 This film describes a research program supported by grants from the National Science Foundation. It focuses on the management of sludges from community wastewater treatment plants. The coordinated projects are presented in a way to suggest assessment of an integrated system consisting of disinfection, pipeline transport to a suitable site, and direct injection into soil. The research on disinfection with energized electrons was jointly supported by the Environmental Protection Agency and the National Science Foundation. Even before there was written history, people crowded into cities and created the problem of what to do with the wastes city dwellers produce. Take the congested cities of England during the Industrial Revolution. Public sanitation? Just about nonexistent as garbage and body wastes were thrown into the streets or the nearest water channel. Raw sewage ran openly through many cities. Thousands died from water-borne diseases such as cholera and typhoid fever. Not only in England, but in American cities too. Sewers originally built to drain storm runoff were gradually converted into drains for wastewater. Today, the health hazards remain. Many of the pollutants that are discharged into wastewater are concentrated during treatment in sludges, and the problem of where to put them is still with us. We're now disposing of some 35 billion gallons of sludge a year, and the amount continues to increase. Sludge contains all the pollutants and contaminants removed from wastewater. Toxic substances, pathogenic viruses, bacteria, protozoa, parasitic worms, all of which threaten our health and the ecosystem on which we depend for survival. As the commonly used sludge handling options, incineration or dumping at sea are becoming impractical or undesirable, land applications emerging as the only other alternative. And researchers are experimenting with new and imaginative techniques for placing sludge on land. The principle that guides the research is that sludge must and can be managed in an ecologically sound way through the use of appropriate technologies. From an ecologist's standpoint, sludge may be considered nothing more than the waste products of one group of organisms, humans. The human waste can act as the food for a host of other organisms, mainly bacteria. Thus, sludge added to soil can be consumed by soil microorganisms. It can also enhance the condition of the soil and the growth of crops by providing essential nutrients such as nitrogen and phosphorus. Used in this way, sludge is a link in the food chain that runs in an endless circle from humans to soil to plants and animals and to humans again. But to take advantage of this potential resource, we must learn how to manage the placement of sludge on land safely. A research project to do this is under the direction of Dr. James Smith of Colorado State University. A lot of the natural soils in Colorado look like this. They're clay-y, not much organic matter, and sometimes they can be just as hard as a brick. Now, in this part of the field, we have essentially the same soil, but with a difference. This has been treated with municipal sewage sludge using a new technique which we've developed at Colorado State University in cooperation with the City of Boulder and a local engineering firm. Quite a remarkable difference. The dramatic difference in soil quality is the result of a technique developed by researchers here which uses a specially designed plow that injects sludge directly into the soil. Sludge supplied to the unit is distributed through a manifold to several hoses. Each hose is attached to a heavy steel shank. At the bottom of each shank is a sweep that makes a cavity six to eight inches beneath the surface. To show how the injector unit works, sludge is allowed to spray onto the surface. In normal operation, the flow of sludge is started after the sweeps are underground. Thus, odors are minimized, and the land looks much like a plowed field. Sludge can be delivered to the site by pipeline before being injected into the soil. During an eight-hour day, this unit could inject the sludge from a city of 300,000 people in the 12 acres of land daily. The amount of land actually needed for this hypothetical city would depend on local conditions such as climate and soil characteristics. Environmental conditions on and under the field were monitored during the several years the research was in progress. The effect of sludge on the quality of the groundwater was of special concern. Sludge application could infect a field with pathogenic organisms or contaminate it with heavy metals. In the course of research, hundreds of samples were taken of both the water that percolated through the soil and the groundwater itself. In addition, crops were grown in soil injected with sludge to find out how plant growth and crop yield would be enhanced or otherwise affected. All samples were then taken to the laboratory for analysis. To detect the presence of cadmium and other heavy metals in the water or plant samples, researchers used an atomic absorption spectrophotometer. The presence of cadmium and other heavy metals may limit the application rate of sludge to land, but perhaps these substances could be eliminated at their source. The feasibility of doing this is being investigated by Gernamin Associates, a consulting engineering firm in Chicago. Researchers also wanted to discover what happened to the nitrogen applied along with sludge because of the nitrogen's value as a plant nutrient. Some of the nitrogen was converted by microorganisms into nitrates, which are undesirable pollutants when present in groundwater in excessive amounts. Therefore, the amount of nitrogen applied to soil may also limit the rate at which sludge is applied to land. We think that subsurface injection or the direct application of sludge into the soil is a very promising way for managing municipal sewage sludge. It's simple, economical, and has relatively few limitations. One obvious limitation is that we can't operate very effectively in frozen ground. However, with good management, there's no reason why the system can't be used by many cities. Provided we can solve a few remaining questions. One is the possibility of a health threat from diseases caused by protozoa, bacteria, viruses, and intestinal worms that may be concentrated in sludges during wastewater