Saturday, 15 July 2006

Wastewater Re-Use in Soilless Environments.

R. Michitsch1, C. Chong2, R.P. Voroney2, and B.E. Holbein3. (1) Dalhousie Univ, 14-200 Court Street, Box 143, Truro, NS B2N 3H7, Canada, (2) Univ of Guelph, Guelph, ON N1G 2W1, Canada, (3) SUBBOR, Etobicoke, ON M8V 3Y3, Canada

Organic components constitute more than 70% of the 30 x 10 6 metric tonnes of municipal solid waste generated annually in Canada , and current recycling methods are proving inadequate to handle current waste generation levels. These residual products are ‘lost’ resources if not re-used and may pose a detrimental environmental risk if improperly disposed. More specifically, liquid organic wastes generated primarily from anthropogenic sources, such as municipal wastewater, landfill, anaerobic digestion and industrial leachates, or compost leachates and teas, contain soluble nutrients which can potentially be re-used for fertilizing plants.

The recent movement towards a zero-waste society has fostered research to evaluate the re-cycling and re-use of these waste products from both waste-reduction and nutrient-recovery standpoints. These liquid wastes (ie wastewaters) have successfully been used to grow a variety of plant species, such as turfgrasses, trees and shrubs, fruits and vegetables, grains and legumes, and flowers. However, most re-use applications have centered solely in soil-based applications, while research in soil-less environments, typically as hydroponic applications, has been lacking or conducted with variable results.

Hydroponic culture has widespread use in modern society, whether for intensively growing vegetable and horticultural crops, or trying to manage societal wastes as efficiently as possible. Its main advantages include decreased nutrient and labour requirements, and rapid crop turnover. This method of growing plants is also useful from a research and waste management standpoint, since the ability to quickly indicate problems or sensitivities to nutrient deficiencies (or toxicities) is realized due to direct contact of nutrients (in solution) with plant roots.

Specifically detailing research conducted with a wastewater generated from the anaerobic digestion of a primarily organic-based municipal solid waste source, and used as a supplemental nutrient source for plant production, the application of liquid waste re-use in soil-less environments will be outlined. Potential issues of liquid waste re-use from various treatment facilities and miscellaneous applications, such as computerized control and monitoring of liquid nutrient levels, will also be discussed.


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