Water Quality & Pollution

Course Outline

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Water Quality & Pollution

Water Pollution: Its Sources & Effects

Human health effects

microbiological agents: the role of water in carrying disease was observed as far back as the early 1800s (before the existence of microbial pathogens was established) (Dr Snow took the handle off a pump on a public well in London)

viruses:

hepatitis

bacteria:

typhoid
cholera
salmonellosis (more common from food)
shigellosis (the commonly identified cause of bacterial acute diarrhea)

E coli caused diarrhea relatively rare

so called "H7" (type I157:H7) sometimes causes food-borne illness
can cause severe problems in infants

protozoa:

amoebic dysentery
recent outbreaks in Milwaukee of illness caused by Cryptosporidium
giardiasis (Giardia lamlia)

outbreaks in NW CT (unfiltered surface water supplies)
traditionally found in outdoors people
about 10x more resistant to chlorine than bacteria

schistosomiasis

a serious problem in Africa and other tropical regions
a microscopic parasitic trematode worm migrates from a freshwater snail host and penetrates the skin or mucus membranes of people wading in contaminated water

blood loss, tissue damage

poor planning makes the problem worse:

the waters of rivers which were once too swift to permit the growth of the host snail turn to prime breeding grounds after dams were installed (the impounded water is used for irrigation)

chemical pollutants

many types

heavy metals

arsenic
chromium
mercury: extremely toxic in the bioavailable methyl form; all mercury salts have some toxicity

inorganic toxins

cyanide-industrial waste
nitrates/nitrites-agricultural waste, sewage

organic compounds

chlorinated solvents
vinyl chloride
chloroform
hydrocarbons
oil
benzene
pesticides
PCBs

point vs non-point sources

a pipe (point)
a road, a field, a parking lot (non-point)

organic compounds

many occur naturally, these are primarily harmless
when water or wastewater is chlorinated, the chlorine (and to some extent it impurity bromine) react chemically with the natural organic matter and form "disinfection byproducts"; trihalomethanes and so forth that are carcinogenic

toxic pollutants regulated by the '77 amendments to the Clean Water Act

Priority Pollutants (list of orig 65, now 129 substances or classes of substances) included after '75 consent decree settlement of NRDC v.substances EPA

Effects on receiving waters

conventional pollutants: BOD, TSS, pH

Biochemical Oxygen Demand (BOD): a property of a wastewater roughly proportional to the amount of aerobically digestible organic matter it contains

as BOD is added to a receiving water, dissolved oxygen (DO) is consumed
sag curve: a plot of DO vs distance from discharge point

game fish require about 4 mg/L of oxygen (water at 65° saturated with oxygen has roughly 8 mg/L)
increasing temp decreases the amount of DO and increases basal respiration in aquatic orgs thereby increasing their oxygen req't

Total Suspended Solids TSS or SS

cloud water

reduce photosynthesis
looks bad

suspended sediment affects solubility & water chemistry
settles out damaging bottom habitat, reducing growth of shellfish and other organisms (including planktonic or benthic life stages of fish etc)

pH (acid/alkaline balance of water)

affects toxicity/solubility of metals
affect toxicity of metals
can be directly hazardous to aquatic life or disruptive of an ecosystem to the point of creating a dead zone (seen in acid rain affected lakes or lakes subject to acid mine drainage)

nutrients

N, P

Nitrogen is a big issue in Long Island Sound
Phosphorus is a big issue in Lake Champlain and Chesapeake Bay

promote algal growth

can speed up eutrophication
can cause nuisance blooms

toxic pollutants

known as the "Priority Pollutants" under the Clean Water Act
discharges may contain a known or unknown compound or combination of compounds that is/are toxic to aquatic life

CWA regs can require not just monitoring for specific toxic chemicals but actual bioassays for toxicity per se

The Great Lakes

conventional & toxic pollutants

eutrophication
bacteria
pesticides
industrial waste made Lake Erie a near dead zone in the 60s
canals etc have distorted the ecosystem dramatically

Drinking Water Quality

EPA and state agencies regulate drinking water

from Public Water Supplies = systems which supply:

15 or more connections at least 60 days/year
25 or more individuals at least 60 days/year
25 or more of the same nonresidents more than 6 months a year
Note: only residential systems required to meet all of the NPDWRs

regulations set maximum contaminant levels (MCLs)

call for monitoring and may specify types of treatment

Bacteriological aspects

illness caused by pathogens, usu introduced with the body waste of infected humans or other animals (either sick or carriers)

are not tested for directly

hard to grow
hazardous to have pure cultures of

coliform bacteria have been the indicator of drinking water quality since 1914

four genuses of bacteria including E coli, defined by their growth characteristics in the lab

all aerobic or facultative anaerobic gram negative non-sporeforming rods that ferment lactose to CO2 within 48 hours at 35°C
orgs that form dark pink colonies with a greenish-gold sheen in 24 h on mEndo at 35°C
orgs that cause a positive reaction (yellow color) in P/A test in 24 h at 35°C

associated with fecal waste, but not exclusively
correlated with the presence of pathogens

quality of bathing waters now determined using the test for Enterococci (a type of fecal streptococcal bacteria)

these organisms are highly correlated with risk of waterborne illness when found in the presence of other evidence of sewage contamination
fecal coliforms had been used in the past, total coliforms (and sometimes other orgs) still used in swimming pools

Chemical & Physical aspects

in addition to bacteriological standards there are also primary (ie health based) drinking water standards for turbidity (cloudiness), some metals and some inorganic and organic compounds
the standard for turbidity is due to concerns about effectiveness of disinfection and filtration; chemical standards are based on MCL goals

zero for cancer causing substances
no-observable-adverse-effect-levels (NOAELs) divided by 100 or 1000 margin of safety and normalized for a 70 kg adult drinking two liters of water per day

there are also secondary standards to insure that PWSs provide water which is palatable

W/Q Trends

surface water

W/Q, as damaged by point sources of pollution, has greatly improved as a result of the clean water legislation of the 60s and 70s

Great Lakes eutrophication reversed
Hudson, Potomac, Willamette and other rivers restored to some vitality

nonpoint sources and groundwater-mediated contamination remain a serious challenge
surface-water classifications:

AA =existing or potential public drinking water supply, fish & wildlife habitat, (potentially restricted) recreational use
A = potential drinking water, habitat, recreation, navigation
B = habitiat, recreational use (swimming, fishing)
C = degraded, goal is to upgrade to A or B, may not suitable for swimming
D = polluted to the point that habitat value and usefulness is impaired, goal is to upgrade (typically to B)
classification serves to guide planning

there are numerical and narrative W/Q standards for all classes
CT policy is to get all surface waters to class B or better

groundwater

important source of drinking water
CWA and similar legislation fairly bypassed groundwater; about 1% to 3% of GW is contaminated
there is a great variety of potential contaminants to groundwater; it can be degraded due to:

leaching from buried waste or stored materials
leaking from underground containers and pipes
runoff from roads, fields, and so forth
subsurface disposal of sewage or industrial waste
intrusion of saltwater

difficult to clean up once contaminated; concentration of pollutants in a small area can be quite high
ground-water classifications:

GAA = existing PWS source
GA = private drinking water or potential public drinking water
GB = presumed to be degraded, areas with water piped in; goal is either to improve or to prevent irreparable damage
GC = currently or potentially used for disposal within guidelines set out in the state's WQ Standards

Water Supply & Waste Disposal

Wells, springs & cisterns

although surface runoff is not safe to drink, groundwater is usually bacteriologically safe

loam, fine sand, or sand with clay or silt provides some "filtration" of microbes
residence time in the ground allows microbes to die off
coarse gravel, fractured rock may not allow sufficient filtration or die off for water to be safe
wells must be:

situated far enough from subsurface contamination (ie 75 feet from septic tank etc)
sealed to prevent the entrance of surface runoff

wellwater sometimes requires treatment to meet secondary (iron, pH) or primary (gasoline, solvents, bacteria) standards

Onsite septic systems

septic tank allows primary settling and some anaerobic (ie "smelly") digestion of solids and BOD (about 40% efficient)

sludge must be removed periodically

effluent still has high BOD, odor, pathogens, nitrate

drained to a leaching field

field must have adequate permeability (usu determined by percolation or "perc" test) to accomodate waste flow
entire system must sit above the water table (determined by observing mottling line)

if the site of a proposed septic system (ie, a building lot) does not have adequate topsoil or percolation, an "engineered" system is generally required

this system has special fill brought in to replace native material and regrade as necessary

failed system (eg clogged leaching field, etc) evidenced by waste appearing above ground, backing up

a well which is too close (within, say, 25 to 75 feet) may be contaminated even if septic system is working properly