treatment. One of the research teams investigating possible health threats is headed by Dr. Bernard Sajik of the University of Texas at San Antonio. A major portion of our effort in the laboratory is concerned with the survival of viruses applied to soils and domestic wastewater and sludges. We're concerned about several virus diseases being spread by contaminated groundwater, minor ones, and one major one, infectious hepatitis. There are a lot of questions unanswered. We'd like to know what makes a virus flow through the ground, what makes a virus survive in soil, what mechanisms are involved in virus inactivation. To answer these and other questions, Dr. Sajik and his associates designed a series of experiments that duplicated natural conditions as much as possible. Samples of wastewater and activated sludge were collected, as were samples of soil. In a model reactor, a known quantity of tagged virus was added to the samples to simulate the normal content of virus in wastewater. As the viruses circulated within the reactor, some of them became associated with sludge particles. Sludge containing the indicator virus was then applied to soil cores proportionate to the amounts that would be injected into soil under normal operating conditions. Then to discover how long viruses applied to soil might remain a health hazard, researchers simulated many environmental conditions, including varying amounts of rainfall or irrigation, and different temperatures. Water that percolated through the cores was then collected and analyzed for its content of live virus. All of our results so far point to one conclusion, and that is that domestic sludges injected into the soil pose a potential hazard to groundwater supplies. Enough viruses do survive, especially in cold climates, for far longer periods than we'd originally thought. This leads to the inescapable conclusion that we have to reduce the level of virus and sludge prior to injecting it into soil. To do this, another research project is underway at the Metropolitan District Commission's Deer Island Treatment Plant in Boston. It's aimed at eliminating viruses and other pathogens from sludge by irradiating sludge with a beam of energized electrons. The research is a joint effort that involves universities, private industry, local, state, and federal governments. The work centers around a test facility and the main goal is to deal with sludge on a realistic scale. The facility was built after two years of preliminary research at the Massachusetts Institute of Technology had shown that irradiating sludge with energized electrons killed viruses and other pathogens in sludge. Dr. John Trump is in charge of the research. The idea of using ionizing energy, such as the gamma rays of radioactive materials, or the ionizing energy produced by streams of high-energy electrons has been around for one or two decades. But it's only in the last years that it has become clear that this is indeed a most effective way of disinfecting municipal sludge so as to make it safely usable on land for a variety of purposes. The irradiation system is surprisingly simple. The electron beam power supply is capable of generating almost a million volts used to accelerate electrons toward their target. A concrete enclosure houses the heart of the system, the electron accelerator and scanner. Behind the concrete shield, the electron accelerator directs a powerful beam of electrons through the scanner at a layer of sludge flowing beneath it. Sludge, or any other material that can be piped in from the treatment plant, is presented in a thin layer so that every bit of material is irradiated in a fraction of a second. The toughest problem researchers have had to solve here is to present sludge to the electron beam in a uniformly thin layer so that no part of the sludge escapes the minimum dose needed to kill viruses and other pathogens. This unit can irradiate 100,000 gallons of sludge a day, the amount produced by a city of 200,000 people. The seven-foot-thick concrete enclosure surrounding the radiation chamber absorbs x-rays produced when the beam hits a target. The absorbed energy from a disinfecting dose of 400,000 rads only raises the sludge temperature by one degree centigrade. Scientists from both MIT and the University of New Hampshire are involved in assessing the effectiveness of the electron treatment on bacteria, viruses, and other pathogens. Many key experiments begin with the addition of a known quantity of virus, usually polio, to the sludge flowing through the system. The intense electron beam causes the sludge to fluoresce. The high-energy electrons penetrate the sludge and accomplish their work in a fraction of a second. In each experiment, sludge samples are irradiated at several dose levels. Finally, a sample that received no electron treatment at all is taken as a control, and the samples are transported to the laboratories of the University of New Hampshire. This is where all the virological studies in connection with the Deer Island project are done. Dr. Ted Metcalf is in charge of the research. Our objective here is to determine how effective energized electron treatment is in killing enteric viruses, that is, viruses that pass through the human gut and that are found commonly in sludge. Viruses are incredibly potent packages of infection, so we need to make sure that any treatment that we give sludge is indeed effective in eliminating viruses as a health hazard. Before virus content can be determined, viruses must first be recovered from the irradiated sludge samples in a special solution. Viruses are true intracellular parasites. They can reproduce only within living cells. For this reason, cultures of living cells are used in these experiments. A healthy, normal cell culture looks like this, a smooth, even layer of adjoining cells. To test for the presence of active viruses, the cell cultures are inoculated with especially prepared samples. Each cell culture is then stained with a dye that makes living cells turn red. Colorless patches or plaques will form where the cells were infected with living viruses. After inoculation, the cultures are incubated to give viruses a chance to replicate. Several days later, the colorless plaques of infected dead cells are counted. The more viruses present in a given sample, the more plaques. From these experiments, a clear