Water Treatment Final

Goals from exam 1,2,3

Major Sources we use for drinking water

Surface water, groundwater

Benefits of surface water

Higher flows, more available volume, easier to access

Disadvantages of surface water

Easier to contaminate, higher total organic carbon, turbidity, pathogens

Benefits of groundwater

Lower flows, everywhere, natural filtration, low turbidity

Disadvantages of Ground water

higher total dissolved solids, hard to remediate once contaminated , source replenish low

Constituent categories

particulates, Biological (pathogens), Inorganic and organic chemicals

Particulates

Particles in the water, like clay, pathogens, living organisms

Dissolved Constituents

Minerals and chemicals like calcium, chloride, sodium etc

Gaseous Constituents

Carbon dioxide, nitrogen, ammonia

Major Physical characteristics to describe water

Turbidity, color, taste and odor

Natural organic matter (NOM)

NOM is produced from breakdown of plants and animals

Synthetic Organic Chemicals (SOCs)

industrial, agricultural, and municipal activities, like pfas, pesticides, etc

Specific Measurements

analyze a single constituent or property

Aggregate Measurements

broad water quality characteristics caused by multiple constituents

Chemical characteristics used to describe water quality

ph, alkalinity, tss, tds, toc

Turbidity

aggregate characteristic that describes the relative clarity of water, defines by light that is scattered

NTUs (nephelometric turbidity units)

units of measurement for turbidity

Alkalinity

measurement of waters quality to be able to resist changes in ph

TOC total organic carbon

aggregate characteristic for organic compounds, informs of organic contamination in water source. Often used to estimate NOM

Microbiological characteristics and measurments

for pathogens, indicator microorganism to measure. Ecoli is an example

Indicator microorganisms

presence indicates the potential for pathogen contamination, like total coliforms indicates for ecoli.

Primary Standard

legally enforceable federal standards for public drinking water, arsenic, barium, ecoli

MCL (maximum contaminant level)

highest concentration allowed in treated drinking water

MCLG maximum contaminant level goal

Aspirational or ideal level for water quality but not enforceable.

TT treatment technique

enforceable procedure or level of technological performance that public water systems must follow

Secondary Standards

Nonenforceable guidelines related to cosmetic, aesthetic, or technical effects. Color, fluoride.

SWTR

Surface water treatment rule, required systems to filter and disinfect Drinking water tanken from surface water sources

SDWA First amendment

1986, required epa act faster, enact requirements for disinfection and filtration, limit use of lead in drinking water pipes, monitoring hazardous waste injection near aquifers

Second amendment

1996, established CCL and UCMR, required accessible annual water quality reports, revoked 25 contaminants every three years

Process for regulating a contaminant under SDWA

Toxicity, exposure, necessity (sole judgement of the administrator)

CCL

Contaminant candidate list, list of known or anticipated to occur in public water systems that are not currently regulated

UCMR

unregulated contaminant monitoring rule, once every 5 years, list of contaminants on the potential CCL radar or in the news.

Milwaukee Cryptosporidium Outbreak

1993, water quality within regulation, unusually high turbidity, dosed new coagulant wrong leaving chlorine disinfection ineffective. Causing the second amendment of the SDWA

An anion commonly found in drinking water is:

Chloride

The most important general water quality parameter used to evaluate finished drinking water

Turbidity

Measuring pH is a type of:

specific amount

NOM is a concern in drinking water because

it can form disinfection byproducts

Lead and copper rules detail?:

The action levels for lead and copper at the tab

How are ph and pka related?

h and k are directly proportional

Carbonate System Equations

H2CO3 → HCO3 + H
HCO3 → CO3 + H

Equilibrium Equation

Ka = [H][OCl]/[HOCL]

Why is alkalinity good for drinking water treatment?

helps resist drastic pH changes when the system is perturbed by the addition of an acid/base

Coagulation

Addition of a chemical to condition the particles and dissolve substances for flocculation

Three options for coagulation?

Charge neutralization of the surface, particle bridging using charges polymers, sweep with metal salts

Metal salts

Alum, coagulation occurs by charge neutralization and sweep. Acidic and cheap

Prehydrolyzed salts

PACl, more resilient flocs, more expensive, lower dose needed, nonacidic

Organic Polymers

minimal pH effect, used with metal salts, expensive

Coagulant aids

sometimes not enough particulates in water for flocculation. usually uncharged inorganic particulates (clay) are added to increase turbidity.

Coag Selection based on Water Quality: High turbidity/ High Alkalinity

Best to work with, alum, ferric chloride. Polymers used with metal salts

Coag Selection based on Water Quality: High turbidity/ low Alkalinity

Prehydrolyzed metal for wider ph range bc it’s not acidic.

Coag Selection based on Water Quality: low turbidity/ High Alkalinity

Alum or ferric, coag aids required to inc turbidity

Coag Selection based on Water Quality: low turbidity/ low Alkalinity

Most difficult to work with, coag aid required. Metal salts with require neutralization

Coag Selection based on Water Quality: High NOM

ferric, alum, PACI in that order

why are jar test necessary?

determine the best coagulant, determine pH needed for optimal coagulation/floc, and determine optimal dose

Hydraulic Flocculation

Bafffled chamber, no power, small treatment plants, conventional filtration

Vertical Turbine

direct filtration (no sedimentation), easy to maintain

Horizontal Paddle

Most common, good for high influent turbidity, and large flows, more maintained and higher costs

Granular Filtration

Filtration romving constituents in water by passing it through a medium.

Granular filtration performance metrics

.3 NTU turbidity, 0 coliforms

Straining

Not dominant, for larger particles. most remaining flocs pass through however

attachment

small flocs attach to filter media