Aquatic Phyto-Systems (APS)
Aquatic phytosystems are principally used to process effluents of one form or another, though manufactured wetlands have been used successfully to remediate some quite surprising soil contaminants, including TNT residues. Though the latter type of application will be discussed in this section, it is probably best considered as an intergrade between the other APS described hereafter and the TPS of the previous. Many of the aspects of the biotreatment of sewage and other wastewaters have already been covered in the previouly and so will not be restated here. The major difference between conventional approaches to deal with effluents and phytotechnological methods is that the former tend to rely on a faster, more intensively managed and high energy regime, while in general, the stabilisation phase of wastewaters in aquatic systems is relatively slow. The influx and exit of effluent into and out of the created wetland must be controlled to ensure an adequate retention period to permit sufficient residence time for pollutant reduction, which is inevitably characterised by a relatively slow flow rate. However, the efficiency of removal is high, typically producing a final treated off-take of a quality which equals, or often exceeds, that of other systems. Suffice it to say that, as is typical of applications of biological processing in general, there are many common systemic considerations and constraints which will obviously affect phyto-systems, in much the same way as they did for technologies which rely on microbial action for their effect.
Many aquatic plant species have the potential to be used in treatment systems and the biological mechanisms by which they achieve some of the effects will already be largely familiar from the preceding discussion of terrestrial systems. There are a number of ways in which APS can be categorised but perhaps the most useful relates to the natural division between algae and macrophytes, which has been adopted, accordingly, here.
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