Taming taste and odor (T & O) problems in a water treatment plant

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Courtesy of Jenfitch, LLC

Taming Taste & Odor (T&O) Problems

Some taste and odors are caused by mineral constituents in the water, e.g. excess chlorine and hydrogen sulfide. However the majority of taste and odor are the result of biologic activity. Spring turnover of lakes and algal blooms are responsible for Blue-green algae (Cyanobacterium), Green algae and diatoms that introduce filter clogging organisms that also foul anion exchange resins, degrade effluent quality of demineralized water, which also interfere with flocculation and sedimentation and produce toxic organic compounds (negatively charged colloid oils) that contribute to taste and odor in the finished water.

People involved in water treatment speak generally of an 'algae' problem. In fact, it is more accurate to use the term 'plankton'. This term includes all the micro-algae that under favorable conditions (the presence of ideal amounts of nutrients, heat, and sunlight in the environment) can undergo periods of explosive growth. It also includes animal plankton (zooplankton), which belong to a higher level in the food chain, as well as Actinomycetes. All these organisms are sized within a range of a few microns to a few millimeters.

 Examples of organism derived odors are:

Species

Moderate

Abundant

Cyanophyceae (Blue Green)

 

 

Anabaena

Grassy

Septic

Aphanizomenon

Grassy

Septic

Microcytis

Grassy

Septic

Oscillatoria sp (filamentous)

Grassy

Musty

Chorophyceae (Green)

 

 

Chlamydomonas

Fishy

Fishy

Chlorella

Fishy

Fishy

Pandorina

Fishy

Fishy

Pediastrum

Fishy

Fishy

Scenedesmus

Fishy

Fishy

Staurastrum

Fishy

Fishy

Volvox

Fishy

Fishy

Chrysophyceae (brown)

 

 

Dinobryon

Violet

Fishy

Synura

Cucumber

Fishy

Bacillariophyceae (diatoms)

 

 

Asterionella

Geranium

Fishy

Cyclolella

Geranium

Fishy

Melosira

Geranium

Musty

Stephanodiscus

Geranium

Fishy

Synedra

Geranium

Musty

Tabellaria

Geranium

Fishy

Euglenophyceae (Flagellates)

 

 

Euglena

Musty

Musty

Actinobacteria

 

 

Streptomyces

Earthy

Musty

Chlorophyll a is a photosynthetic pigment that serves as a measurable parameter for all algae production. Quantitative biomass estimates can be made noting that on average 1.5% of algal organic matter is chlorophyll a. Qualitative assessment of primary production on water quality can be based on chlorophyll a concentrations as noted below.

 

Chlr-a Concentration (g/l)

Water discoloration

<10

No discoloration

10-15

Some discoloration, some algal scum

20-30

Deep discoloration, algal scum

>30

Very deep discoloration, algal matting

 

Algae Elimination

When practical and cost effective, mechanical means of removing algae is a first choice. It effectively removes particulates that would significantly contribute to organic loading and removes particulates that would increase disinfection by products for a water source.

When choosing a chemical disinfectant, it is helpful to know and plan accordingly to the chemistry oxidation potential and the oxidation energy it provides. When isolating specific compounds, e.g. peroxide, some portion of the peroxide becomes water and back to peroxide. Though the percent of peroxide to water appears stable, on a molecular level there is continuous movement back and forth and it is this constant movement of electrons that gives a measurable voltage. In this peroxide example, the reaction favors the peroxide side of the equation, hence gives a positive voltage. If the reaction favored production of water, the voltage reading would be negative. Therefore, a compounds relative ability to give up electrons is represented by a positive voltage.

Chemical

Reaction

Volts at 25 deg C

Ozone

O3 + 2H+ + 2e O2 + H2O

2.87

JC 9450

Mixed oxygen radicals

Not determined

Peroxide (acid)

H2O2 + 2H+ + 2e 2H2O

1.76

Permanganate

MnO4 + 8H+ + 5e Mn2+ + 4H2O

1.46

Hypochlorite (acid)

HOCl + H+ + 2e Cl- +  H2O

1.49

Chlorine

Cl2 + 2e 2Cl-

1.39

Chlorine Dioxide

ClO2 (gas) + e ClO2-

1.15

Bromine

Br2 + 2e 2Br-

1.07

Hypochlorite (basic)

