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Natural Buffers for Sludge Leachate Stabilization
Author(s) -
Makeig Kathryn S.
Publication year - 1982
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1982.tb02762.x
Subject(s) - leachate , trench , hydraulic conductivity , soil water , environmental science , buffer (optical fiber) , buffer strip , aquifer , dispersion (optics) , nitrate , soil science , groundwater , hydrology (agriculture) , geotechnical engineering , environmental engineering , geology , surface runoff , materials science , waste management , chemistry , engineering , ecology , optics , composite material , biology , telecommunications , layer (electronics) , physics , organic chemistry
Large quantities of sludge can be disposed of safely by burial in narrow trenches. This paper describes a study to quantify the amount of buffer area around a trenching operation that would allow for the natural soils to stabilize sludge leachate without threatening the ground‐water supplies of surrounding communities. A vertical buffer consists of a thickness of unsaturated soil below the base of the trench. Its thickness is calculated by comparing the cation exchange capacity of the soil with the exchangeable cations in the sludge leachate. Data from metropolitan Washington, D.C. consistently require a vertical buffer of less than 3 feet thick. A minimum of 3 feet of unsaturated soil is recommended as a margin of safety, although no specific studies were performed to reach this value. The horizontal buffer is a strip of land that must be maintained between the trenching operations and the site boundary. Its width can be more than two orders of magnitude greater than the vertical buffer. Its width is based on the nitrogen loading of the soil from the sludge and the mobility of nitrate in the upper aquifer based primarily on hydraulic conductivity and the characteristics of the sludge/soil interaction. An advection‐dispersion model predicts nitrate concentrations for various buffer widths, and is used in conjunction with a specified maximum allowable nitrate concentration to determine a minimum horizontal buffer under certain ground‐water flow conditions.