HYDRODYNAMIC ASPECTS OF PARTICLE CLOGGING IN THE SIMULATED VERTICAL FLOW CONSTRUCTED WETLAND USING RIVER SANDS AS SUBSTRATE

This paper introduced a simple method for evaluating and predicting the degree of clogging in simulated Vertical Flow Constructed Wetland (VFCW) based on hydraulic conductivity (k) measurement. This method was developed for better understanding of the deposition by the changes of k and the captured particles capacity in substrate void relation with both time and depth in the simulated VFCW filter bed. Additionally, in order to gain an insight into the clogging, the study put forward a VFCW hydraulic conductivity formula and then calculated the accumulated particles in filter bed according to two calculated approaches. The results showed that the most clogged location was the top layer (0-10 cm), the development of head loss in the VFCW was strongly correlated with the surface area of the captured particles from influent, the maximum change of the porosity occurred in the initial operation period, and the clogging process was progressed step by step. The paper reported the results of captured particles in filter bed void and presented an equation to calculate the predicting clogging time in VFCW

Phosphorus removal by laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate

This research aimed to investigate the phosphorus (P) removal of a series of laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate in treatment of low concentration domestic sewage. The long-term performance of P removal was firstly studied by using single substrate of anthracite or steel slag, and three systems applying various combined substrates were investigated when the average P loading rate varied between 0.9 and 1.5 g TP/m(2).d. The results demonstrated that both anthracite and steel slag systems were highly effective in removing total P (TP, 77.17 +/- 23.34% and 90.26 +/- 4.48%) and soluble reactive P (SRP, 92.14 +/- 12.56% and 96.20 +/- 2.58%). The system filled with anthracite, vermiculite and steel slag from the top down removed 82.45 +/- 9.52% and 87.83 +/- 8.58% of TP and SRP, respectively. However, other combined substrate systems showed comparative low and fluctuant P removal. The effluent pH was maintained at 7-9, which met environmental requirements of China. Therefore, anthracite provides a long-term high efficiency of P removal and may be a promising substrate from the standpoint of the effluent pH, and the arrangement of combined substrate has a prominent effect on P removal