HYDRAULIC LOADING FOR LAND TREATMENT SITES
UNDER NON—IDEAL CONDITIONS
Tammo S. Steenhuis, Assistant Professor
Raymond C. Loehr, Professor
Department of Agricultural Engineering
Cornell University
Ithaca, New York 14853
Chris Babajimopoulos, Assistant Professor
School of Agriculture
Aristotelian University
Thessaloniki, Greece
INTRODUCTION
Treatment of municipal and industrial wastewaters has become an effective waste management
option. Land treatment removes suspended solids, biodegradable organics, microorganisms, almost
all of the applied phosphorus and, with proper management, most of the applied nitrogen.
Land treatment systems are site specific. The technical and economic feasibility of land treatment
will depend on: (1) the waste characteristics; (2) transmission distances from the waste source to the
treatment site; and (3) the site topography, vegetation, soils and hydrogeology. The interactions
between these facts must be considered in identifying and using suitable sites.
The engineer is to collect the information and to design the most cost effective and technically
sound system. Specifically the engineer must: (1) identify technically feasible land treatment sites
located within the feasible transmission distances; (2) identify the most cost-effective options for use
of such sites; and (3) collect the necessary field data for preliminary and final design preparation. The
liquid hydraulic application rate is one of the most important design considerations for land treatment
systems treating wastewater. Of importance is the movement of the applied wastewater not only
through the surface soils but also through the subsoil. With sites that have a relatively high groundwater table or perched water conditions due to less permeable subsoils, the lateral or horizontal water
movement through the soil can be as or more important than the vertical movement of the applied
water. Experience has indicated that there are many soils that have the above conditions.
To assist in the design of land treatment systems, a design methodology to determine: (1) proper
hydraulic application rates; and (2) the impact of the applied rates on groundwater table height and
movement has been developed. The methodology follows the general design principles presented by
Loehr and co-workers [1,2]. The methodology is a state-of-the-art approach that: (1) integrates many
factors involved in the design of land treatment systems; (2) can be used as a screening procedure for
preliminary evaluation of land treatment feasibility and in final design development; and (3) is
designed to be used on a microcomputer. The methodology developed in this paper for hydraulic
loading is tailored especially to the type of microcomputer now widely available in engineering offices.
The design procedure is divided into three parts. The level I analysis is a general evaluation which
includes a problem definition and an initial solution definition and limitations. It is meant to screen
out site and treatment alternatives which are clearly not feasible. Level II analysis permits a more
detailed analysis of potential site and treatment options and should define a solution to the waste
treatment problem. The level III procedure develops a final solution design.
This paper has two objectives. The first is to identify the methodology that can select the proper
hydraulic loading of a land treatment system for wastewater. The methodology considers the effect of
the additional recharge on the existing hydrological system. The second objective is to incorporate the
use of microcomputers in the design process. Microcomputers not only reduce the tedious and time
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