treatment includes: 

what is filtration? 

purpose and methods of disinfection

what is degassing? 

what is a simple screen? 

what is a rotary filter? 

what happens as water passes through rotary filter? 

what are the two rotary filter types? 

what are bag filters used for? 

what are bag filters made of? 

where are bag filters used? 

where are cartridge filters used? 

1. laboratory or hatchery systems 

what are particle filters? 

1. as water runs through bedding material, suspended materials are caught

what happens to the water flow when the bed material of particle filters gets smaller? 

1. smaller the suspended materials can be removed, but the slower the flow

what is backwashing in filtering? 

1. cleaning process to remove trapped particles 

why is backwashing important? 

1. essential to maintain the efficiency and lifespan of the filter

process of backwashing. 

1. flow of water is reversed to fluidize bed material (make solid particles behave like a fluid)

2. bed particles knock off adhering filtered material, backwash valve is opened

3. water with suspended material is pumped away

4. normal filtering is resumed

what does having multiple housing in filters impact function? 

1. greater efficiency, but requires more management

what are diatomaceous earth filters? 

1. fine powder that traps contaminants and particles in water

what kind of material are diatomaceous earth filters used for? 

1. very fine particles

what is another name for filter material in diatomaceous earth filters? 

1. “Celite”

steps of DE filters

1. pre-coat cycle: establish uniform cake of DE on permanent elements

2. continuous amount of DE introduced into water

3. service cycle: terminated when a pressure loss across filter is reached

4. system is put into a backwash / cleaning cycle

what are gravitational filters? 

1. gravity is used to separate out insoluble materials with a density greater than water’s

what is the relationship between density increase and efficiency of gravitational filters? 

1. positive relationship, as difference in density increases, efficiency of these filters increase

what is simple sedimentation? 

1. water is held still for hours to weeks 

2. gravity pulls sedimentation to the bottom, clearer water rises to the top

what should be added to simple sedimentation tanks to increase efficiency? 

1. a coagulant, for example, aluminum sulfate 

what do coagulants do for simple sedimentation? 

1. cause clumping, so sinking rate of sediment is increased

what is chitosan?

1. coagulant used for harvesting microalgae

2. is non-toxic

what kinds of coagulants are there? 

1. aluminum sulfate (alum)

2. chitosan 

what is centrifugation for filtering? 

1. increases the pull on heavy particles, which are pulled down through the water

what is efficiency a function of? 

1. rotational speed

2. centrifuge radius

3. rate water is flowing in 

4. the density of the suspended material

what is a hydroclone? 

1. uses centrifugal force to separate particles from liquid

what are the two major parameters of hydrocyclones? 

1. characteristics of the feed stream

2. geometry of the cyclone

what happens to liquid and sediment in hydrocyclone? 

1. lighter material (water) moves upward in the center, heavier material moves downward 

what are biological filters used for?

1. bacteria is used to remove nutrients or convert ammonia to a more oxidized state

what is an under-gravel filter?

1. filter material is always underwater

2. water is sucked through gravel on which bacteria live

what reactions occur with under-gravel filters and what does this mean?

1. oxidation reactions, so the water should have a high dissolved oxygen level

what is a trickling filter?

1. water is trickled over small stones

DO level of trickling filter

1. DO is never limiting

what is a drum? 

1. consists of series of rotating disks while partially submerged in water

what are fluidized bed filters / fluidized sand filters?

1. use suspended media to promote healthy bacteria growth

what kind of current do fluidized bed filters use? 

1. upwelling that passes through a medium, particles moving constantly

what is nitrification? 

1. conversion of toxic ammonia into less harmful nitrogen compounds

what do nitrification reactions require? 

1. DO

toxicity of ammonia and ammonium

1. ammonia is very toxic, ammonium less so

what happens to ammonium at higher pH values? 

1. ammonium shifts to ammonia

what does nitrosomonas do? 

1. oxidizes ammonia into nitrite 

2. uses energy gained through oxidation of ammonia to fix gaseous carbon dioxide into organic molecules

what does nitrobacter do? 

1. oxidizes nitrite into nitrate