STELLA software as a tool for modelling phosphorus removal in a constructed wetland employing dewatered alum sludge as main substrate

A dynamic simulation model was developed for the removal of soluble reactive phosphorus (SRP) from the vertical flow constructed wetlands (VFCW) using a dynamic software program called STELLA (structural thinking, experiential learning laboratory with animation) 9.1.3 to aid in simulating the environmental nature and succession of relationship between interdependent components and processes in the VFCW system. In particular, the VFCW employed dewatered alum sludge as its main substrate to enhance phosphorus (P) immobilization. Although computer modelling of P in treatment wetland has been well studied especially in recent years, there is still a need to develop simple and realistic models that can be used for investigating the dynamics of SRP in VFCWs. The state variables included in the model are dissolved phosphorus (DISP), plant phosphorus (PLAP), detritus phosphorus (DETP), plant biomass (PLBI) and adsorbed phosphorus (ADSP). The major P transformation processes considered in this study were adsorption, plant and microbial uptake and decomposition. The forcing functions which were considered in the model are temperature, radiation, volume of wastewater, P concentration, contact time, flow rate and the adsorbent (i.e. alum sludge). The model results revealed that up to 72% of the SRP can be removed through adsorption process whereas the uptake by plants is about 20% and the remaining processes such as microbial P utilization and decomposition, accounted for 7% SRP removal based on the mass balance calculations. The results obtained indicate that the model can be used to simulate outflow SRP concentration, and it can also be used to estimate the amount of P removed by individual processes in the VFCW using alum-sludge as a substrate.Other funderDepartment of Agriculture, Fisheries and Food12M embargo: release on 1/06/2012 - AV 25/08/201

Constructed wetlands for environmental pollution control : a review of developments, research and practice in Ireland

For the purpose of synthesizing a compendium of efforts aimed at environmental pollution control through the use of constructed wetlands systems (CWs) in Ireland, a detailed review of CWs was undertaken. Emphasis was placed on the diverse range of development, practice and researches on CWs technology, placing them in the overall context of the need for low-cost and sustainable wastewater treatment systems. The potential use of CWs in protecting estuarine quality within the current legislative framework is considered, as well as the emerging concept of integrated constructed wetlands (ICWs). In addition, an assessment of the efficiency of CWs in operation in Ireland towards abating environmental pollution was done, and compared with CWs operating in other European countries. The need for sufficient and appropriate data to assist in further development of CWs and modelling studies, and instilling confidence in the public is also highlighted.Other funderEnvironmental Protection Agencyti, ke,-SB01/09/201