Reprinted With Permission From: February, 2008 ADVANCING COMPOSTING, ORGANICS RECYCLING & RENEWABLE ENERGY 419 State Avenue, Emmaus, PA 18049-3097 610-967-4135 • www.biocycle.net Managing Storm Water WHAT’S THE PROBLEM? Is it storm water? Is it wastewater? What is In a nutshell, contamination. By virtue of some of the data collected in the best method to calculate flows at the site? annual storm water runoff monitoring These questions, and more, are answered in requirements on composting facilities OPERATOR INSIGHTS — imposed under the Phase 1 Nation- al Pollutant Discharge Elimination BioCycle’s new Operator Insights feature. Part I System (NPDES) program established in the 1990s — it is now apparent that Craig Coker rain falling on exposed composting windrows can pick up substantial amounts of pollutants. If discharged to receiving streams unmanaged, the pollutants have the po- NE OF the clearly recognized tential to cause water benefits of compost when used quality problems in Oas a soil amendment is its abil- those streams. These ity to increase the water holding ca- off-site losses present a pacity of the soil. This is due to the higher level of concern ability of compost to retain water. than a similar amount Yet, this same beneficial material, of the same compounds while being manufactured, is now in the compost itself believed to create water quality because water quality problems that require regulatory standards for some permitting and potentially expen- constituents (i.e. pesti- sive treatment systems. Unfortu- cides, metals) are set nately, there is a wide variety of at much lower levels state regulatory approaches to ad- than any standards for dress this issue; some regulate land application of storm water runoff from compost- Taking a manual grab compost containing ing pads as a wastewater, and some sample of runoff (left) at these compounds and regulate it as storm water. the wrong time may elements (Cole, 1994). The purpose of this two-part arti- result in pollutant Not surprisingly, the cle is to examine how storm water is concentrations that are not truly representative. constituents in com- produced at a composting facility, Sampling methods to offset this difficulty include flow- posting pad storm wa- what types of contaminants it might composite and time-composite samples, often collected ter runoff depend, to have, how is it being regulated and with automated sampling equipment (above). some extent, on the what types of treatment work to feedstocks being com- meet regulatory requirements. As a Those lessons learned are reflected in posted. Yard trimmings composting former composting facility operator these articles. facilities have long been thought to and state organics recycling coordi- Part I also kicks off a new BioCycle have the least potential for contami- nator, and now as a consultant, I editorial feature in 2008, “Operator nation due to the relatively clean na- have worked first-hand on calculat- Insights.” Appearing in every other ture of the feedstocks, i.e., least ing storm water flows, identifying issue, Operator Insights will examine amount of chemical and pathogenic pollutants, and determining the op- topics that site managers face in their contamination to start with (relative to timum management strategy. daily operations. manure, biosolids and food scraps). Yet 28 BIOCYCLE FEBRUARY 2008 runoff from these facilities has been water bound inside plant and animal cell Quantities Of Storm Water shown to be highly variable, containing walls, the presence or absence of forced There are several tools of hydrology potentially significant levels of nutri- aeration that tends to evaporate more and hydraulics available to calculate ents, soluble salts, Biological and Chem- moisture and whether the composting runoff quantities from various storm ical Oxygen Demand (BOD/ COD), tan- process uses supplemental irrigation events. Storm water management reg- nins and phenols from decomposing during active composting. A more ulations and programs have historical- leaves, herbicides, pesticides, fungicides coarsly textured mix, like yard trim- ly been focused on managing quantities and fecal coliform (probably from animal mings, will have less water holding ca- of storm water. These rules are often feces mixed in the yard trimmings). An- pacity than a more finely textured mix, based on what is called the “recurrence imal manure, biosolids and food scraps such as dairy manure bulked with saw- interval” of a storm; terms such as “25- composting facility runoff will likely dust. Leachate draining through a com- year, 24-hour” and “10-year, 1-hour” have higher levels of nutrients, organic posting pile will pick up soluble materi- storms are often used. acids produced during decomposition als (tannins, nutrients, salts) as well as The recurrence interval of a storm is and fecal coliform bacteria (Oregon small particulate matter created by the a statistical