Chemical process questions Flashcards
Define reaction rate
Measure of change of concentration during a reaction, always positive.
What is the purpose of Aeration?
Aeration, typically first major process of treatment plant. It brings water and air in close contact for the removal of dissolved gases (CO2). Also oxidizes dissolved metals such as iron, hydrogen sulfide and volatile organic chemicals.
What is an anaerobic digester?
Energy efficient method, that uses anaerobic bacteria (biomass) to convert organic pollutants or COD into biogas in an oxygen-free environment.
What is the chemical equilibrium law?
Chemical system at equilibrium reacts to external changes in such a way that these changes are minimized. This leads to a new equilibrium.
What is a catalyst?
Increases the reaction rate by lowering the activation energy without being consumed.
What is a batch reactor?
Reactor with a stirrer which takes the final products out (plus the reactants that are left over) out of the WW. It’s discontinuous, no steady state and stirred tank.
What is a plug flow reactor
Initial concentration enters reactor and a disk/ slice moves through the reactor from front to back. It’s continuous, steady state and there’s no mixing between the slice of reactor.
What is a Continuous stirred tank reactor?
Same shape as the batch reactor. WW enters and is continuously taken out. It’s homogeneously mixed with the rest, so when the reaction takes place the concentration inside is the same that leaves and enters. It’s continuous and completely mixed.
What is the neutralization process?
The addition of acids or bases to wastewater in order to adjust the pH level to a neutral value (7). Thus prevents corrosion in WWT plants and sewers and protects the biological state and receiving waters.
What is the precipitation process?
The transfer of dissolved wastewater compounds into suspended ones by chemical reaction. Uses low solubility of metal hydroxides. The aim is to bring as much metal ions as possible into solid form.
Describe the multi-chamber system for coagulation.
1st mixing chamber for rapid mixing of the coagulants with the incoming wastewater so that the chemicals meet the colloids.
2nd flocculation chamber, to reduce the power of the stirring system. So a very gentle mixing for an hour.
3rd is the sedimentation tank, where WW is transferred and takes 90 minutes. The sedimentation of the Flocs will take place.
What is oxidation?
The oxidation element in a compound specifies the charge an atom would have if the electrons were completely on the side of an atom with the strongest electronegativity.
What’s the purpose of oxidation in WWT?
Applied in industrial wastewater treatment to transform inorganic substances into a more environmentally friendly compound, which can be eliminated. Can also be applied to organic substances to transform into a biodegradable substance.
