Microbiology 3050 Water Treatment

Examples of waterborne diseases

typhoid fever, cholera, and protozoan infections

Typhoid fever was a major …

public health threat before drinking water treatment

Cholera has had …

seven major pandemics since 1817, often occurs in areas with inadequate or no sewage treatment

Protozoan infections may be present …

in surface waters and may survive water treatment facilities as cysts because they can fit through filters and they are resistant to chlorine treatment

In the US we take …

drinking water for granted, a lot of countries don’t have water treatment systems, and we do a great job at purifying water

In the case of typhoid fever in PA, the use of filtration reduced …

cases by 90% and then the use of chlorination dropped that number even more

Why do we treat waste water?

Because the pollution can become dangerous, for example Cuyahoga river was so polluted that it caught fire, and Lake Hartwell has pcb’s from chemical plant dumps that make the fish who live near the floor toxic, other reasons: mediterranean and tourism, downstream users, and dead zones

What is a dead zone in the Gulf of Mexico?

an area of the ocean where bacteria are eating up all the available O2 when they break down massive amounts of algae that grow because fertilizer is washed off of farms into the ocean

The Mediterranean in some areas have signs that say not to …

swim because some even third world countries dump sewage straight into the ocean

It is polite to treat sewage water because it flows downstream, so …

all the people downstream from you will be stuck with whatever you put in the water

There are two types of water pollution:

Point sources such as domestic(like your house) and industrial, and Non-point sources like parking lots (oil gas, typical trash), feed lots (manure), agricultural fields (pesticides -DDT), golf courses and yards (chemicals used), and graveyards (embalming fluids)

What microorganisms pollute water?

bacteria, protozoa, and viruses

What is BOD?

Biological O2 demand, organic matter can pollute water and this is the demand of microorganisms needed to break down the organic matter

Nitrogen and Phosphorus can …

pollute water, and is plants are designed correctly, they can remove these from water (impressive)

Organic chemicals such as …

medicine or makeup can pollute water, they aren’t as common and are harder to remove because the bacteria used to break down things don’t encounter it as often

Inorganic chemicals that pollute water are often …

metals, plants do great with these because metals will bind to bacteria, then all you have to do is remove the bacteria

First in the water drinking treatment …

coagulation (forms and removes floc - insoluble material + microorganisms) to filtration (removes remaining particles, and most organic and inorganic compounds) to chlorination (kills remaining microorganisms and prevents growth of more) lastly storage

Activated C is used in …

filtration

Physical primary treatments include …

grates and screens, letting water sit it tanks (clarifiers) which removes 1/3 of BOD’s, separation of solids

Effluent still has …

substantial BOD

Secondary treatment comes …

from primary treatment, then its added to an aeration basin where organic matter is processed by suspended biomass, then it goes into a final clarifier where sludge is disposed (bacteria is used here to break down stuff)

In the secondary treatment stage we want little …

organic matter to bacteria ration because if the bacteria are starved they are sure to eat EVERYTHING that shouldn’t be in the water

Normal floc …

settles well (easy to separate)

Bulking sludge does …

does not settle properly

Tertiary treatment isn’t the 3rd step in water treatment which means …

it can be done at any time

Tertiary treatment includes …

Nitrogen and phosphorous removal

Nitrogen is present in sewage as …

ammonia (NH3) which is part of proteins

What converts ammonia to nitrate in aeration basins?

Nitrosomonas and Nitrobacter - called nitrification and this process consumes a lot of O2, about 60% of a plant’s energy is used to supply these bacteria with O2

What is the second step of nitrogen removal?

Nitrate to nitrogen gas (denitrification), N2 bubbles out of the wastewater, requires a special design of wastewater plant, beneficial because it reduces the energy needed for treatment

Nitrogen removal starts with …

water coming from the primary clarifier, to an anoxic basin where no O2 is present, this is where denitrification takes place and NO3 is used as the bacteria’s final e- acceptor instead of O2

After water goes through the anoxic basin, water goes to the …

aeration basin where O2 is present for nitrification (NH3 to NO3) this NO3 produced is then sent to the anoxic basin, then the water is sent to the final clarifier, some plants do UV and effluent after this

Phosphorous removal was discovered …

accidentally in South Africa 35 years ago, a group of bacteria called PAO’s (phosphorous accumulating organisms) will remove P under appropriate conditions, involves cycling between aerobic and anaerobic conditions

Phosphorous removal starts in …

an anaerobic basin where an e- acceptor isn’t present and BOD is removed, then it moves to the aeration basin where O2 is available and PO4 is removed then lastly a final clarifier and again UV and/or effluent

Wastewater disinfection can be done by …

chlorine or UV light

Chlorination involves …

gaseous chlorine which is dangerous because it forms carcinogenic chlorinated organics, however they are in extremely small amounts so it is (at least) currently deemed safe

UV light damages …

bacterial DNA and prevents bacteria from reproducing, if they don’t reproduce they won’t be detected in the MPN test

Chlorination leaves behind …

a residual in water that ensures bacteria don’t start growing when it leaves the plant and goes back to be used, why we like chlorination

Coliform detection method uses a standard method which …

uses MacConkey broth, EMB agar, nutrient agar, and doing a gram stain or using a membrane filter

Anaerobic digestion is used for …

high BOD industrial wastewater; it reduces the amount of sludge for disposal and produces methane, here bacteria will cannibalize each other - yay = less waste