Possible exam questions Flashcards
Why do we need to apply a PI (oxygen control) in the CSTR cascaded?
Because there are different ammonium concentrations in each tank, the first has a higher concentration and the last a low concentration. So less amount of Oxygen is consumed in the last reactors, leaving a higher SO that is not used. so for economical purposes, it’s necessary to optimize the amount of O2 in each tank.
What strategies can be done to mitigate a high concentration of SNO (Nitrate) in the effluent?
- Increasing the volume of the internal recirculation in the system
- Addition to external Carbon source to denitrification tanks
- With intermittent oxygen input (turning off aeration, converting nitrification to denitrification tank)
How can we control the inflow flow rate to the WWTP?
by buffering (storing) it or by bypassing it. Depending on the quality of the incoming water
How to control the amount of biomass in the Activated Sludge Tank (AST)?
By increasing the amount of return sludge from the secondary clarifier.
How do we determine that the steady state has been reached?
Looking at the Autotrophic biomass growth curve because they are the ones that take the longest time to reach the steady-state (slow growth rate)
Why do we need a cloosed loop aeration control (PI) in the dynamic simulation?
Due to the big fluctuations in the Oxygen demand during the day, the concentration of ammonium changes with time so the SO demand is changing as well, this leads to a high fluctuations, the closed loop aeration control regulates the amount of oxygen that is delivered to the tank according to the current demand
why is the liquor recirculated to the nitrification tanks?
The liquor coming from the thickeners contain high levels of ammonium SNH and Nitrogen that need to be treated. It can be input in the primary clarifier or in the AST
What is the purpouse of sludge treatment?
- Reduce the amount of solids in the water
- Biogas production
- Eliminate odors
- Inactivepathogens
- Nutrients and humus recycling
- Enhance dewatering processes
Why is important the sludge age in the digestor for the model used in SIMBA?
The digestor block in SIMBA classroom doesn´t consider the Anaerobic Digestor Model (ADM) (biological process). The biogas generated from this block is only based on the retention time of the sludge or sludge age and the flow (volume)
How to calculate the amount of biogas generated in the digestor in simba?
Simba digestor give us the theoretical methane produce per m3 (COD/m3) and we have to convert it to m3 of methane per day. using the stochiometric equation, the molar mass and the density of methane we can convert it
