An ecological engineering system model applied to the case of an integrated agro-industrial complex
Intensive stock breeding namely swine, beef and dairy cattle and related activities are characterised by an enormous pollution potential. Without suitable treatment, this kind of waste with high levels of organic matter, nutrients, heavy metals and pathogenic microorganisms originates air, water, soil and food chain contamination. The removal or the reduction of the pollutant matter contained in the wastewater, to levels respecting the European standards, generally imposes, in the classic way, the implementation of heavy, sophisticated and expensive engineering procedures yet still fallible. These procedures or the uncontrolled dispersion of the stock breeding waste in nature represent, besides the described nuisances, an important loss in terms of energy and of the discarded materials that can be either recycled or reused.
In order to help solving this kind of problems and to get some advantage from the by-products or from the waste, ecological engineering or ecotechnological systems can be used. They include combined production systems and they involve (Shijun and Jingsong, 1989) a set of treatment operations and processes, the regeneration and the cycling of the residues, wastewater and by-products as part of a semi-artificial ecosystem. Valuable final products are obtained.
The present work simulates the homeostatic mechanisms of an ecosystem in order to adjust the structure and operation of an hypothetical semi-artificial, steady sate balanced ecosystem. However, this system still integrates some conventional and confined engineering techniques.
Constructed wetlands and wastewater advanced treatments, still uncommon in Portugal, are also considered. Besides the design parameters, the wastewater treatment sub-system dynamic modelling is performed, considering several: types of production, flow rates, efficiencies, final concentrations and mass and energy balances, along the year, under different abiotic conditions.