Dynamics of sulphur compounds in horizontal sub-surface flow laboratory-scale constructed wetlands treating artificial sewage.

The knowledge regarding the dynamics of sulphur compounds inside constructed wetlands is still insufficient. Experiments in planted (Juncus effusus) and unplanted horizontal sub-surface-flow laboratory-scale constructed wetlands fed with artificial wastewater were carried out to evaluate the sulphate reduction, the composition and dynamics of generated sulphur compounds, as well as the influence of carbon load and plants on processes of sulphur transformation. In planted and unplanted wetlands, the addition of organic carbon (TOC of about 120 mg L(-1)) immediately affected the transformation of up to 90% of the incoming sulphate (150 mg L(-1)), directing it mainly towards elemental sulphur (30%) and sulphide (8%). During this experimental period, nearly 52% of the transformed sulphate-sulphur was calculated to be immobilized inside the planted wetland and 66% inside the unplanted one. In subsequent experiments, the deficiency of organic carbon inside the planted wetlands favoured the decrease of elemental sulphur in the pore water coupled to retransformation of depot-sulphur to dissolved sulphate. Nearly 90% of the deposited and reduced sulphur was found to be reoxidized. In principle, the results indicate a substantial improvement of this reoxidation of sulphur by oxygen released by the helophytes. Surplus of organic carbon promotes the ongoing sulphate reduction and the stability of deposed and dissolved reduced sulphur compounds. In contrast, inside the unplanted control wetland, a relative stability of the formed sulphur depots and the generated amount of dissolved sulphur compounds including elemental sulphur could be observed independently of the different loading conditions.

A step towards decentralized wastewater management in the Lower Jordan Rift Valley.

In order to address serious concerns over public health, water scarcity and groundwater pollution in Jordan, the expansion of decentralized wastewater treatment and reuse (DWWT&R) systems to small communities is one of the goals defined by the Jordan government in the "Water Strategy 2009-2022". This paper evaluates the general potential of decentralized wastewater system solutions to be applied in a selected area of the Lower Jordan Rift Valley in Jordan. For the study area, the connection degree to sewer systems was calculated as 67% (5% in the rural sector and 75% in the urban sector). The annual wastewater production available for DWWT&R in the rural sector of the investigation area was calculated to be nearly 3.8 million m(3) at the end of 2007. The future need of wastewater treatment and reuse facilities of the rural sector was estimated to be increasing by 0.11 million m(3) year(-1), with an overall potential of new treatment capacity of nearly 15,500 population equivalents (pe) year(-1). The overall potential for implementing DWWT&R systems in the urban sector was estimated as nearly 25 million m(3) of wastewater in 2007. The future need of wastewater treatment and reuse facilities required for the urban sector was estimated to be increasing at a rate of 0.12 million pe year(-1). Together with the decision makers and the stakeholders, a potential map with three regions has been defined: Region 1 with existing central wastewater infrastructure, Region 2 with already planned central infrastructure and Region 3 with the highest potential for implementing DWWT&R systems.