TYPES OF BIOREMEDl AT10N

Bioremediation can be broken down into four categories:bacterial remediation, mycoremediation,phytoremediation, and compost bioremediation.

BACTERIAL RENEDIATION Bacterial remediation is the process of using bacteria to break down molecular contaminants like hydrocarbons into simpler, safer com­ponents. It can be accomplished by culturing (breeding) bacteria in high numbers and then introducing them into a contaminated area, and/or by turning the affected soil into an ideal habitat for bacterial growth.

Large numbers of beneficial bacteria can be introduced into soil by brewing something called composttea or through use of a prod­uct called Effective Microorganisms.

THE ECOLOGY OF BACTERIA Bacteria are simple, single-celled organisms found in abundance in almost all regions of the world. They are found in diverse environ­ments, from extremes like the human intestine to bot oceanic sulfur vents. A single teaspoon of healthy garden soil contains over a bil­lion of them. Although often associated with disease, most bacteria are not harmful to humans. Many are essential to human health. Ten percent of human body mass is made of bacterial cells.’

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Bacteria may be aerobic (oxygen using), anaerobic (non-oxygen..3.)

using), or somewherebetweell the two on an overlapping continu­um. Aerobic bacteria are typically found in healthy soil. Anaerobic bacteria are found in low-oxygen environmentssuch as pond muck,

,~~poorly maintained compost piles, and intestinal tracts. While some anaerobes are pathogenic (disease-causing) organisms, many, like acidophilus and lactobacillus, are essential to effective human di­

. .gestion. ,

COMPOST TEA Compost tea is a waterbased, oxygen-rich culture containing large populations of beneficial aerobic bacteria, nematodes, fungi, and protozoa, which can be used to bioremediate toxjns. It is made by adding an inoculant and a food source to non-chlorinated water and aerating it. The microorganismspresent in the inoculant rapidly multiply when put in oxygen-rich water with ample food. This brew is applied to contaminated soil, where the microbial populations go to work breaking down certain types of molecular contaminants. The ease and low cost of making compost tea make it a method of bioremediation with the potential for widespread application.

. THE COMPONENTS OF

COMPOST TEA INOCULANTS

A cup ofworm castings make an ideal ihoculant for compost tea. The castings can be harvested from a worm composting box or bought from a specialty nursery. Worms have no digestive acids in their stomachs. Instead, they use bacteria to break down food. Worm excretion is an excellent fertilizer in itself, rich in beneficial bacteria, fungi, protozoa, and nematodes. Another inoculant choice is aerobic comuost. teeming with microbial life. It is important for

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the compost to have been well-made, or few beneficial critters will be present.

B e inoculant is put into a nylon stocking that is suspended into the water. This allows the microbes to enter, but prevents the pas­sage of larger objects that could clog a sprayer's screen filter during application.

FOOD Rapidly reproducing organisms need food to fuel their cellular &vi­sions. Microbial foods are added to compost tea to help the process along. The most commonly used foods are molasses, humic acid, and fish hydrolase. The molasses, which should be unsulfured, is widely available at grocery stores. Humic acid and fish hydrolase, both fertilizers, need to be purchased from garden stores.

Molasses primarily feeds bacteria, while humic acid and fish hydrolase feed fungi. Bacterial teas enhance annual gardens, while trees prefer fungal teas. A mixture of these foods will create a fin­ished tea with both bacteria and fungi, which is ideal for remedia­tion of contaminants.

WATER Chlorine, a powerful microbicide found in municipal water, will kill the microljial life being cultivated in compost tea. Whiie it is far preferable to use collected rainwater or healthy pond water, municipal water can also be dechlorinatedby allowing it to sit un­covered for at least 24 hours. Most of the chlorine will volatilize during thisperiod. Aerating the water speeds up the process.

AERATION Proper aeration is critical. As compost tea is being brewed, the population of microorganisms is rapidly expanding. Like humans, aerobic bacteria need oxygen for survival. ?here needs to be enough oxygen present in the water to keep the bacteria alive. If too little

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oxygen i s available, anaerobic organisms will beginto grow instead. Some anasrobes produce alcohol as a by-product, which is harmful to plants. A small aquarium pump connectedto an airstone will supply sufficient aeration for a 5-gdon batch of compost tea.

BREWING AND APPLYING THE TEA

T h i s simple recipe for 5 gallons o f compost tea can be multiplied for larger batches.

How to:

1.Fill the bucketwith non-chlorinatedwater. (If using tap water follow the instructionsabove first.) Water temperature is ideally between 55 and 80 degrees Fahrenheit. 2. Put the airstone in the bottom of the bucket, attach the air pump, and let it start to bubble. 3.Put the inoculant in the stocking, tie off the end and suspend it in the water. Squeeze the stockinggentlyto release the organisms into the water. 4. After an hour or so, add the food. 5. le t the whole brew bubblefor24 to 36 hours. After 36 hours, the microbesbeginto die, oxygen levels drop, and the tea can become dangerously anaerobic. If the tea received insufficient oxygen or too much food, anaerobic organisms will overcome the beneficial aerobic organisms. Itwill be obvious i f the tea went anaerobic, because it will stink! If that has happened, pour it out away from garden plants and start over. 6. Pour the mixture through a strainer to remove large debris.

APPLICATION Once the tea has been brewed and removedfrom the oxygen, it must be applied within four hours, before it starts to go anaerobic.

Supplies needed:

5-gallon bucket One aquarium pump with airstone (bubbler) K cup of food 1cup of inoculant One nylon stocking Wateringcan or backpack sprayer

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,

?he tea can be applied to the'soil pack sprayer.Applying to moist soilis rainstorm is aperfect time. Rememb that need to be put in an.envi it is dry,spray the ground with non&MorinafedMt& plying the tea. ,- ' .

If the tea is for,bioremediation,apply it conditioning*ere contarninationis not B concern,'ddu' ih$&V'rI %+th five to ten parts non-chlorinated water. ' . '

gallon on l$OO square , tion rate would'not be.

I'

, .

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EFFECTIVE MICROORGAN ISMS

Effective Microorganisms (EM) is a trademarked product made by several different companies. It is basically a liquid culture of microorganisms consisting of yeasts, anaerobic bacteria, and photosynthetic bacteria. There are many claims for EM uses, from enhancement of agricultural production to wastewater treatment and remediation of toxins. What sets it apart from compost tea is that EM bacteria are facultative anaerobes. Unlike the strictly aerobic bacteria found in compost tea, fac­ultative anaerobes can survive in both oxygenated and oxygen-lacking envjronments. ?his allows EM to be bottled with a long shelf life, unlike compost tea, which must be applied shortly after being brewed. EM microbes include the bacterium Iucto-

Ibacillus, which is found in our gastrointestinal tract and helps us digest dairy, and the yeast Succhurornyces cereoisiue, which is used to ferment beer. Containers of EM can be purchased at specialty nurseries or over the internet.

EM is a n effective alternative to chlorine bleach for mold abatement. It was used successfullyfor mold remediation in New Orleans following Hurricane Katrina. After leaks in mold-stricken homes were repaired and mold was scraped off of surfaces, EM was sprayed. The organisms in the EM competed for space on the sur­faces with the mold spores, and either slowed or stopped regrowth of mold.

Compost tea and EM differ in that EM only contains 8 to 12 types of organisms, while compost tea contains thousands. Compost tea’s diversity is what makes it desirable for use in remediating toxins-it is moie likely that one of those thou­sands of organisms will be able to break down a particular toxin.

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