PUBH 415 Midterm
Know the drinking water treatment process
1. Coagulation and flocculation 2. Sedimentation 3. Filtration 4. Disinfection 5. Storage
The BOD TEST is carried out by:
1. Diluting the sample with pure water saturated with oxygen. 2. Inoculating it with a fixed amount of bacteria. 3. Sealing the sample and then placing it in the dark for 5 days at 20C. 4. Measure unused dissolved oxygen (DO).
HIERARACHY
1. Source reduction and reuse § Source reduction - the best and cheapest way of managing waste is not to produce them in the first place. § Examples · Reducing the weight of items (steel cans are 60% lighter than they used to be) · Designing products to last longer and be easier to repair · Reducing paper waste via. Electronic communication, data transfer, the internet. · Buy selectively § Reuse (Reusing products >> recycling) · Use reusable items instead of single-use items. · Reuse by repairing broke products rather than replacing them with new products. · donate used products
HIERARACHY cont.
3. Energy Recovery 4. Treatment and disposal
Categories
Agricultural - 51%. Mining - 38%, industrial - 8%, municipal 3%
Chloramines
Chloramines DO NOT MIX!: produce less DBPs than other chlorine chemicals.
Corrosivity
Corrosive wastes are materials, including solids, that are acids or bases, or that produce acidic or alkaline solutions. Aqueous wastes with a pH less than or equal to 2.0 or greater than or equal to 12.5 are corrosive. A liquid waste may also be corrosive if it is able to corrode metal containers, such as storage tanks, drums, and barrels. Spent battery acid is an example.
BOD TEST Question
If something uses a lot of dissolved oxygen that means the bacteria has a lot of food, what does the bacteria have a lot of food from? Contamination, organic matter, nitrate, phosphate. Food for the bacteria, so they consume the oxygen so the biochemical oxygen demand is high it depletes the dissolved oxygen, that means if you have a BOD test that is a high BOD test, meaning it uses the known quantity of oxygen, then that is a contaminated water source
Characteristic Hazardous Waste - 4 characteristics
Ignitability Corrosivity Reactivity Toxicity
Ignitability
Ignitable wastes can create fires under certain conditions, undergo spontaneous combustion, or have a flash point less than 60°C (140°F). Examples include waste oil and used solvents.
Used Oil :
In California, waste oil and materials that contain or are contaminated with waste oil are usually regulated as hazardous wastes if they meet the definition of "Used Oil" even if they do not exhibit any of the characteristics of hazardous waste
Reactivity
Reactive wastes are unstable under normal conditions. They can cause explosions or release toxic fumes, gases, or vapors when heated, compressed, or mixed with water. Examples include lithium-sulfur batteries and unused explosives
how septic system works vs. municipal waste water treatment system
Septic system gets waste water from thousands of people and treats it all from bulk and then the waste product and wastewater from in today's world in OC further treated to reclaimed water, basically recycling water.
Storm drain
Storm drain will go to the river/the bed and then wash and flush into the ocean, it's called first flush is when the first rain fall happens. And when you are driving your car and you're are slipping. All that oil, on the road, gets lift up and its less dense than water and it goes straight to the storm drain and where it goes to? The ocean! Called FIRST FLUSH! Multiple choice question! And then problems with storm water pollution if you are on your lawn and you put too much fertilizer before rainfall, that rainwater carries right into the storm drain into the gutter and where the gutter goes to? The storm drain! And you got eutrophication. It happens every year because in the Gulf of Mexico there is a huge river and where does the river get all the storm flow from? From all the farms and discharges and all of the domestic sources of nitrites and phosphates and they make their way into the river. And we get it every year, eutrophication, but only part of it in Gulf of Mexico and it causes red rides causes certain problems, and you want to remember what harmful algae blooms are and what they do and how they are hazardous and toxic. Where does it occur? Every single year? It occurs in the Gulf of Mexico (midterm question!!) which causes eutrophication in an unknown area, and you get certain bacteria and it changes the way we harvest fish, clams, oysters. Need to make sure they are pasteurized to get rid of the bacteria.
Toxicity
Toxic wastes are harmful or fatal when ingested or absorbed (e.g., wastes 3 containing mercury, lead, DDT, PCBs, etc.). When toxic wastes are disposed, the toxic constituents may leach from the waste and pollute ground water. It contains eight subsections, as described. A waste is a toxic hazardous waste if it is identified as being toxic by any one (or more) of the eight subsections of this characteristic (remember coffee, and review aquatic toxicity) Lead is toxicity.
true or false: Water from the State Water Project is more reliable because it's in a greater rainfall area.
