Wastewater in the Brewery – Are You Sending Money Down the Drain?
Dana Johnson, Birko Brewery and Produce Specialist
The New Brewer, July/August 2008
Brewers know that it takes a lot of water to make potable water to make beer. Even in the most efficient breweries, the ratio of gallons or liters of water to actual beer produced is about 4-5:1. In breweries that are not as efficient in conserving the amount of water used, the ratio can be as high as 6-8:1 or even higher.
So what happens to all of the water that does not make its way into the beer? In some breweries, the water is recycled or re-used in some way but in most breweries, the water simply goes down the drain – oftentimes without any kind of pretreatment. What is pre-treatment of brewery effluent, you ask? This article will detail the growing trend of wastewater becoming an issue for craft breweries, and the governmental regulations that craft breweries need to be aware of to stay on the right side of the law.
Before we dive in (no pun intended) to the wastewater discussion, a few definitions of commonly used terms regarding wastewater are helpful to know.
pH: In layperson’s terms, the measurement of how acidic or alkaline the wastewater (or any aqueous solution for that matter) using the pH scale of 0-14. Anything below pH 7 is said to be acidic, anything above 7 is alkaline or basic, and of course a pH of 7 is neutral. In more technical terms, pH traditionally has been defined as a measure of the hydrogen ion concentration. Perhaps a better way to look at it would be to say that it is a measure of the ratio between hydrogen ion (acid factor) and hydroxyl ion (base factor). Hydrogen ion equals hydroxyl ion at pH 7. As you move from pH 7 to pH 8 the hydroxyl ion is ten times more concentrated than the hydrogen ion. At pH 9 the hydroxyl ion is 100 times greater than hydrogen ion. Conversely as you go from pH 7 to pH 6 the hydrogen ion is ten times greater than the concentration of hydroxyl ion. As you move away from pH 7 each pH unit represents another tenfold increase in the ratio between hydrogen ion and hydroxyl ion concentrations. pH measurement is one of (if not the most important) items to monitor before sending wastewater down the drain.
BOD: Biochemical Oxygen Demand. Most water has oxygen dissolved in it. If there are living organisms in that water they will absorb some of that oxygen to sustain their metabolism. BOD tests measure the rate of depletion of oxygen by microorganisms from the water over a specified period of time. The time period (in days) is typically indicated by a numerical subscript after BOD. If there is no oxygen in the water it will not sustain aerobic life. Anaerobic organisms can live if there are chemical compounds such as sulfate present that the anaerobes can use as their oxygen source. In other words, sterile water in a closed container just sits. The oxygen content remains stable. Now add some bacteria-maybe they will consume oxygen, maybe not-it depends on food. Natural waters contain “food” for bacteria.
Polluted waters also contain “food.” If both bacteria and food are present, oxygen will be consumed. The BOD test deliberately adds sewage bacteria to water of unknown organic composition to see how much oxygen gets consumed beyond the control levels. If “pollution” is present that can be oxidized by bacterial action, it is measured by the quantity of oxygen consumed and is expressed as “mg/L of oxygen consumed.” This number represents the total of biologically oxidizable substances in the water. This number then is related to COD which measures the content of “all” (chemically) oxidizable substances present in the water. The resulting ratio gives you a measure of what percent (%) of the pollution present can be oxidized by the sewage bacteria. The test is clumsy, inconvenient, and not very precise, takes too long, (5 day and 7 day tests), BUT it is the one biological measure that we have to see how badly a sample of water is polluted. That is why it still is in use-nobody has figured out a better method yet.
COD: Chemical Oxygen Demand. Certain chemicals, such as reducing agents will react with oxygen. The COD is a measure of the total oxygen that can be consumed by all the impurities that are present in the water sample. A very fast test (2 hours max.). A chemical reaction employing chromic-sulfuric acid oxidizes organics and gives you a direct measure of the amount of chromic oxidizer that is consumed. The result is expressed as “mg/L of COD” and represents the total of chemically oxidizable substances in the water sample. The BOD is related to this number to get an idea of how much of the COD can be removed from the water by sewage plant treatment.
TSS: Total Suspended Solids total suspended solids. Most water has some insoluble particles floating in it. The TSS test passes a known quantity of water through a 1.5 micron filter. The weight of the particles trapped on the filter is calculated out as a ratio of particles to water-usually expressed as ppm, although sometimes it is expressed as percent if there is a high level of solids in the water.
TDS: Total Dissolved Solids. Technically it is the ratio of solids to the total weight of water in a sample that has been evaporated to dryness. However, in water samples where the bulk of the dissolved solids are present as salt it is common practice to express a conductivity reading of this water as TDS. Conductivity meters that provide TDS readout are commonly used in many industrial processes. Conductivity meters are actually measuring the ionic strength of the solution – its ability to conduct electricity between two electrodes separated by the solution being measured. The traditional, low-tech approach is to dry a known mass of polluted water and then weigh again after the water is gone. This is the more accurate method but is slower. The problem with conductivity is: (a) it detects only ionic substances; (b) not all ionic substances generate the same amount of conductivity (c) conductivity is a sensitive function of temperature. If you had a carbohydrate-rich solution (think sugar plant effluent) conductivity would fail to detect most of the sugar present.
FOG: Fats, Oil, and Grease. Brewery soil by itself does not contain a lot of FOG but the restaurant side of brewpub can contain foods that have a lot of FOG. Lard, cooking oils, high fat dairy products, butter and margarine, bakery items, sauces, etc. can all contribute to the FOG in wastewater. FOG can lead to plumbing blockage problems not only within the restaurant but in the pipes leading to the POTW, (like a clogged artery) leading to sewage back-ups. The best way for FOG to not be a problem is remove the FOG from entering the drain in the first place.