OCl- + H2O + 2e Cl- + 20H-

0.90

Peroxide (basic)

H2O2 + 2e 2OH-

0.87

Oxygen

O2 + 2H2O + 4e 40H-

0.40

 

 

 

A comparison of available data of strong oxidants applied to algae is:

Oxidant

Dosage mg/l

Reaction time, min

% deactivation

Permanganate

1

30

9.5

Permanganate

2

30

68

Permanganate

3

30

89

Permanganate

1

60

68

Permanganate

2

60

98

Permanganate

3

60

100

Peroxide

100

30

50

Peroxide

100

60

75

Ozone

1

1

14

Ozone

2

1

64

Ozone

3

1

70

Ozone

1

5

26

Ozone

2

5

72

Ozone

3

5

76

JC 9450

ORP > 400

Insufficient data

100

 

Green algae and most diatoms, along with the excreted organics that cause odors are susceptible to conventional water treatment chemistry. But, Blue-green and protozoas require the more aggressive oxygen radicals to be deactivated as well as the organics released that cause odors. Especially when phytoplankton are senescent (the growth phase following maturity and prior to death, characterized by accumulated metabolic products, increased respiration, and loss of dry weight) and decaying.  

Blue-green algae (also known as cyanobacteria) are microscopic organisms found naturally in surface water. True algae and blue-green algae both utilize some form of chlorophyll to perform photosynthesis. True algae are essentially plants. Blue-green algae are actually bacteria that exhibit a blue or green color, similar to true algae, but contain cellular structures typical of bacterial cells. True algae and blue-green algae are very different organisms and therefore should not be treated the same. There are no known harmful toxins released by dying true algae. Blue-green algae, however, can contain harmful toxins within the cell wall which may be released during cell growth or death.

Toxins of critical concern:

Cyanophyceae (Blue Green)

 

Anatoxin-a

neurotoxic

Cylindrospermopsin

Hepatotoxic

Microcystin

Hepatotoxic

Saxitoxin

Neurotoxic

Actinobacteria

 

Geosmin (Geo)

Muddy smell

Methylisoborneol (MIB)

Musty smell

 

The choice of oxidizer must also consider the oxidizer impact on the toxins secreted by marine organisms. Data summarizing this impact is:

 

Anatoxin-a

Cylindrospermopsin

Microcystin

Saxitoxin

Geo/MIB5

Chlorine1

Not effective

Effective (at low pH)

Effective

Not effective

Not effective

Chloramine2

Not effective

Not effective

Not effective

Not effective

Not effective

Chlorine Dioxide2

Not effective

Not effective

Not effective

Not effective

Not effective

Permanganate

Effective

Not effective

Effective

Not effective

Not effective

Ozone3

Effective

Effective

Effective

Not effective

Not effective

UV/peroxide

Effective

Effective

Not effective

Not effective

Effective

JC 94504

Effective

Effective

Effective

Effective

Effective

1.       Reactivity of chlorine with toxins is influenced by pH of the water and the loading of organic matter

2.       Very high doses and long contact times can effect these toxins but will create compliance issues with residual concentrations of chlorite and chlorate

3.       Ozone reacts quickly with all toxins but is not capable of providing a contact time needed to be effective against Saxitoxin and Geosmin/MIB, which require CT much in excess of 20 min.

4.       Based on available data on the effectiveness of the joint action of multiple oxygen radicals catalyzed by Haber-Weiss and Fenton reagents.

5.       Geo/MIB are susceptible to oxidation by hydroxyl radicals generated by the combination of peroxide and UV radiation of appropriate wavelength or by oxygen radicals catalyzed by “Fenton” reactions provide by JC 9450.

Invertebrates comensal with algae

As sediment builds with any body of water, benthic organisms associated with algal growth are:

A.      Amphipods:  A small crustacean with laterally compressed bodies that range in size from 1-340 millimetres (mm) and are mostly detrivores and scavengers. There are 1900 known freshwater species.

B.      Copepods: Meaning “oar feet”, are small crustaceans 1-2 mm in size with a tear drop shape and large antennae, most  are “planktonic” (drift with water current), some other are “benthic” (live in muds).

C.      Isopods: Small crustaceans that are typically flattened dorsoventrally. Approximately 500 species live in freshwater and are mainly scavengers, some are predators and others are ectoparasites of fish.