True
Water table
Water table o When the water table is lowered, there is less water (pressure) to push out salt water, which results in salt water intrusion. o High water tables maintain pressure in the aquifers § Freshwater flows into the ocean and wells near the ocean yield fresh water. o Lowering the water table reduces pressure, resulting to salt water flowing into the aquifer and contaminating coastal area wells.
Know the three Rs (reduce, reuse, recycle)
in the triangle, going from the most desirable which is reducing then go to the least desirable which is landfill. Landfill contaminates ground water. Most of our sites came from landfill!! (multiple choice question!!) Most of our super fun cases came from landfills, and one landfill in hazardous waste dump
Chemical oxygen demand (COD)
indirectly measures the amount of organic compounds in water.
Oxygen demand
measure of potential microbial growth.
Wastewater Treatment - Objective (to reduce eutrophication)
o 1. Minimize excess organic material and N+P o 2. Control non-point source pollution o 3. Control algae and aquatic plant life o 4. Wastewater must be treated before discharging into the sea/lake/steam.
HIERARACHY cont.
o 2. Recycling and composting § Recycling - using waste material to produce more of the original product or using waste material in something else · Benefits of recycling o Resource conservation o energy conservation: recycling consumes 50%-90% less energy than manufacturing o pollution abatement: recycling scrap metal as opposed to processing iron ore reduces particulate emissions and mining waste. · Plastic recycling o PET (polyethylene terephthalate) code 1 - recycled into carpets, jackets, film, strapping, new PET bottles. o HDPE (high-density polyethylene) code 2 - recycled into irrigation drainage tiles, sheet plastic, recycling bins. § Composting - is the transformation of organic material (plant matter) through decomposition into soil - like material called compost. · Involves invertebrates (insects and earthworms), and microorganisms. · Composting process o Preparation - shred waste o Digestion - microbes break down waste o Curing - additional curing breaks down solids o Finishing - screen and grind to uniform size.
Example of BOD:
o 80% DO was used up (100%-20%) by bacteria that used both DO, organic matter, and nutrients in the sample water to survive. Therefore, the BOD is HIGH, which means, there is still a HIGH concentration of organic matter in the sample water. o 5% DO was used up (100%-95%) by bacteria that used by DO, organic matter, and nutrients in the sample water to survive. Therefore, the BOD is LOW, which means, there is very little organic matter in the sample water.
Arsenicosis
o Arsenicosis - chronic arsenic poisoning resulting from drinking water with high levels of arsenic over a long period of time. § Limit of 0.01 mg/L of arsenic in drinking water § Effects include: changes in skin color, formation of head patches on skin, skin cancer, lung cancer, cancer of the kidney and bladder, gangrene
BIOCHEMICAL OXYGEN DEMAND (BOD)
o BIOCHEMICAL OXYGEN DEMAND (BOD) - amount of dissolved oxygen needed by aerobic biological organisms to break down organic material § Indirectly measures the concentration of biodegradable organic matter present in a water sample. § When microorganisms reproduce, they use up organic matter + nutrients + dissolved oxygen (DO) The indirect measurement of organic matter is performed by calculating the amount of oxygen used up in a sealed water container.
Blue baby Syndrome (Methemoglobinemia)
o Blue baby Syndrome (Methemoglobinemia) - bluish coloration of the skin due to the presence of deoxygenated hemoglobin in blood vessels near the skin surface. § Nitrate (NO3) - from fertilizers, manure and septic systems contaminate well water · Bacteria can convert nitrate to nitrite, a toxin. o Baby stomach pH is too high to kill bacteria NO3 à NO2 o NO2 binds to hemoglobin, an iron protein. o ◦ Fe2+ → Fe3+ to form methemoglobin o Methemoglobin binds less oxygen and the blood oxygen supply is too low for the brain and infant dies.
