4. Conclusions
A simple field approach is presented to periodically measure and estimate the porosity of HSSF CW media through measuring the media voids volume comparing with the initial pre-treatment porosity. During wetland operating setup stage, media porosity, bacterial biofilm, and plant roots growth are dynamically in progress until reaching the operational steady state stage. The reduction in porosities for wetland beds are related to the development of reeds roots and the growth of attached biofilm on the bed media surfaces in addition to periodical accumulation of suspended matter. The HSSF CW media porosity values reached the steady stage after nearly 6 months from start of operation for the wetland system in this study. Through 218 days from start of operation, the porosity decreases by 16.94% for gravel media, 12.33% for rubber media, and by 9.01% for plastic media. This indicates that the plastic and rubber media have a clogging ability smaller than the gravel one. At the end of setup stage, porosity values were 0.358 for gravel media, 0.505 for rubber media, and 0.788 for plastic media. During the setup stage, the growth of planted reeds roots and the increase of bacterial biofilm attached to the media surface and plant parts, enhanced the pollutants accumulation, biodegradation, and the treatment efficiency. Total suspended solids had the highest treatment performance in the 3 studied wetlands (39–61%) comparing with relatively smaller treatment performance for both BOD (20–49%) and COD (19–49%). Through the wetlands setup stage, plastic media had the best treatment performance for BOD, COD, and TSS followed by gravel then rubber.