abstract, and mathemati- DEQ, 2004). Little data is available on decomposition process. It is a combina- cally is the inverse of its probability of other pathogenic microorganisms in tion of the tannic acids and the particu- occurrence in any given year. For ex- composting facility runoff. late matter that give leachate its char- ample, a “25-year” storm has a statisti- Potential impacts of these con- acteristic dark brown color. cal probability of occurring once every stituents on stream and river water Process storm water is precipitation 25 years (the inverse is 1/25, which quality are the same as, and in some cas- that falls on the site and contacts the equals 0.04, or 4 percent). Thus the 25- es more severe than, untreated dis- composting material without flowing year storm has a 4 percent chance of oc- charges of sanitary wastewater. BOD through the pile. This includes runoff curring in any given year. Similarly, a and COD exert an oxygen demand on the from the sides of the pile as well as storm 10-year storm has a 10 percent chance dissolved oxygen in water, which if de- water that comes in contact with waste of occurrence and a 100-year storm has pleted will cause significant aquatic eco- material and compost that has strayed a 1 percent chance of occurrence. It is logical mortalities. Widespread fish kills from the pile. Nonprocess storm water is worthwhile to note that these statisti- are the most obvious of these problems. precipitation that falls on the compost cal abstractions can be misleading. Nutrients contribute to the geomorpho- site, but that doesn’t come into contact Many people think that if a storm has logic process known as eutrophication, with wastes or compost. Wash water is only a 4 percent chance of occurring where nutrients support the growth of generated by washing vehicles and (i.e. once every 25 years), it is unlikely algae, which also deplete oxygen upon equipment and contains materials dis- to occur more frequently. It is entirely their deaths, as well as stimulate the lodged from vehicle wheels and bodies, possible that two 25-year storms can growth of vegetation (this is an accelera- but the concentrations tend to be lower occur in the same year, or even in the tion of the natural process by which shal- due to the high volumes of dilutive water same week or month. low watercourses become swamps, and used in washing. On the other hand, A “24-hour” storm is the total in turn, eventually become dry land). wash waters can contain surfactants amount of precipitation that falls in Tannins and lignins are natural dis- and other chemicals from any washing 24 hours, which, for example, is 6.5 solved organic acids that give water the detergents used. Run-on is rainfall inches here in western Virginia. Simi- characteristic color of compost tea. Phe- runoff from uphill of the composting site larly, a one-hour storm is the amount nols are a group of related acidic com- that flows through the site and comes in of rain falling in one hour (about 2.2 pounds that are hydroxyl derivatives of contact with wastes or compost. En- inches here). However, storm water aromatic hydrocarbons. These include closed composting facilities also have management systems are based on such substances as cresol, catechol, condensate — water that evaporates both volumes of storm water as well as quinol, xylenol, guaiacol and resorcinol. from the compost and condenses on cool- flow rates of water to be managed, so There are two effects apparent in phe- er surfaces such as building walls. a storm of one hour duration with a nol-contaminated waters: toxicity to rainfall intensity of 1.5 inches per aquatic life and the generation of an un- HOW MUCH RUNOFF? hour will produce the same volume of pleasant taste in fish and shellfish. Figuring out how much storm water rain (1.5 inches) as a storm of six hour There are different sources of water runoff will have to be managed at a com- duration but only one-quarter contributing to runoff from a composting posting facility is not an exact science. inch/hour rainfall intensity. That 1.5 facility and each is subject to different lev- Rainfall varies in intensity both in space inches of rain will produce a volume of els of potential contamination. Ordered and in time, as evidenced by the intensi- 54,450 cubic feet of rainfall (about from most to least potential for contami- ty of a thunderstorm on one side of a 407,000 gallons) on a 10-acre concrete nation, they are: leachate, process storm road, but not on the other. Similarly, or asphalt composting pad. Not all of water, nonprocess storm water, wash wa- runoff quantities vary as a function of that rain becomes runoff. ter and run-on. “Runoff” is generally a how much rain has fallen recently, pos- Flow rates are measured in volumes mix of leachate, process storm water, sibly saturating the ground, as well as per unit of time (for example, cubic wash water and nonprocess storm water.