Heavy Metals: Heavy metals are those metals whose properties are defined by the arrangement of electrons that fill the d orbitals in the 4th, 5th and 6th rows of the periodic table. These metals tend to form coordination compounds (as opposed to ionic compounds) and have more than one coordination state. They, also, frequently form complexes with chemical groups such as the ammonium ion. Think especially mercury and lead. Both accumulate in the body with time and are very difficult to dislodge once they are in. Mercury seems especially to affect the nervous system. The best way to attack this subject is to list what water districts ask you to analyze for: cadmium, copper, chromium, hexavalent chromium, lead, mercury, molybdenum, nickel, zinc, arsenic, silver and selenium. Curiously enough, however, copper, molybdenum, zinc and selenium are required for life but in relatively small or tiny amounts and can be toxic at low doses which is why water analyses include them. For most breweries, heavy metals should not be an issue unless a soft metal like copper is getting dissolved by caustic and getting into the wastewater.
Cleaning Up Your (Wastewater) Act
Many small craft breweries in the United States do not monitor their wastewater going down the drain. “We’ve never been checked” is a common response when asked what type of treatment program these breweries have in place to pre-treat their wastewater before allowing it to go down the drain to the city.
Unfortunately, the days of dumping whatever you want down the drain are probably numbered, especially in the bigger cities that have older wastewater treatment facilities called POTW’s (Publically Owned Treatment Works) that are struggling to keep up with the wastewater they receive. The easiest way that brewers can get in compliance with federal and local wastewater regulations is to neutralize the pH of the effluent by installing some type of neutralization tank such as an old fermenter or tank to contain the wastewater before it goes down the drain. Using an old unitank (cylindroconical fermenter) it will also allow some of the solids to settle at the same time as well. By simply allowing the wastewater time to sit before going down the drain, much of the solids such as spent grain, yeast, trub, brewery soil can settle out and not contribute to the BOD and COD load going down the drain. Even if you are on a septic system, you don’t want to overload the organisms with too much soil but you don’t want to starve them out, either. A balance needs to be achieved to keep the septic system operating efficiently. In larger breweries, these same types of organisms can actually work for the brewery and can actually save money in utilities (more on this later).
Most small breweries, however, really do not need to get sophisticated equipment to pre-treat their wastewater, unless they choose to either out of a desire to save money on wastewater surcharges or to be as environmentally friendly as possible. Unless you are looking at complying to strict local wastewater limits, it probably will not pay for you to install a lot of expensive wastewater equipment to handle your wastewater. What follows are some low cost methods that can help brewers get their wastewater in compliance with regulations
pH controllers typically add either sodium hydroxide or sulfuric acid to raise or lower the pH to the 5-9 range. The advantage of a pH controller is that they can be installed in line so the chemical is added to the water as it is moving through a pipe before it goes to a holding tank or down the drain. Getting the pH neutralized is the single most important step that brewers can do to get their wastewater under compliance with regulations. Most local wastewater districts like to see a pH in the range of 6-9 but sometimes they do allow higher pH because it will get neutralized before reaching the POTW. Too much acid going down the drain can be a problem, especially if the sewer pipes are concrete. Acid can dissolve concrete and that is big reason that the pH needs to be neutralized in addition to the fact that the organisms at the wastewater treatment plant tend to operate more efficiently in a more neutral pH range. Conversely, too much caustic can be a problem for the same reason as well – the pH can be too high for the bacteria in the wastewater treatment facility to operate efficiently.
Filter Bags/Filter Cartridge
Using a filter bag will get the gross soil (sometimes referred to “feathers and beak”) out of the wastewater either before it goes to a holding tank or down the drain. The advantage of this type of system is that it is affordable, easy to maintain, and does not take up a lot of space in the brewery. Filter cartridges are also affordable but can plug easily if the soil blinds the filter. If the cartridge method is used, it is best to do a series of them rather than relying on one cartridge to do all of the work. While filter bags and cartridges are not intended to greatly lower the TSS, they can remove a lot of the contaminants that contribute to BOD and COD.
Wastewater chemicals such as aluminum sulfate (often referred to as “alum”) and polymers are often used to help either precipitate or float solids. Alum helps float fatty acids by allowing them to attach to the alum so they can be skimmed off. Polymers have varying molecular chain lengths that attach to solids and either float or sink to the bottom so they can be skimmed, drained, filtered, or centrifuged. This type of chemistry is typically used for high water volume of users that have some resonance time to allow for the settling or flotation. For this type of chemistry, special equipment also has to be installed to either skim off or remove the solids, depending on what type of contaminant to be removed from the wastewater. For larger breweries, centrifuging the water to remove solids can be employed but centrifuges tend to be out of the price range for smaller craft breweries but if you are ready to take this step, consult with a wastewater treatment company.
Why Should We Care?
Even if your brewery has not been currently doing anything to pre-treat the wastewater, it would behoove you to do so, if nothing else but to stay ahead of the governmental regulation curve. True, you might not have the local wastewater district knocking on your door but as your brewery grows or if you plan to move to a new location, there will more than likely be more focus on the brewery wastewater in the new facility. Because of population increase and aging sewer systems, many new POTWs will need to be built in the coming decades in the U.S. and the rate payers are going to be asked to foot some of the bill to construct them. My advice: Save yourself some aggravation and headaches by preparing for that now, rather than later. You’ll be glad you did.
Author’s note: I would like to thank Terry McAninch and Victor Reusch, chemists at Birko, for helping me with the definitions for this article.