FACTSHEET TASTE AND ODOR

Environmental Contaminant Treatment

Taste and Odor -Causing Compounds in Drinking Water

The primary sources of taste and odor problems common name “blue-green algae” has remained. Man-Made Chemicals in drinking water are algae and bacteria. However, Cyanobacteria are photosynthetic bacteria. In Man-made chemicals are another source of other anthropogenic sources such as wastewater addition to the blue-green color of many inferred taste and odor-causing chemicals in drinking discharges and chemical spills also act as sources by the name, other species can be red, brown, or water. For example, methyl tertiary butyl ether of chemicals that cause off tastes and odors. yellow. Cyanobacteria are most commonly found (MTBE), a gasoline additive persistent in Such chemicals can affect both groundwater and in eutrophic waters (waters with high levels of groundwater and recreational surface waters, surface water. nutrients) and shallow reservoirs, and can occur has an odor threshold as low as 5 parts per as surface scum, benthic (bottom) mats, and on billion. Dissolved in water, it smells oily and like TYPES OF TASTE AND aquatic weeds (Hoehn, 2002). In the 1960’s turpentine. Industrial phenols can create odor and 1970’s, it was discovered that cyanobacteria problems. Hydrocarbons and volatile organic ODOR PROBLEMS produce geosmin and MIB as intracellular by- compounds such as fuels and solvents produce

products. As a bloom progresses, bacteria die, oily, paint-like, and medicinal odors. There are four basic taste types: sour, sweet, salty releasing these odorous chemicals into the water. and bitter. There are also a variety of odor types including earthy, musty, chemical, and chlorinous. ALGAE AND BACTERIA Actinomycetes The table on the reverse side lists several taste Actinomycetes are spore-forming bacteria that BLOOM PATTERNS and odor types and their potential causes. grow as branching filaments in water. Closely A bloom occurs in a surface water body when related to cyanobacteria, they have simple cells. light, temperature, and nutrient conditions are THE CAUSES OF TASTE AND Actinomycetes also live in soil. In fact, it is the favorable for one type of algae or bacteria over geosmin-producing soil variety that causes soil to ODOR PROBLEMS another. This combination allows one organism to smell “earthy.” Other species produce antibiotics. become dominant. It is an ecological imbalance Some species of algae and bacteria naturally Aquatic actinomycetes grow in aerobic mud, on often triggered by pollution. Nitrates, organic produce odorous chemicals inside their cells. decaying vegetation, and in the excrement phosphorus and ammonia are discharged into the Geosmin (trans-1, 10-dimethyl-trans-9-decalol) of zebra mussels. The bacteria help to degrade water body from water treatment plants or are and MIB (2-methylisoborneol) are common cellulose and other plant parts, and for this carried in by watershed runoff (including runoff odorous chemicals. The earthy and musty odors reason thrive as a result of an algae bloom from pig and cattle feed lots and fertilizer from generated by geosmin and MIB are detectable by (Hoehn, 2002). Actinomycetes, like cyanobacteria, agricultural fields). The conditions favorable to many people at concentrations of 5 to 10 parts produce geosmin and MIB. blooms are seasonal. Spring and winter conditions per trillion. When large numbers of algae and favor golden brown algae and fishy, cucumber bacteria flourish in a water body (an “algae bloom”), Other Algal and Natural Sources odors. Summer and fall conditions favor geosmin taste and odor-compound concentrations increase Green algae blooms in a reservoir can produce and MIB-producing bacteria and earthy and musty to levels above this threshold and cause taste a grassy or fishy odor. Golden-brown algae, odors. Generally, the most common bloom month and odor problems. particularly the species Synura, can produce a is September. cucumber, melon, or fishy odor. Biological activity Cyanobacteria (Blue-Green Algae) in surface waters can produce 2,4-heptadienal Cyanobacteria are known by several names, and decadienal, which have a fishy, rancid odor. MEASUREMENT AND including “blue-green algae”, “blue greens”, In addition, dissolved metals such as zinc, REGULATION OF TASTE AND and “cyanophyta”. To the biologist, they are not manganese, copper, and iron can produce a ODOR QUALITY technically algae (a multi-celled plant), but metallic taste. bacteria. This was not known until the advent There are several methods of taste and odor of high-powered microscopes, however, the quality measurement and very few regulations. TASTE OR ODOR SOURCE

