The impact of sewage composition on the soil clogging phenomena of vertical flow constructed wetlands.

The infiltration rate and therefore the principal function of a sand based vertical flow constructed wetland (VFCW) is influenced by the content of suspended solids (SS) and chemical oxygen demand (COD) of the waste water supply. In this study there were three operating conditions defined as "No Clogging"; "Partly Clogging" and "Clogging". Investigations on 21 VFCWs approved analytical differences between these conditions. The content of SS and especially particles > 50 microm are considered to play a key role. These particles are of the same size as the pores in which seepage mainly occurs. Thus their potential for surface blocking is high. It is concluded that the construction and size of the primary settling has to ensure that the mean concentration of SS after settling does not exceed 100 mg l(-1). The results of this study indicate that the area of the VFCW should be designed for a maximum loading rate of 5 g m(-2) d(-1) and the COD load should not exceed 20 g m(-2) d(-1).

[Threatened fibula fracture by transosseous migration of a leaded glass fragment]. / Drohende Fibulafraktur durch transossäre Wanderung einer Bleiglasscherbe.

A case of a 24-year-old man is reported: At the age of ten he was injured by a pane of glass in the region of the medial ankle joint. 14 years later a piece of broken glass which was overlooked during wound toilet, had penetrated to the lateral ankle. The foreign body was impacted in the distal fibula which was sensitive to pressure. Our case shows the importance of a careful inspection of every wound. An unrecognized foreign body may cause severe complications later on.