cholera
o Cholera (Vibrio cholerae) - Aerobic, gram - negative, motile, curved shape bacterium. § Causative Agent for cholera: acute and diarrheal illness. § Enterotoxin producing bacterium § Annually: 3 - 5 million cases and around 100,000 deaths. § Mostly restricted to the developing world § Large infectious dose: ~108 cells
Coagulation
o Coagulation: after mixing the coagulant chemical, small fine particles in water start to stick to one another. § During coagulation, the coagulant chemicals neutralize the electrical charges of the fine particles in the water, allowing the particles to come closer together and form small clumps. § Coagulant chemicals are added to water before entering the basin. This raw water with the coagulant is mixed rapidly with a flash mixer for even distribution of the chemical. Fast mixing is required (about 60 seconds)
Disinfection
o Disinfection: the goal is to remove or inactivate all disease - causing organisms in water. § Protozoan pathogens are large in size and have been removed with other particles in prior steps. · Bacteria and viruses are now destroyed by addition of a disinfectant such as chlorine. · Disinfection: chlorination, ozonation, and UV radiation.
Dracunculiasis
o Dracunculiasis (Guinea worm disease) § Step 1: human drinks unfiltered water containing copepods with L3 larvae. § Step 2: Larvae are released when copepods die. Larvae penetrate the host's stomach and intestinal wall. They mature and reproduce. § Step 3: Fertilized female worm migrates to surface of skins, causes a blister, and discharged larvae. § Step 4: L1 larvae released into water from the emerging female worm. § Step 5: L1 larvae consumed by a copepod. § Step 6: L1 larvae undergoes two molts in the copepod and becomes a L3 larvae.
E. coli
o E. coli - bacteria endemic in cattle § Possible bloody diarrhea and kidney failure. (may result in hemolytic uremic syndrome (HUS), where the red blood cells are destroyed, and the kidneys fail.) § About 2-7% of infectious lead to this complication. § HUS is the principal cause of acute kidney failure among children in US.
Filtration
o Filtration: the purpose is to remove suspended particles from water by passing the water through a medium such as sand. § As the water goes through the filtration, floc and impurities get stuck in the sand, gravel, and charcoal and the clean water goes through. § The ultimate result is to filter out any particles that remain unsettled during coagulation and sedimentation processes. § MOST PROTOZOA are removed!
Flocculation
o Flocculation: a process of gentle mixing brings the small clumps formed by coagulation into contact with each other, forming floc. · Typically, last 30-45 minutes. The flocculation basin often has a number of compartments with decreasing mixing speeds as the water advances through the basin. This compartmentalized chamber allows increasingly large floc to form without being broken apart by the mixing blades.
Hot Tub Lung
o Hot Tub Lung § Rare infection and allergic reaction of the lungs § Comes from inhaling the bacterium Mycobacterium avium from a hot tub, but not contagious § Bacterial growth is likely to occur in tubs that are not maintained properly. · Chlorine loses most of its disinfectant properties at temperatures above 84F · Bacteria gets into the lungs by bubbles formed in the contaminated water from the hot tub jets. · Bubbles rise to the surface, burst and disperse the bacteria into the air (aerosolization)
Three categories of Solid waste
o Municipal solid waste (MSW) - consists of everyday items that are commonly generated from homes and businesses. § More commonly known as trash or garbage - consists of everyday items we use and then throw away. o Hazardous waste - waste with properties that make it capable of harming human health or the environment o Special waste - a catchall category. Neither municipal solid waste nor a designated hazardous waste. Includes medical waste, construction debris, asbestos, mining waste, agricultural waste.
Know how municipal wastewater is similar to the septic tank system
o Municipal wastewater: you use the facility you wash you do laundry you take a shower you use the toilet facility all of that waste water goes to a septic system where bacteria breaks it down and that is similar to secondary treatment of waste water o and know how that is similar to leachate how that further kind of filters the waste water similar analogous different but similar to what we do in a larger scale in Orange County, where we get our source of water depending upon where we live. § We generate waste water it goes to a larger waste treatment plant, it in central orange country where its recycled into reclaimed water in pink lavender colored pipes and then it gets sent up to the Santa Ana river to the rechanged basin pods and filters down to further cleansing for people to drink in 20 years. And how is similar to a septic system is that it generates a waste that goes into a tank, the bacteria biological processes breaks it down and then that water comes out of the tank and goes into the leachate where it percolates the soil and the soil also has bacteria but its also another filter process.
