The processing buiding will be 40 feet by 60 feet in plan and will house all of the refuse processing operations, the sludge thickener, and the refuse-sludge mixer. Bulky paper, rags, metals, glass, and other noncompostable material, about 25 percent of the incoming refuse, will be removed by hand sorting and magnetic separation and hauled to the Johnson City sanitary landfill for disposal. Two types of grinders, a rasping machine and a hammermill, each with a design capacity of about 8 tons an hour, are so placed that they can be used alternatively for comparison of efficiency and costs of operation and maintenance. The refuse at about 35 percent moisture content, after sorting and grinding, will be mixed with thickened sludge and water as needed to increase moisture to 50-60 percent for the windrow composting.

Initially digested sludge will be pumped from one of the two digesters for thickening and composting with the refuse. As more sludge is removed than received, the digesters gradually will be converted to concentrating tanks until essentially raw sludge is being pumped. Sludge will be thickened in a Permutit DCG Solids Concentrator to a moisture content of about 85-88 percent. Filtrate from the sludge thickener, along with wastewater from the compost plant, will be returned to the sewage treatment plant for processing.

The refuse-sludge mixture will be composted on a 5-acre area graded and stabilized with crushed rock. Windrows, deposited by dump truck, will be about 7 feet wide by 5 feet high and up to 230 feet long.

The active composting time in windrows will be 30-35 days with a maximum of 44 days. During this time the refuse-sludge mixture will be turned 5-10 times with a self-propelled loader. To maintain 50-60 percent moisture content in the composting mixture, water will be added as needed during the turning operation.

It is planned to use a portable shredder and rotary screen unit as the compost is loaded for transfer to the storage shed. The storage shed will be 60 feet by 200 feet in plan and will provide shelter for curing, air drying, and storing the compost. After composting, at least two weeks of curing in windrows will be provided during which the moisture content of the compost is expected to drop to about 25 percent. The estimated average daily production of compost is about 25 tons or 42 percent of the weight of incoming refuse.

Plant operation and research studies

The plant operation will be completely coordinated with municipal activities concerned with refuse collection and disposal and sewage treatment. The city will maintain its present sanitary landfill and sewage sludge treatment facilities for use as needed.

The full-scale plant is planned to demonstrate a windrow method of composting solid wastes which may have application for other communities of possibly 100,000 population or less. One of the objectives of the project is to study the economics of the process. Complete construction and operating cost data will be obtained and economic evaluation of the process will be made. Various methods of "cleaning up" the compost will be tried to remove bits of glass, metal, stones, rubber, leather, plastics, and similar noncompostable materials. Processing methods and duration of composting and curing will be varied with the findings of the two major research studies: pathogen survival in the compost and market uses and value of the product in an effort to speed up decomposition and thus reduce operating costs.

Based on the pilot-plant studies by PHS at Chandler, Arizona, it is expected that 30-day windrow composting will decompose 35-40 percent of the volatile solids. During this time the peak temperature at 10-inch depth in the windrow is expected to be 160-168 degrees F and a temperature of 150 degrees F or more will be maintained for 16 to 22 days. However, temperatures in the outer and bottom layers (possibly 2-4 inches thick) are expected to be less than 140 degrees F most of the time.

Routine analyses will be made on samples of raw wastes and compost for total solids, volatile solids, moisture, and pH. These measurements will serve both in plant control and in plant performance studies. Temperature, moisture, oxygen, and pH measurements will be taken routinely in the composting windrows so that turning schedules and moisture additions may be regulated. Multipoint temperature recording will be employed in an attempt to correlate timetemperature with pathogen destruction.

Certain chemical tests, principally for nitrogen, phosphate, and potash, will be performed periodically to assess the nutrient value of the compost. The value

of high nutrient wastes and of chemical fertilizer materials added to the composting mixture will be determined as they affect both the composting process and the nutrient value of the final compost. Small special windrows of different mixtures of wastes will be prepared and tested in connection with both the pathogen survival studies and the studies on market evaluation of the compost. To detect and permit the correction of any health or safety hazards or nuisance conditions, close observations of odors, dust, noise, flies, and rodents will be made throughout the plant. The extensive studies of pathogen survival probably will be conducted under a PHS contract with an educational institution starting soon after plant completion next spring. These studies will involve the direct enumeration of those indicator organisms and pathogens normally occurring in refuse and sludge in the raw wastes and after various periods of decomposition in the composting and curing processes. Selected pathogens, not normally occurring in measurable numbers in the raw wastes, will be inserted in the windrows in porous containers for determination of survival rates. Microorganisms will include vegetative and spore-forming bacteria, fungi, protozoa, viruses, and helminths, including some of the most resistant pathogens.

The agronomic studies of compost conducted by TVA will include greenhouse experiments and test demonstrations in plots of the application of compost for various purposes, and the development of marketing potentials for the compost. Tests will be conducted on bare areas such as highway cuts and strip mine spoil banks to assess the value of compost in preventing soil erosion and aiding revegetation on such slopes.

