Land Treatment: A Technology
To Meet Municipal Wastewater Needs

By DAVE KOLTUN
Department of Energy & Natural Resources

A few years ago, Tuscola, Illinois was facing a local issue common to many Illinois cities — how to meet new federal standards on wastewater management in a cost-effective manner.

The Douglas County community of 4,300 could have upgraded and expanded its conventional treatment plant. In some cases, adding filtration, nitrification, and phosphorus removal process will represent the most cost-effective option. For Tuscola, such changes would have entailed an estimated capital cost of $6.6 million and a net annual operating cost of $197,000. Instead, Tuscola opted for a slow rate land treatment system. The capital cost of approximately $3.7 million was almost half the cost of a conventional system. The annual estimated operating cost of its new system ($101,000) is just about half of the conventional system, and with annual net crop revenue projected at $37,000, the net annual operating cost of Tuscola's land treatment system ($64,000) is one third the cost of the alternative.

This new system "will take care of our needs into the future," according to Alan Gilmore, Superintendent of City Services for Tuscola. Despite the need for some filtration design changes, Gilmore believes the land treatment system provides "excellent treatment." He also cites the "ease of operation, the simple design, and the self-renewing" concept as pluses.

Tuscola's experience is one example of a growing realization of the potential benefits of land treatment of municipal wastewater. As the technology has improved, several hundred wastewater operations around the country have adopted land application systems.

Adoption of land treatment in Illinois has been at a slower pace, in part due to some misconceptions regarding the applicability of soils and climate and the economics of construction and operation. Stephen John, an environmental planner from Decatur, acknowledges the major capital investments that many municipalities have made in conventional treatment systems. However, he believes that municipalities with aging systems or those with caps on lagoon systems should consider land treatment, especially since the operating costs are "so much less expensive" and "if properly used, a lot of benefits and opportunities" can be obtained.

Research has indicated that many of the soils in Illinois are suitable for land treatment. Economic variables, such as the reduction of federal grant funds for wastewater projects, have also become less favorable for conventional treatment facilities. As successful land treatment enterprises have become more widely known, this innovative technique has gained credibility as a viable alternative.

Jack Sheaffer, President of Sheaffer and Roland in Wheaton, sees "tremendous potential for land treatment in Illinois." In particular, he points out the potential for privatization, citing 25 private land treatment systems in the state. "Instead of polluting streams, nutrients in wastewater can be sold as fertilizer for cornfields. I believe (land treatment) will become a widely used method in the next decade."

What is meant by "land treatment"?

Land treatment refers to a process whereby wastewater, after sufficient purification, can be reused for a variety of purposes. Recycled water can be used to water lawns and golf courses, and for industrial cooling, recharging of aquifers, agricultural irrigation, and other related activities.

A wastewater treatment system must be designed to prevent certain wastewater constituents, such as heavy metals and synthetic organic compounds, from polluting surface water, groundwater, and soils. However, other constituents, such as nitrogen, phosphorus, and micronutrients, can have positive effects.

Under controlled application conditions and using standards consistent with the Clean Water Act, water containing these latter constituents percolates through the soil and is taken up by plants. Commonly grown field crops (e.g. corn, soybeans, wheat) and forage

February 1989 / Illinois Municipal Review / Page 13

crops (e.g. alfalfa, grasses, clovers) remove varying amounts of nitrogen and phosphorus from farmland. Using proper management practices, a land treatment system can replace these nutrients, and thereby promote farm productivity.

Types of Systems

Land treatment systems generally fall within three categories: the slow rate, overland flow, and rapid infiltration/aquifer recharge.

Under the slow rate process, partially-treated wastewater is purified as it percolates through the soil and vegetative cover. An overland flow system is frequently employed on soils with a very slow infiltration/percolation rate. The water is filtered by close-growing vegetation (generally water-tolerant grasses) and it flows over a gently sloping soil surface. A thin film of wastewater is generally applied, and the breakdown of waste materials occurs near the soil surface. In the rapid infiltration approach, wastewater is spread in basins and is treated as it percolates through the soil. It then drains naturally to groundwater, and in some cases to adjacent surface water. Moderately and highly permeable soils are most suitable to this approach.

A feature common to each of these systems is the incorporation of lagoons into the system design. Lagoons are valuable in providing storage capacity during winter and in facilitating preapplication treatment.

Ownership and management of a land treatment facility offer a number of options. The responsibility for site purchase, irragation equipment, employee recruitment, and other aspects of management can be retained by a municipal or public authority, or contracted out to a private developer or company in some combination.

A Note of Caution

Adopting and implementing a land treatment system can be a feasible alternative to conventional treatment systems. However, considerable research and evaluation are necessary before a land treatment system can become a reality. Dozens of variables must be considered and assessed, especially in terms of the effects that changing one factor would have on a host of other factors. Examining land treatment brings to the forefront the high level of interaction among the elements that comprise our ecological/environmental system.

The list of potential variables that one must take into account before deciding to build a land treatment system would include such factors as:

Site Evaluation —

— groundwater quality, direction, and rate
— soil composition, permeability
— storage requirements
— total land requirements
— climate, precipitation, wind
— topography, ground slope
— erosion and flood potential

Management —

— hydraulic loading rates
— pest control management
— vegetation

Wastewater Evaluation —

— contents of the wastestream

Public Health —

— crop and food chain impacts

Attention to this type of detail, though, is essential in determining feasibility and cost-effectiveness. In addition, it can lead to desired modifications in system design and management. Such changes can enhance the attainment of municipal goals and objectives, chief among which is protecting public health.

To obtain more information about land treatment systems and the potential applicability for your municipality, a Guide to Land Treatment of Municipal Wastewater in Illinois is available free of charge from the Illinois Department of Energy and Natural Resources, Information Clearinghouse, 325 West Adams, Room 300, Springfield, IL 62704-1892, 1-800-252-8955.

A more complete picture of the relevant factors involved in the land treatment process can also be gained from forms issued by the Illinois Environmental Protection Agency, Division of Water Pollution Control.

Conclusion

Recent regulatory requirements regarding wastewater treatment plants have placed an additional burden on local government units to develop plans to meet these standards. Land treatment offers a viable option for decision-makers to consider. With insights derived from the efforts of pioneering communities, and continuing advances in technology and management, there is every expectation that land treatment systems will gain increasing acceptance in Illinois and the nation in the future. •

Skelton, Luther W., Hinesly, Thomas D., and John, Stephen F., Guide to Land Treatment of Municipal Wastewater in Illinois. Illinois Department ot Energy and Natural Resources, Document No. 88/12, Springfield, IL.

"Land Treatment: Using Plant-Soil Ecosystems to Purify Wastewater and Recycle Resources," Illinois Department of Energy and Natural Resources, Springfield, IL.

Page 14 / Illinois Municipal Review / February 1989