Chemical composition and flocculation efficiency were investigated for a commercially produced tannin - based coagulant and flocculant (Tanfloc). The results of Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive Spectroscopy (EDX) confirmed what claimed about the chemical composition of Tanfloc. For moderate polluted municipal wastewater investigated in both jar test and pilot plant, Tanfloc showed high turbidity removal efficiency of approximately 90%, while removal efficiencies of BOD and COD were around 60%. According to floc size distribution, Tanfloc was able to show distinct performance compared to Polyaluminum chloride (PAC). While 90% of flocs produced by Tanfloc were smaller than 144 micron, they were smaller than 96 micron for PAC. Practically, zeta potential measurement showed the cationic nature of Tanfloc and suggested coincidence of charge neutralization and another flocculation mechanism (bridging or patch flocculation). Sludge Volumetric Index (SVI) measurements were in agreement with the numbers found in the literature, and they were less than 160 mL/g. Calcium cation as flocculation aid showed significant improvement of flocculation efficiency compared to other cations. Finally Tanfloc showed competing performance compared to PAC in terms of turbidity, BOD and COD removal, floc size and sludge characteristics.

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Constructed wetlands attracted the attention of researchers as a sustainable, economic, and efficient wastewater treatment technique. Many papers showed the efficient performance of constructed wetlands to treat municipal, industrial, livestock, petroleum, and other types of wastewater, effectively removing organic matters, phosphate, nitrogen, and contaminants of emerging concern such as pharmaceuticals and antibiotics. There have been numerous reviews in the literature that studied nitrogen removal in constructed wetlands from different perspectives. However, the majority are concerned about the conventional nitrification process. It is worth mentioning that some biological nitrogen pathways other than the conventional nitrification process were implemented in constructed wetlands efficiently such as partial nitrification and denitrification, simultaneous nitrification and denitrification, anaerobic ammonium oxidation, and completely autotrophic nitrogen removal over nitrite which have been reviewed in this study. The outcomes of this study showed that anaerobic ammonium oxidation is the most common pathway applied in constructed wetlands. Moreover, this review showed that the efficient performance of these novel pathways is constrained by the difficulty of controlling the operating parameters such as dissolved oxygen, temperature, and pH.