picture of the effectiveness of sludge irradiation has emerged. At zero irradiation, there was nearly 100% virus survival. As the radiation dose increased, the percentage of surviving viruses decreased in proportion. At a dose of 400,000 rads, no virus survived in digested sludge. What we really should say is, no virus survived that we can detect. Some viruses, like infectious hepatitis and gastroenteritis viruses, cannot be recovered routinely in cell culture systems. Nevertheless, everything we have learned today indicates that these viruses will be killed by radiation just like others that we can recover. What this means is we have a method here that will virtually eliminate viruses as well as other pathogens in sludge as public health problems. Clearly, the treatment of sludges by energized electrons has the potential of being an economical and environmentally safe technique for disinfection when used as part of an integrated system of sludge management. Our previous concern was with possible danger to humans. What we might also ask, how does the soil ecosystem react to sludge application to land? If we elect to use land application for sludge management, its compatibility with the soil ecosystem is essential. Assessing this compatibility is one of several research projects being conducted at the Soil Invertebrate Laboratory of the College of Environmental Science and Forestry in Syracuse, New York. The work is under the direction of Dr. Roy Hardenstein. Soil is a very complex ecosystem which is inhabited by numerous creatures, including a wide variety of earthworm species. Now that sludge application to land is being considered very seriously, we have to ask ourselves whether that application is going to do harm to the land and its inhabitants. And on the other hand, how can we use the soil organisms to manage the sludge most efficiently? Part of the research was aimed at finding out whether earthworms survived when allowed to feed on different types of sludges and sludges mixed with soil. In one series of experiments, a carefully weighed quantity of earthworms was placed in dishes containing various sludges. The dishes were set aside to allow the worms to feed on the materials. After a time, the condition of the worms was checked. Early experiments show that some sludges were very toxic to worms, killing them within hours. The toxic sludges had all been anaerobically digested. On the other hand, worms thrived on sludges that had been aerobically digested. As they passed the material through their bodies, large, tough clumps of sludge were broken up into castings which are similar to topsoil. As a result of this laboratory research, a practical experiment to do this is now underway at the San Jose Wastewater Treatment Plant in California, Dr. Hartenstein. We've really just begun to learn how earthworms may be helpful to us in managing our very serious sludge problem. For example, we have strong evidence that the earthworm is very effective in reducing the number of salmonella and other pathogens that are present in sludge. Also, once sludge has passed through the animal's body, the castings which the animal has now produced are totally devoid of odor. What it amounts to is that we have many more options open to us to manage our sludge than we had previously thought. With many treatment techniques available to the designer of wastewater treatment plants and considering the wide range in wastewater composition, the question for the plant designer and operator becomes which mix of options will work best and be most economical? This question is being investigated by Dr. Richard Dick and his associates, working first at the University of Delaware and now at Cornell University. Present practices were developed by engineers with an urgent need to solve sludge management problems. The work we are doing differs from much of the work of the past in that we are basing design and process integration on the best fundamental understanding of process performance we can develop. There's a great need for improved economy and effectiveness in sludge management. Modern digital computers make it possible to take into account the complex interactions between processes so that we can evaluate how best performance and economy can be achieved. To illustrate how this works, let's consider a city of 75,000 people. They would produce a wastewater flow of about 10 million gallons a day. Let's treat that wastewater by primary sedimentation and the activated sludge process and treat the sludges produced from primary and secondary treatment by gravity thickening to increase their concentration, anaerobic digestion to stabilize the sludge, and then apply it to agricultural land. Let's consider that it's trucked 20 miles. For this illustration, we have constrained the size of the gravity thickener to 1,000 square feet. This would be a rather traditional design value for a city of this size. The resulting cost of sludge management, including amortization of capital, is $366,000 per year. Now, let's tell the computer not to fix the size of that thickener by the traditional criteria, but rather to pick the size which gives least overall cost for sludge management. In this case, the size of the gravity thickener is 1,700 square feet. That's a 70% increase in the size of the thickener and it's going to cost more, but that extra expenditure is more than compensated by the savings in the cost of other processes with which the thickener is integrated. In this case, the total annual cost for sludge management will be $250,000 or a savings of $116,000 each year. Results of this research can be useful to planners, consulting engineers, managers at wastewater treatment facilities by showing the implications of alternative sludge management approaches. Until recently, putting sludge on land had been considered an undesirable and even unsafe practice from the public health standpoint. The viruses and other pathogens in sludge could make it a link in a chain by which disease might be transmitted from infected to healthy people. We now have the means to break this cycle of disease transmission and to reduce potential health risks. Thus, disinfection of sludges by energized electrons, followed by direct injection into soil, may provide us with an acceptable, technically superior and more economical method for sludge management.