D.      Ostracods: A diverse small crustacean generally 1-30 mm in size. Their bodies are flattened and protected by a bivalve like calcareous shell. This group includes carnivores, herbivores, scavengers and filter feeders.

E.       Nematodes: Round worms with a tubular digestive system and are parasitic.

F.       Water Mites/water fleas: Though are normally benthic, they are good swimmers and are carnivorous and parasitic

G.     Insect larvae

Though most invertebrates are captured in filter systems or die as a result of exposure to chemical treatments, some survive to reproduce in the system to have their larvae enter the distribution system. These invertebrates may harbor and protect bacteria from disinfection with chlorine and monochloramines at concentrations normally present in distribution systems. Associated bacteria, either enteric or colonizing the exoskeleton, may survive though the invertebrate is inactivated. Invertebrates may therefore:

1.       Constitute a health hazard if they are carrying or become exposed to and associated with bacterial pathogens.

2.       Contribute significantly to the organic load entering the distribution system.

3.       Contribute to the continued colonization of distribution systems by invertebrate associated bacteria in spite of residual chlorine.

4.       Decrease the effectiveness of chlorination by increasing the chlorine demand of the water.

5.       Contribute to the cause of taste and odors, water discoloration, water meter clogging and high turbidity.

Chemical control of invertebrates

a.       Insect larvae: Chlorination as high as 50mg/l with CT of 24 hours has been shown to be ineffective against insect larvae. Copper sulfate is also ineffective.

b.      Copepods: Chloramine is preferred over free chlorine.

c.       Amphipods:  Amphipods will survive in distribution systems by living off rust and are cannibalistic to dead amphipods. Laboratory observations revealed a 58% survival rate with a chlorine residual of 1 mg/l. They are resistant to normal chlorine residuals and will live for up to a year. Survivability was slightly decreased with a chloramines residual.

d.      Water fleas and Water mites are more sensitive to chlorine residual than chloramine levels greater than 0.22mg/l with a CT of less than 10 hrs

e.      Nematodes: Nematodes are 3 to 4 times orders of magnitude more resistant to free chlorine than bacteria and exhibit CT coefficients of between 450 to 2550 mg*min/l

f.        JC 9450: The aquarium industry has written extensively on the importance of ORP control and reports that an ORP above 400 will kill all invertebrates. Necropsies of chickens has revealed thatJC 9450, as a water treatment (ORP of 550), desiccates intestinal nematodes.

Bacteria associated with Invertebrates

Bacteria are associated with invertebrates and are either enteric or may colonize their exoskeleton. Most common pathogens associated with invertebrates are:

Bacteria

Associated diseases

Acinetobacter sp

Perodontitis, blood infections, urinary tract infections, pneumonia, bacteremia, meningitis

Achromobacter xylooxidans

Bacteremia

Aeromonas hydrophila

Dysenteric gastroenteritis, cholera, myonecrosis, eczema, cellulitis

Bacillus sp

Gastroenteritis

Chromobacter violaceum

Skin lesions, sepsis, liver abscesses

Enterobactor sp

Urinary infections, respiratory infections

Flavobacterium meningosepticum

Meningitis, endocarditis, bacteremia, necrotizing fasciitis, sepsis

Klebsiella sp.

Pneumonia, urinary infections, septicemia, meningitis, diarrhea

Moraxella sp.

Respiratory infections, pneumonia, conjunctivitis

Pasteurella sp

Sepsis, respiratory infections, cellulitis, arthritis

Pseudomonas sp

Nosocomial infections

Salmonella sp.

Gastroenteritis, typhoid fever, blood stream infections

Serratia sp

Infections of blood, respiratory system and urinary tract, meningitis, arthritis, endocarditis, osteomyelitis

Staphylococcus sp

Gastroenteritis

 

Control of invertebrate associated bacteria

Bacteria associated with invertebrates always survive better than similarly unassociated bacteria.  Free available chlorine (FAC) at equivalent contact times and concentrations is mostly more effective in inactivating associated bacteria than monochloramine, regardless of temperature. Enterobacterand Salmonellabehaved similarly in the presence of FAC at all concentrations and temperatures, while Klebsiellawas mostly susceptible to inactivation with FAC at both 40 C and 200 C.Enterobacterwas more resistant to inactivation with monochloramines than the other bacteria at all concentrations and temperatures.Enterobacter, after disinfection with monochloramines for 2 hours, that which survived either decreased slightly or increased activity.