FACTSHEET Earthy Geosmin Musty MIB, isopropylmethoxypyrazine (IPMP), isobutylmethoxypyrazine (IBMP) Turpentine, oily Methyl tertiary butyl ether (MTBE) Fishy/rancid 2,4-Heptadienal, decandienal, octanal The most frequently used measuring system is Chlorinous Chlorine the Total Odor Number (TON), a method based Medicinal Chlorophenols, iodoform on the persistence of an odor after dilution. Oily, gas-like, paint Hydrocarbons, volatile organic compounds (VOCs) Other methods include Flavor Profile Analysis Metallic Iron, copper, zinc, manganese and analytical measurement of chemical Grassy Green algae concentrations. Regulatory limits are few. The United States Environmental Protection Agency (USEPA) has issued a secondary maximum concentration limit (MCL) limiting the TON to 3. larger utilities. Chlorine is widely used for the For over 30 years, Trojan has specialized in UV Iron, manganese, copper, and zinc have USEPA oxidation of taste and odor-causing chemicals, applications for water treatment and wastewater MCLs ranging from 0.5 to 5 parts per million. but itself can produce chlorinous odors and disinfection. Over 6,500 Trojan UV systems are However, the primary regulator with respect to disinfection by-products such as THMs and HAAs. treating municipal wastewater in more than 80 taste and odor is the consumer. Ozonation is also used, but is expensive, complex countries around the world. Tens of thousands to operate, and can form bromate, a harmful by- of industrial and residential Trojan UV treatment ALGAL TOXINS product. However, UV-photolysis and UV-oxidation systems are in operation in industries and using UV light and hydrogen peroxide is a cost- households worldwide. Now, Trojan offers the In addition to producing chemicals that impact effective alternative for treating a wide variety of industry standard in Environmental Contaminant the aesthetic quality of water, certain species taste and odor problems. MIB, geosmin, MTBE, Treatment (ECT). Trojan’s UV-photolysis and UV- of cyanobacteria produce toxins (“cyanotoxins”) phenols, VOCs, and many others contaminants oxidation systems are capable of cost-effectively that can cause harm to animals and humans. can be treated with UV-oxidation. This technology removing environmental contaminants from a Toxic cyanobacteria are indistinguishable from requires the photolysis of hydrogen peroxide variety of water streams. With its optimized non-toxic cyanobacteria under a microscope and with UV light to generate hydroxyl radicals. The technology, Trojan is the leader in ECT, offering both types may be present in a bloom. Multiple hydroxyl radical is one of the most powerful the most cost effective, highest quality UV classes of cyanotoxins exist, including microcystin, oxidizing agents known and reacts rapidly with solutions available. cylindrospermopsin, and anatoxin-a. Cyanotoxins organic constituents in the water, including taste can be present wherever blooms occur and as a and odor compounds, breaking them down into result, several regulating agencies worldwide have their elemental, non-odorous components. Trojan’s issued guidance regulations. Research in the U.S. UV-oxidation reactors provide a reliable barrier and Canada has shown that a high percentage of to taste and odor compounds and do not form raw water taken from water supplies undergoing bromate. In addition, the same UV system used a cyanobacteria bloom contained cyanotoxins, for taste and odor control simultaneously performs in addition to other taste and odor-causing disinfection. This reduces or eliminates the source chemicals (Carmichael, 2001). In the U.S., the of unpleasant chlorinous odors resulting from the USEPA has listed freshwater cyanobacteria and use of chlorine as a primary disinfectant. their toxins on the Contaminant Candidate List. In addition, New Zealand, Germany, and the World TREATING MULTIPLE Health Organization (WHO) have established CONTAMINANTS WITH ONE microcystin guidelines of 1.0 ppb, while Canada Cyanobacteria Bloom in Lake Manatee, Florida has established a 1.5 ppb guideline. UV SYSTEM (Photo courtesy of Bruce MacLeod) As a further benefit to taste and odor control and TREATMENT ALTERNATIVES – microbial disinfection, the Trojan UV system will References: UV LIGHT A KEY disinfect Cryptosporidium and Giardia. The process Hoehn, R.C. 2002. Odor Production by Algae. Conference will also treat many other dissolved organic Workshop Presentation: Understanding and Controlling Many utilities use powdered activated carbon compounds present in the water, including the Taste and Odor of Drinking Water. AWWA Annual (PAC) to treat taste and odor problems. However, endocrine disruptors, N-nitrosodimethylamine Conference, New Orleans. June 16, 2002. Carmichael, W. W. 2001. Assessment of Blue-Green large doses of PAC are required to treat geosmin (NDMA), pesticides, and algal toxins. Algal Toxins in Raw and Finished Drinking Water. AWWA and MIB, making it impractical, especially for Research Foundation, Denver. 179 pgs.

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