pubhtlh 264 - week 4: drinking water & waste water

sources of freshwater

• ground water (29.9%)

  • available at point of needs at little cost

• surface water 0,34

  • usually requires extensive purification

• ocean water (96.5%)

  • costly to desalinate

fresh water is an increasingly scarce resource due to…

• population growth

• change in water consumption pattern

• climate change

total water withdrawals by water-use category in the u.s. from 1950-2015

• rapid increase from 1950-1980

• slow decline after 1980

water pollution sources - point vs non point sources

• point sources: pollutants enter the waterways at well-defined locations (sewage treatment plants and industrial facilities’ waste pipe)

  • easier to control & monitor

• non-point sources: those which run off or seep into waterways from broad areas of land (agriculture, constructive activities, acid mine drainage, settling of air pollutants, landfill leachate)

  • harder to control & monitor

major drinking water contaminants

• pathogenic microbial

  • bacteria - cholera

  • viruses - hep A

  • protozoans - giardia lamblia & cryptosporidium

• chemicals

  • ingorganic contaminants - arsenic fluriode, lead, nitrates

  • synthetic organic pollutants - pesticides and herbicides, industrical solvents

  • disinfection by-products - tryhalomethanes

safe drinking water act (SDWA) 1974, 1986, 1996

• main federal law that ensures the quality of American's’ drinking water

• EPA established max contaminant levels for ore than 80 pollutants

  • criterria must be met by water supplied by community water system

clean water act

• main federal law that governs water pollution (ensure water is fishable & swimmable)

• 1972 amendments to Federal Water Pollution Control Act (1948) lead to the Clean Water Act

• Aim to restore and maintain the chemical, physical, and biological integrity of waters by preventing point and nonpoint pollution sources

water purification goal

provide safe source of water that meets wuality objectives at a reasonable cost

drinking water treatments/water purification process (top to bottom)

• raw water/drinking water source

• coagulation (chemicals added to neutralize the charge of dirt and dissolved particles), then flocculation (water is gently stirred to bind those paticles together into larger clumps called "floc")

• sedimentation (heavy floc particles sink)

• filtration (remove remaining small solids)

• disinfection (typically chlorine to kill pathogenic microorganisms)

• distribution system

5 water disinfection requirements

• Must destroy bacteria, viruses, and amebic cysts in water within a reasonable time despite all variations in water temperature, composition, and concentration of contaminants

• Must not be toxic for humans and domestic animals

• Must not be unreasonable in cost and safe and easy to store, handle

• Residual concentration in the treated water must be easily automatically determinable

• Must be sufficiently persistent so that the disappearance of the residual would be a warning of contamination

chlorine pros

favored disinfectant for water supplies because it is convenient, cheap, & residual

chlorine cons

• doesn’t kill protozoan cysts (plant) & some resistant viruses

• chlorine reaction by-products (unintended & harmful chemical compound)

  • may react w/ organic compounds to create disinfecton by-products (trihalomethanes)

  • surface water, high in dissolved natural organic material, are especially vulnerable to THM

  • THMS are potentially carcinogenic

ozone pros

highly effective against all types of microbes (bacteria, viruses, fungi, & protozoa (seed))

ozone cons

expensive, unstable (must be produced on-site b/c of short shelf life), high toxicity, create harmful by-products, highly complicated maintenance and operation, & no lasting residuals

uv radiation pros

very effective against bacteria, fungi, & protozoa (seed); no known formation of disinfection by-products

uv radiation cons

not so effective against viruses, no lasting residuals, & expensive

water fluoridation

• one of the ten great public health achievements of 20th century

• adjustment of fluoride concentration to 0.7 ppm to prevent tooth decay

why treat wastewater?

• carries pathogens & toxic chemicals

• low dissolved oxygen

• adds nutrients (nitrate & phosphate) to cause excessive algae growth

• increases solids or sediments in streams (turbidity increase aka murky water)

dissolved oxygen (DO)

• how much oxygen is "dissolved" in water & available for aquatic organisms to breathe; essentially the "breathable air" for underwater life

• if the bacteria use all the oxygen, the fish and other aquatic life suffocate because the DO levels become too low

oxygen sag curve

• Dissolved Oxygen (DO): amount of oxygen available for aquatic life. It drops sharply (the "sag"), which is bad, as bacteria consumed all of it to break down waste & none for aquatic life

• Biochemical Oxygen Demand (BOD): measures how much oxygen bacteria need to decompose the organic matter present. It is highest at the point of pollution and decreases as the waste is broken down.

why are nitrates & phosphates pollutants & the source?