While the principal use of compost is expected to be as a soil builder or conditioner, tests also will be made with compost fortified with nutrients to create an organic-base fertilizer. Large-scale use of compost on farm and pasture land is not anticipated, but appreciable applications on gardens, parks, lawns, golf courses, and truck or specialty farms may be potential outlets. Other uses will be sought, such as compost utilization as poultry litter.

The demonstration composting plant operation is scheduled to continue through fiscal year 1972.

LIST OF REFERENCES

1. "Reclamation of Municipal Refuse by Composting." University of California, Sanitary Engineering Research Project, Tech. Bull. No. 9, Series 37, June 1953. 2. Gotaas, Harold B., "Composting-Sanitary Disposal and Reclamation of Organic Wastes." World Health Organization, Mono. Series No. 31, 1956. 3. Wiley, John S., and George W. Pearce, "A Preliminary Study of High-Rate Composting.' Proceedings-American Society of Civil Engineers, 81, Paper No. 846, December 1955.

4. Wiley, John S., and Janet T. Spillane, "Refuse-Sludge Composting in Windrows and Bins." Journal of the Sanitary Engineering Division, American Society of Civil Engineers, 87, SA5, September 1961.

5. Wiley, John S., and O. W. Kochtitzky, "Composting Developments in the United States." Compost Science, 6, 2, Summer 1965.

6. Knoll, K. H., "Public Health and Refuse Disposal." Compost Science, 2, 1, Spring 1961.

7. Wiley, John S., "Pathogen Survival in Composting Municipal Wastes." Journal Water Pollution Control Federation, 34, 80, January 1962.

8. Krige, P. R., "The Utilization of Municipal Wastes." Council for Scientific and Industrial Research, Pretoria, South Africa, Report No. 211, 1964.

Mr. VIVIAN. What is the total cost involved?

Dr. GARTRELL. The total cost of the plant is around $750,000 for the initial plant installation. It is being specially designed to meet some research needs so that we can study the effects of the process on pathogenic organisms. It is both a demonstration and a research project.

Mr. VIVIAN. Let me switch to the next question. You indicated that you intend to begin research again. Can you tell me how much money you expect to spend in the next few years?

Mr. WAGNER. There are continuing activities such as Dr. Gartrell has described under the program on which we have spend $2,700,000

to date. What we intend to start up again is an effort to see if we can find a way to get sulfur out of the stack gases that would be a part of the total program. We can supply you our best estimates, although right at the present moment we are assessing the current state of technology and we won't know what kind of projects we want to propose until we get that done.

(The information requested follows:)

TVA is currently spending a total of about $475,000 a year for air pollution control research, and is presently estimating an increase in this level of expenditures to an average of about $675,000 per year over the next several years. A considerable part of this research effort will be directed to the problem of extracting SO2 from stack gases; and if TVA's research uncovers processes for solving this problem which appear promising, it may want to go into a crash program which will increase the level of its research expenditures in this field substantially.

Mr. VIVIAN. Next question.

When you started this work on air pollution abatement in 1949 as I remember from your testimony, didn't you obtain a great deal of information from others who had built thousands of thousands of megawatts of power installations up to that point?

Dr. GARTRELL. Strangly enough there was very little information available to us. The initial designs of our power stations were based on the best engineering practices at the time. But the thing that brought the air pollution question into focus was the size of the plants that we were expecting to build and the size of the units. The economics of power generation indicated the trend would be toward larger units and more units at individual sites.

So, it was the much greater mass of combustion products that posed the problem.

Mr. VIVIAN. Has the commercial power industry done very much on the subject?

Dr. GARTRELL. Not up to that time.

Mr. VIVIAN. Why did TVA go into this field? Was it because you are in one of the least populous parts of the United States?

Dr. GARTRELL. Because we had an identifiable problem and felt that we should deal with it in the interest of the valley.

Mr. VIVIAN. Suppose the plant that you tried to build had worked successfully. What percentage of the sales cost of power would that have represented? When you amortized that cost through the sale of power, what fraction of the cost would that represent?

Mr. WAGNER. I believe, Mr. Vivian, we did not carry the experiment to that point. We developed the fact that it would be a rather expensive plant, a large plant.

One of the problems was that it would cool the stack gases so much that it would perhaps create an even greater air pollution problem because the stack gases wouldn't rise and the remaining pollutants in them would not be dispersed as effectively in the atmosphere as the hot gases. It was just one of those experiments that was tried, that didn't work, and we didn't carry it to the point of calculating its effect

on costs.

Mr. VIVIAN. You could do it with blowers run by additional power. If you were trying to recover sulfur, you might have done it by other means, but I am trying to get some idea of the economics of recovering sulfur in terms of a percentage of the sales cost of electricity.

68-240-66-vol. 1- -28