Tests revealed that bacteria are able to escape inactivation by either FAC or monochloramines, and survive better than the same bacteria unassociated in the water column. Bacteria associated with particulate granular activated carbon were afforded enhanced protection from inactivation with FAC and monochloramines when compared to unassociated bacteria under similar conditions. Therefore, the association of bacteria with invertebrates affords protection to recently attached bacteria as well as to their natural flora.

The failure of conventional approaches to inactivate invertebrates and associated bacteria points to the need to apply advanced oxidation technology. As an alternative to the impact of mg/l of a chemical agent, the ability of a chemical agent to impart significant ORP energy is a viable alternative. Research has revealed that an ORP of greater than 400 is very effective in inactivating both invertebrates and associated bacteria. JC 9450effectively enables application of ORP energy with far less concentrations than conventional oxidizer applications.

JC 9450: ORP Control by generating Oxygen Species in Water.

Aquaculture and aquarium science has determined that an ORP above +400 mV is sufficient oxidation energy to deactivate invertebrates, algae, comensal bacteria and detoxify algae related toxins. To reach ORP +400 mV with ozone, small batches of water must be treated with CT of 20 minutes or more. Conventional chlorine derivatives, to reach ORP +400 mV will result in compliance issues with excess chlorites and chlorates. With peroxide/UV protocols, there is the expense of UV equipment, then the calculations of peroxide to kilowatt-hrs relative to the organic load to be deactivated.JC 9450is a high energy (derived from oxygen radicals) liquid that is easily injected and gives ORP control without risk of compliance issues.

Active oxygen species are very good oxidizers and are generated in water environments. The decomposition of water, and oxo-compounds, generate several oxygen products. These oxygen products are various oxidation states of oxygen called: superoxide [O2-], hydroxyl [OH-], nascent oxygen [1O2], hydroperoxyl [HO2-], and peroxide [O22-].

 

Description: SEVENenvirotox

 

These oxygen radicals play a double role of both oxidant and antioxidant. As oxidant, oxygen species exert harmful effects on living water organisms. Oxygen species also are very important antioxidants transferring pollutants present in lakes and rivers into nontoxic products by their oxidative degradation, usually in the free radical and singlet oxygen way.  The hydroxyl radical has a very high oxidation potential (2.8V), compared to singlet oxygen (2.7V).  Additionally, hydroxyl and singlet radicals show very high values of second order rate constants for organic compounds. This means after an oxygen radical initially reacts with organic material, substantial energy is available to continue breaking down the organic compound, i.e the oxygen radical is not limited to reacting with organic material just once. Also, withJC 9450,oxygen radicals are generated during the combination with the metal/mineral constituents ofJC 9450. These reactions are referred to as “Haber-Weiss” and “Fenton” reactions.

1.    Me[n+1]+ + O2- ------2H+---à Men+ + H2O2

2.    H2O2 + Men+ ----à HO. + HO- + Me[n+1]+

It is this property of JC 9450that enables reliable and effective ORP measurement, catalyzed oxygen reactions with organics,

Description: TWELVEenvirotox

 

improved second order rate reactions, and low concentrations of chemistry vs mg/l concerns with conventional treatment protocols and makesJC 9450effective as:

·         Disinfectant; kills bacteria and viruses

·         Oxidation of organics

·         Oxidations of inorganics

·         Color removal

·         Odor removal; sulfur and organic odors

·         Algae control

·         Micro coagulation aiding filtration

·         BOD/COD reduction

·         VOC elimination

 

Bibliography

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  2. Ebbing D.D.: General Chemistry 4th edition, Houghton Mifflin Co., 1993.
  3. Manhan S.E.: Environmental Chemistry 6th edition, Lewis Publishers 1994.
  4. Loudon G.M.: Organic Chemistry 2nd Edition, Benjamin-Cummings Pubishing Co., 1988.
  5. Stryer L.: Biochemistry, W.H. Freeman & Co.,1975.
  6. Cotton F.A.: Advanced Inorganic Chemistry 6th edition,John Wiley & Sons Inc., 1999.
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  8. Kruk I.: Environmental Toxicology and Chemistry of Oxygen Species, Springer-Verlag Berlin Heidelberg, 1998.
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  11. McFeters G.A.: Drinking water Microbiology, Brock-Springer, 1990.

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