AB1826
o Organics recycling requirements depend on the amount o organic waste generated by the business each week. The minimum threshold of organic waste generation by business decreases over time, so a larger proportion of the commercial sector will be required to comply in the new organics recycling requirements in the coming years. The mandatory commercial organics recycling law (AB 1826) was signed in 2014 to help achieve California's aggressive recycling and greenhouse gas emission goals. California landfills about 30 million tons of waste each year, of which more than 30% is organic, which could be composted or used to produce renewable energy. Greenhouse gas emissions contributing to global climate change
What is in wastewater? Mostly water
o Organisms (bacteria, protozoa, worms, and viruses), Organic matter (carbon-based chemicals that are the building blocks of most living things.), Oil/grease, inorganics (sodium, potassium, calcium), nutrients (nitrates and phosphates), solids (organic/inorganic)
Parasitic Protozoa (Cryptosporidium parvum
o Parasitic Protozoa (Cryptosporidium parvum) § Causes gastrointestinal illness cryptosporidiosis § Forms an oocyst that is resistant to disinfection § Symptoms: watery diarrhea, cramps, nausea, fever § Transmittance by ingestion of water with fecal contamination (fecal-oral route)
Recycled water Treatment
o Recycled water can be used to irrigate golf courses and landscapes. If done properly, it can be cleaner or just as clean as bottled water.
Sedimentation
o Sedimentation: decreases the concentration of suspended particles in the water, which reduces the load on the filters. § Water is allowed to sit in a rank for a pre-designed number of hours allowing flocs and other heavy materials to settle at the bottom of the tank. § At this stage in the treatment process should remove 90% of the suspended particles from the water, including bacteria.
Sludge: Anaerobic Digester
o Sludge from primary and secondary clarifiers, aeration basin, and trickling filters are sent to anaerobic digester for further decomposition. o Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. § Produce methane gas § Produce biosolids (can be used as fertilizers) o Anaerobic digestion is widely used as a renewable energy source because the process produces a methane.
Wastewater Treatment Process!! (stage 1)
o Stage 1: Preliminary and Primary Treatment - removes approximately 50 - 65% of suspended solids through screening and sedimentation. § Preliminary treatment: screens and grit chamber remove large debris. · Preliminary Treatment: Bar Screen and Grit Chamber o Bar screen removes large debris § BAR SCREEN - catches larger objects that have gotten into sewer system such as bricks, bottles, pieces of wood. o Grit chamber removes smaller inorganic material like pebbles and sand that can damage equipment. § Primary treatment: Sedimentation tank (primary clarifier) removes smaller solids. · Primary treatment: Sedimentation o Removes more grit, solids that settle down. o Floating waste (oil and fat) are skimmed from the surface. o Scum and sludge are sent to anaerobic digester. o Sedimentation Basin: Rectangular Basin and Clarifier
Wastewater Treatment Process!! (stage 2)
o Stage 2: Secondary Treatment - removes about 90 - 95% of the dissolved pollutants (organic matter) which is accomplished by aeration basin/activated slugged or trickling filter. § Biological process digest organic wastes § Secondary Treatment #1: Aeration Basin/activated sludge · Oxygen - rich aeration tanks, microbes (bacteria and protozoa) living in the wastewater consume most of the organic material. · Oxygen + organic matter (food) = many microbes. · The microbes and remaining solids are separated from the treated water in the secondary clarifier · Does not remove viruses or heavy metals. § Secondary Treatment #2: Trickling Filters · Trickling filters - beds of plastics filter media covered with microbial slime absorb organic material as wastewater is sprayed over the surface.
Wastewater Treatment Process!! (stage 3)
o Stage 3: Tertiary Treatment - remove remaining pollutants (optional) § DISINFECTION (REQUIRED) - usually chlorination § Disinfection with chlorine or other disinfectants such as ozone or UV (REQUIRED) · Since chlorine is toxic to marine organisms, chlorine is removed before discharge into the ocean, rives, and other environments. § Combination of several biological, chemical, or physical processes designed to remove such pollutants, phosphates, nitrates, ammonia, and organic chemicals (OPTIONAL) § Reduces the concentration of remaining nutrients to about 1% of that present in raw sewage.
Groundwater Recharge System (GWRS) or Groundwater Replenishment System
o Step 1: Microfiltration (MF) § MF uses straws with tiny holes in the sides that are up to 300 times smaller than a human hair. § MF filters out particles, protozoa, and bacteria, also other viruses attached. o Step 2: Reverse Osmosis o Step 3: UV with Hydrogen Peroxide § UV with hydrogen peroxide provides an additional safety barrier that disinfects and destroys trace compounds that may have passed through RO membranes.
