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- Effect of vegetation on the performance of horizontal subsurface flow constructed wetlands with lightweight expanded clay aggregatesPublication . Mesquita, Maria da Conceição; Albuquerque, Antonio; Amaral, Leonor; Nogueira, ReginaThis research evaluates the effect of both organic and ammonia loading rates and the presence of plants on the removal of chemical oxygen demand and ammonia nitrogen in horizontal subsurface flow constructed wetlands, 2 years after the start-up. Two sets of experiments were carried out in two mesocosms at different organic and ammonia loading rates (the loads were doubled); one without plants (control bed), the other colonized with Phragmites australis. Regardless of the organic loading rate, the organic mass removal rate was improved in the presence of plants (93.4 % higher for the lower loading rate, and 56 % higher for the higher loading rate). Similar results were observed for the ammonia mass removal rate (117 % higher for the lower loading rate, and 61.3 % higher for the higher loading rate). A significant linear relationship was observed between the organic loading rate and the respective removal rates in both beds for loads between 10 and 13 g m(-2) day(-1). The presence of plants markedly increase removal of organic matter and ammonia, as a result of the role of roots and rhizomes in providing oxygen for aerobic removal pathways, a higher surface area for the adhesion and development of biofilm and nitrogen uptake by roots.
- A poly-Ꜫ-caprolactone based biofilm carrier for nitrate removal from waterPublication . Rodrigues, A. L.; Machado, Ana; Nóbrega, J. Miguel; Albuquerque, Antonio; Brito, A.G.; Nogueira, ReginaNitrate removal from water has been accomplished by heterotrophic biofilms using organic carbon as a source of reducing power. To overcome the natural limitation in organic carbon in water, a poly-epsilon-caprolactone based biofilm carrier that serves simultaneously as a biofilm carrier and as a source of organic carbon was developed and tested in the present work. The feasibility of the new biofilm carrier for nitrate removal from water was evaluated in a packed bed reactor. The combination of size and structure provided a carrier element having high surface area and void volume, 1,170 m(2)/m(3) and 67 %, respectively. A maximum denitrification rate of 4.4 mg N-NO3-/(L.h) (9.2 mg N-NO3-/(m(2).h)) was achieved in the packed bed reactor at 20 degrees C and pH 7.0. Main advantages of the biofilm carrier developed in the present work are its mechanical stability in water even after biofilm formation and controlled release of organic carbon by enzymatic reactions. The proposed biotechnology to remove nitrate from groundwater is robust and easy to operate.