Term Test 2 - Water Quality Control

Total Dissolved Solids

a solid residue that remains in the water after filtration

Sources of Total Dissolved Solids

Minerals, metals, gases, vegetation decay

Impacts of Total Dissolved Solids

• Bad taste/odor/appearance

• Toxic chemicals

• Aggressive unsaturated water

Alkalinity

a measure of the ability of water to neutralize acids

Most common constituents of alkalinity

Bicarbonates, carbonates, hydroxide

Impacts of alkalinity

Bitter taste, alkalinity + cations in water = precipitate

Hardness

• the concentration of multivalent metallic cations

Hardness may be represented by the sum of

calcium and magnesium ions

Sources of hardness

Calcium, magnesium, iron, manganese

Impacts of hardness

Boiler scale fouling

Soap scum

Carbonate hardness is equivalent to the

alkalinity

Carbonate hardness is sensitive to

heat

Magnesium hardness effect to those unaccustomed

Laxative

How much hardness does the USA Public Service recommend in water?

A maximum of 500 mg/L

What does microbial decomposition of organics in anaerobic environments result in?

Unstable and objectionable end products

Nitrification - Denitrification Process

Ammonia → Nitrite → Nitrate

Nitrogenous biochemical oxygen demand

The oxygen demand associated with the oxidation of ammonia to nitrate

How many days does it take for nitrifying bacteria to reach significant numbers?

6 to 10 days

Carbonaceous biochemical oxygen demand

The oxygen demand resulting from the decomposition of organic carbon compounds in water.

What organic materials are resistant to biological degradation?

Tannic and lignin acids, cellulose, phenols, some polysaccharides, benzenes, surfectants

How are non-biodegradable organics measured?

Chemical oxygen demand test, total organic carbon analysis

Process of COD

Uses potassium dichromate

Used to treat industrial/municipal wastewater that have compounds toxic to biological life

Determined in 3 hours

TOC

Tests small concentrations of organic matter

Organic carbon is oxidized to carbon dioxide

Hydrologic cycle

the continuous movement of water in the environment, from rainfall to runoff to percolation to evaporation/transpiration

Transpiration

plants absorb water from the soil and release it to the atmosphere through their leaves

Evaporation

water becomes vapour

Evapotranspiration

the combination of evaporation and transpiration

Temporary or carbonate hardness can be removed by

heat

Total hardness

the sum of calcium and magnesium hardness

HCO3 anions hardness is called

carbonate hardness

NCH is defined as total hardness in

excess of the alkalinity. If the alkalinity is equal to or greater than the total hardness, there is no NCH

Aquiclude

a low permeability geologic unit that forms either the upper or lower boundary of a groundwater flow system

Typical aquiclude material

Clay

Aquifer

A geologic formation that is saturated and permeable enough to transmit quantities of water to wells and springs

Aquitard

Low permeability geologic unit that can store groundwater

Piezometric surface

the level to which water will rise in an aquifer under natural conditions. In a water table aquifer, the piezometric surface is the water table level. In a confined aquifer, the piezometric section may be significantly above the top of the rock formation

Hydraulic conductivity

a measure of the ease with which fluid is transported through a porous rock

Steady flow assumes

uniform withdraw, a stable drawdown curve, laminar groundwater flow, homogenous isotropic aquifer

Preliminary processes of water treatment

Bar screens or racks - retain floating debris

Communitor - mechanical cutting/shredding device

Grit removal - removal of things like sand, coffee, eggshells using grit chambers

Primary treatment

The combination of preliminary processes and gravity settling

Wastewater’s organic solids can be removed by plain sedimentation or gravity settling

After grit removal, wastewater is transferred to primary clarifier

Primary clarifier detention time

1 to 2 hours

What does a primary clarifier do?

• Scrapes the settled solids along the bottom to a sludge hopper

• Surface slimming device is used to remove grease

• Chemical coagulant is added to remove particles

How much of the Total Suspended Solids and BOD can be removed from the wastewater from primary treatment?

60% of the TSS, 35% of the BOD

Secondary treatment

• Purpose is to remove the suspended solids that did not settle out on the primary tanks and dissolved BOD that is unaffected by physical treatment

• Use of microorganisms that take place in artificial environments like concrete tanks

• Bacteria and protozoa consume the organic pollutants

Trickling filter

A method of secondary treatment that uses microorganisms attached to a media to degrade organic matter in wastewater as it flows over the surface.

• layer of crushed rocks about 2m deep

• Primary effluent is sprayed over the surface

• It causes biofilm to develop on the surface

• Removes oxygen demanding substances from the wastewater

• When it gets thicker, wastewater washes it off the surface, which is called sloughing

Activated sludge process

Utilizes aeration tanks where microorganisms digest organic pollutants in wastewater, resulting in treated effluent.

Sloughing

Wastewater washing biofilm off the surface after a trickling filter is used

Supernatant

The liquid that remains above the sediment after a sample has been centrifuged or allowed to settle, typically containing dissolved and suspended substances.

F/M Ratio

Food to microorganisms ratio

Mixed Liquor Suspended Solids

The concentration of suspended solids in a mixture of water and microorganisms, often used in wastewater treatment to assess treatment performance.

Sludge bulking

A condition in wastewater treatment where sludge settles poorly due to excessive growth of microorganisms

How can sludge bulking be controlled

by optimizing aeration, reducing nutrient loading, and maintaining appropriate F/M ratio to manage microorganism growth.

What does tertiary treatment consist of?

Removal of phosphorus and nitrogen

How is phosphorus removed?

Chemical precipitation of ions and coagulant (alum)

How is nitrogen removed?

by biological processes or nitrification-denitrification

Ammonia stripping

• Ph is raised to convert ammonium ions (NH4) to ammonia gas (NH3)

• Wastewater goes down tower, letting ammonia gas escape