Groundwater Recharge System (GWRS) or Groundwater Replenishment System
o The GWRS purification process begins at the Orange County Sanitation District (OCSD) : which sewer water is treated to remove nutrients and contaminants (enough to discharge the ocean) o Instead of discharging the water, up to one-third (1/3) of the treated water is purified even further by OCWD. o This purified water is used as a barrier for seawater intrusion and to recharge GW via the Anaheim and other percolation basins.
PAYT PROGRAM
o User fee based on the amount of waste discarded. EPA reports an average of 25%-45% drop in amounts of waste and about 32%-59% in recycling
the difference between dump and sanitary landfill
o sanitary landfill has a liner. Put a compound clay down which forms a nice bathtub so water does not go through, and then put a liner and then the channels which is called a leachate collection system. o And the second thing about landfill is landfill gas collection system. o Need to know where to build sanitary landfill!! Its on the slide. Where to build the liner significantly above the saturated zone or groundwater because you do not want it close because it can get contaminated and you want it away from residents but does not happen in California because property is too valuable, so you want to build this line system and then you collect the leachate, the water that goes through the trash, you build a series of wells around the perimeter landfill and in through the landfill. And then they collect that gas and burn it, which makes electricity. They cover the trash every day and do not set it on fire. That's the difference between sanitary landfill and a dump.
Dissolved oxygen (DO)
required for robust aquatic life.
First flush
the first rainstorm (winter-spring) following many months of dry weather that flushes out debris which has accumulated inside the storm drain system. This accumulation is the combined effects of littering, illegal dumping, windblown trash and other toxic liquids and chemicals.
why do we pipe for Canal water from Northern California to Southern California what is a reason that it that's an advantage that we canal water from Northern California to Southern California:
we get more rainfall.
Nitrate and phosphate
when they enter in the algae blooms and the algae uses up the dissolved oxygen when it dissolves oxygen depletes and algae dies and falls to the bottom of the pond and then you got break down bacteria decomposer and algae blocks the sunlight and what happens when all the dissolved oxygen is gone in a body of water - hypoxic and fish kill.
Disadvantages for Chlorine Treatment
§ Chlorine addition creates disinfection-by-product § When the chlorine reacts with organic material disinfection-by-products are potentially formed. Example: Trihalomethanes § Provides poor cryptosporidium and Giardia control § More space required.
Advantages for Chlorine Treatment
§ Provides a strong residual chlorine in distribution system. · Residual chlorine is the available free chlorine to protect water during distribution. · Provides a barrier of protection throughout the system when adequate chlorine residual is maintained. § Easy to apply and inexpensive § Effective at Low concentrations § Reduces nuisance odor from hydrogen sulfide.
STAGES OF EUTROPHICATION
§ Stage 1: Nutrients enter water - nitrates and/or phosphates § Stage 2: plants and microorganisms thrive § Stage 3: Algal "bloom" - algae, plankton, cyanobacteria grow rapidly near the surface of the water system. § Stage 4: Decomposition occurs - algae die and settle to the bottom · Dead algae are decomposed by aerobic bacteria, depleting dissolved oxygen in the water system. · Aerobic bacteria use DO to live · Certain anaerobic bacteria can also release toxic chemicals (hydrogen sulfide) § Stage 5: formation of hypoxic zones - decomposition depletes oxygen and deprives the deeper waters of oxygen which can kill fish, shellfish and other aquatic life.
Artesian Water or Artesian Well
Ø Artesian Water or Artesian Well: the name of water from a well tapping a confined aquifer in which the water level stands at some height above the top of the aquifer.
Chlorination
Ø Chlorination: most frequent form of disinfection. § Can be applied for the deactivation of most microorganisms and is cheap. § Hypochlorous acid (HOCL), most effective chlorine chemical to kill microbes. § Four forms of chlorine that can produce HOCL in water: chlorine gas, hypochlorite (bleach), chloramines, chlorine dioxide (most dangerous)
Know the basic requirements for a healthy environment, which are associated with healthy communities.