Water Treatment

Public water supplies

as mentioned above, groundwater often requires no treatment; but may require treatment for:

corrosion control (raise pH and TDS)
iron or manganese removal
sulfide removal
removal of toxic organic chemicals or metals

surface water at least has to be disinfected

chlorine
ozone
ultraviolet light

often water is "filtered" or otherwise clarified

sedimentation:

alum (aluminum sulfate) is added to water and the pH is adjusted with lime or soda ash
the alum forms a loose precipitate or floc which binds other suspended particles and slowly settles to the bottom in specially designed tanks
organic polymers are sometimes added as well to increase efficiency
optimum conditions are determined using small-scale "jar-tests"

filtration:

slow sand filter
rapid sand filter:

often used in conjunction with sedimentation, the filter collects the floc making both processes more efficient
bed is layered to facilitate back-washing = the vigorous flow of water back through the sand bed to wash the filtered material off

the treated water is usually zapped with chlorine (post-chlorination) to kill off and remaining microbes

some organic matter makes it through, this can react with the chlorine to make chloroform etc
unfiltered water is more susceptible to this problem:

higher levels of chlorine are needed for dis'n and
higher levels of organic matter are present

other dis'n methods include ozone and UV

these tend to be more expensive and do not leave a residual disinfectent in the system

some areas need to desalinate the water

distillation
reverse osmosis

Water pollution control

sewage treatment: about 3/4 of households rely on municipal treatment plants

primary: coarse filtration and basic sedimentation

removes grit and settleable organic matter
about 30 to 50% efficient on SS and BOD

secondary

required by the CWA for all POTWs
two basic types:

activated sludge: aeration and recycling encourages the development of aerobic, settling microflora and microfauna in large aerated tanks
trickling filter: same idea but on a solid substrate (crushed rock, anthracite), typically some portion of effluent is recycled
sometimes both systems are used in parallel
in both types, some sludge is "wasted" ie disposed of

about 70-95% efficient in removing BOD, SS

tertiary

also called nutrient removal or polishing
designed to reduce P and N
lagoons, often with macroflora
mechanical contactor devices
chemical treatments
land application

sludge

so called solids removal is mostly solids settling
the volume of the resulting sludge can be reduced by digestion

anaerobic: primary sludge or dewatered secondary sludge stored in a digester where anaerobes convert the organic matter to carbon dioxide and methane (plus a little hydrogen sulfide)
the methane is often used to heat the plant and/or dry the secondary sludge

the digested sludge can be used as a soil additive, but around here it is typically landfilled (42% nationwide landfilled, 21% incinerated)

sewage treatment plants frequently receive industrial wastewater, hence the sludge is contaminated with heavy metals (but by law it is not considered to be a hazardous waste)

industrial waste

pretreatment standards are applied to industrial users of the POTW

prevent disruption of the plant
prevent flow through of pollutants not removed by the plant
prevent destruction of the sewer system
prevent hazards to the personnel
improve the quality of the sludge
waste must be pretreated to the levels dictated by the standards
direct discharges likewise must treat to certain standards
treatment often analogous to sewage treatment

chemical supplements or substitutes to biological/physical processes are sometimes used

Thermal pollution

water is diverted from a source, through some industrial process, then discharged
increase in receiving water temp can be lethal to fish etc
cooling towers/lagoons are used for control

these have their own problems:

evaporative consumption of water
concentration of salts etc through evaporation
water may have corrosion control agents added
increased fogging/icing

some blamed the killer fog ('92) on an interstate in Tennesee on a nearby papermill

Recycling

towns on the river are often recycling wastewater whether they like it or not
some direct, intentional recycling of reclaimed wastewater goes on

watering, irrigation
intensive treatment

River basin/regional planning

facilitated by funding in the old FWPCA (now the CWA)

necessary since water use, treatment etc in one part of a basin affects all users downstream

is being undertaken in an attempt to restore Long Island Sound

watershed includes all of CT, some of northern New England and the great sewage discharges of NYC
given the variety of political entities and interests it is a daunting task

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Course Outline

Environmental Studies

Environmental ET

Anthony G Benoit abenoit@trcc.commnet.edu
(860) 885-2386

Revised