• Eutrophication

  • Premature aging of aquatic system

  • Excessive nutrient level and excessive growth of algae eventually fills up a lake

• Source

  • Domestic sewage and animal sewage, fertilizer runoff, detergent

municipal sewage treatment

improve quality of wastewater so it can be discharged into a waterway w/o disrupting the aquatic envrionment or causing human health problems in the form of waterborne disease & not cause oxygen sag curve

water treatment process stages

• primary: physical & mechanical removal of solids

• secondary: biological process like bacteria to remove paticles that dissolved in the water

• tertiary: only required if the remaining 5% of contaminate need to be removed

  • Filtration

  • Removal of nutrients, such as nitrogen and phosphorus

  • Removal of other specific contaminants

  • Disinfection to destroy bacteria which can cause disease in humans

chlorination of treated wastewater concerns

• although chlorination before water discharge is standard, there are concerns because:

  • effective in killing bacteria but less so in relation to protozoans and viruses

  • chloramines are formed which may be toxic to aquatic life

  • expensive

technical issues related to pathogen detection

• impossible to monitor for all pathogens

• direct environmental pathogens detection from is technically demanding, often tedious, slow to produce results, sometimes unreliable, and expensive

  • low number of pathogens

  • human or non-human strains

  • pathogens difficult to detect cannot determine viability

  • need large sample volumes

  • fewer labs equipped or staffed day to weeks for results

Indicator organisms signal recent fecal contamination

• signal recent fecal contamination

  • Universally present in large numbers in warm blooded animal fecal materials

  • Readily detectable by simple methods

  • Do not grow in natural waters

  • Persistence in water treatment regimes is similar to that for pathogens

Microbal Indicators of Fecal Contamination

• Traditional approach to assess the sanitary quality of water with respect to fecal contamination

• Quantify bacteria commonly present in intestines of warm blooded animals

  • High numbers

  • Easy to measure

  • Surrogates for pathogens, especially bacterial pathogens

• May NOT be reliable indicators of viruses and parasites

Bacterial Indicators of Fecal Contamination in Water (think of picture)

• Total coliforms: standards for drinking waters

• Fecal (“thermotolerant”) coliforms: standards for wastewater effluents, biosolids, surface waters, shellfish harvest waters

• Eschrichia coli (E. coli): the “fecal” coliform; standards for drinking water

diseases related to water

• Water-borne diseases: cause by ingestion of water that are contaminated by 

  • Pathogenic microorganisms (choleria & typhoid)

  • Chemicals that have adverse effect on health (arsenic & pesticides)

• Water-washed disease: caused by poor personal hygiene and skin and eye contact with contaminated water (scabies, flea, lice, & tick-borne diseases)

• Water-based disease: cause by parasites in intermediate organisms living in contaminated water (schistosomiasis)

• Water-related diseases: caused by insect vectors, especially mosquitoes, that breed (malaria & dengue)

3 Water-borne Diseases

• Cholera

• Cryptosporidum

• Arsenic-associated disease

Cholera Epidemic in Soho, London 1854

when the pump handle was removed, no new cases were diagnosed in Broad Street

Cholera in Haiti, 2010

• This cholera epidemic appear to be the largest ever recorded in a single country during the past 50 years

• Outbreak worsened by earthquake: thousands homeless and destroyed sanitation and water infrastructure

1993 Milwaukee Cryptosoridium Outbreak

• their water and sewage system was connected

• Clinical manifestations included watery, diarrhea, adobminal cramps, fever, vomiting

extreme Precipitation and Water-borne Disease Outbreaks

• In Northern America, most documented waterborne disease outbreaks occur after extreme precipiation events

  • Rainfall: transport and dissemination fo infectious agents

  • Flooding: sewage treatment plants overflow; water sources contaminated, secondary shortage of clean drinking water

arsenic

• element in the Earth’s crust

  • No smell, no taste

  • Most arsenic compounds dissolve in water

arsenic compounds are classified as:

• inorganic arsenic (combined w/ oxygen, chlorine, or sulfur)

  • drinking water is a major exposure to inorganic arsenic

• organic arsenic (combines w/ carbon & hydrogen)

  • organic arsenic is usually less harmful than inorganic arsenic

other exposure pathways to inorganic arsenic

• Wood preservatives

• Electronics industry

• Manufacturing of copper and other metals

• Medicine

where in the u.s. are arsenic concentrations high

western states

health effects of arsenic (can mimic phosphate actions)

• Skin: Bowen’s disease

• Cancer: skin, liver, lung, kidney, bladder, prostate

• Non-cancer

  • Circulatory problems

  • Stocking & glove neuropathy (numbness)

  • Kidney damage

  • Keratosis, abnormal pigmentation, hair loss

  • nerve damage