Ø Clean Air o Air pollution - major environment risk, estimate 2 million premature deaths worldwide o 8th most important risk factor and responsible for 2.7% of global burden of disease. Ø Safe and sufficient water o 2.3 billion people have gained access to improved drinking water between 1990-2012. o 1.5 million deaths in 1990 and now 600,000 in 2012. Ø Adequate and safe food o 1 billion hungry people in the world.
Disinfection By-products (DBPs)
Ø Disinfection By-products (DBPs) o Chlorination of water leads to the formation of small amounts of disinfection-by-products. The free chlorine reacts with organic contaminants, for example methane to form trihalomethane. o DBPs are carcinogens and reproductive toxins (lower birthweight) o Disinfection is PARAMOUNT in the control of bacteria in water o Represent a small hazard!
Eutrophication
Ø Eutrophication: is the enrichment of an ecosystem with chemical nutrients, compounds containing nitrogen, phosphorus, or both, in the form of nitrate and phosphates. o THE AGING PROCESS OF A BODY OF WATER o The increase in available nutrients promotes an algal bloom § In aquatic environments, enhanced growth of algae (phytoplankton, cyanobacteria) disrupts normal functioning of the ecosystem, causing a variety of problems, including hypoxia (aka: dead zone) o The eutrophication process and subsequent formation of sea-bottom hypoxia in the Gulf of Mexico
Know how bottled water regulations differ from tap water regulations.
Ø Natural Resources Defense Council examined 103 brands of bottled water o 1/3 contained a chemical of bacterial contaminant that exceeded industry standards or government regulations for drinking water from the tap. o EPA regulates drinking water from the tap o FDA regulates bottled water o The Natural Resources Defense Council report concluded that "Therefore, while much tap water is indeed risky, having compared available data, we conclude that there is no assurance that bottled water is any safer than tap water. o The federal regulations that govern bottled water only apply if it is transported across state lines, and then only require it to be "as good as" tap water.
Ozonation
Ø Ozonation o Has many advantages as a disinfectant § Disinfection with ozone occurs 30,000 times faster than with chlorine and is much more potent than chlorine. § Does not add chemicals to water § No DBPs formed in the system § Kills protozoa such as Giardia and Cryptosporidia.
Percolation
Ø Percolation o Groundwater does not typically require coagulation, sedimentation, filtration steps of the surface drinking water treatment because groundwater has been purified by natural filtration system (through the percolation process)
Salt Water Barriers
Ø Salt Water Barriers o Purified water is used as a barrier for seawater intrusion (aka: salt water)
Spring Water
Ø Spring Water: the name of water derived from an underground formation from which water flows naturally to the surface of the earth.
Might have a short question about pollution
Ø This water body is polluted what do we expect it about the BOD to be, the appearance to be, how would you investigate in this. What would you do as an environmental health practitioner to help try to control this nitrate and phosphate, or this waste water source from entering the body causing hypoxic zone. Got a called about dead fish in the river, where would you start? Can start with BOD test, look for sources of contamination, try to identify what cause the fish to dead and where are the fish healthy and if you think about the slide about the industry discharged pipe or a waste water pipe pumping into the river and you got hypoxic zone and kill fish and you got the recovery zone, and everything is healthy.
Know different types of freshwater resources and availability (groundwater, lakes, etc.) Know important facts about water use (globally, in US, and in OC). Know the different sources of OC freshwater.
Ø Types of freshwater resources o Global water (ocean), freshwater (groundwater, glaciers, and ice caps), surface water and other freshwater (lakes, ice, and snow) Ø Surface water: all water naturally open to the atmosphere. Ø Groundwater: the supply of freshwater found beneath the Earth's surface, usually in aquifers, which supplies wells and springs. Ø Water use (1st ,2nd, and last) o World (agriculture, industry, domestic) o North America (Industry, agriculture, domestic) o Orange County (Landscaping 58%) Ø Different sources of OC freshwater o Domestic: Groundwater, Santa Ana River o Imported: State Water Project, Colorado River Aqueduct Ø OC, about 60-70% of the local water comes from groundwater and the rest is imported from SWP and CRA.
UV
Ø UV o UV light can damage the DNA of microbes and cause instantaneous microbe inactivation § Advantage · No disinfection - by - product · No chemicals · Low maintenance § Disadvantages · No residual disinfectant · Pretreatment may be necessary for raw water with moderate mineral content · Anything with blocks UV light from reaching the water will result in a lack of treatment, so water must be free of turbidity.