ABSTRACT
The aim of this study is to determine the effect of chemical coagulants on the sedimentation properties of activated sludge.
2 MATERIAL AND METHODS
Industrial commercial coagulants used in this study included: polyaluminum chloride (PAX 16), polyalu-minum chloride + iron (II) chloride (PAX 25), sodium aluminate (SAX 18), iron (II) chloride (PIX 100), iron (III) chloride (PIX 111) and iron (III) sulfate (PIX 113). The characteristics of the applied coagulants are shown in Tables 1-2. Studies were conducted using coagulants in each of the five measurement series. The scope of research
1 INTRODUCTION
Review of the literature shows that the activated sludge technology has experienced operational problems since its inception. Bulking sludge and foam formation on the surface of activated sludge reactors is a significant problem in biological wastewater treatment systems. Excessive and uncontrolled development of certain filamentous bacteria is an immediate factor in the bulking sludge phenomenon. Massive growth of filamentous microorganisms leads to disturbances mainly in the sedimentation process of activated sludge, and consequently reduces the efficiency of wastewater treatment. In addition, there are numerous operational difficulties such as problems with the recirculation of sludge, reducing excess sludge properties in the process of thickening and dewatering, as well as difficulties with scrapers in secondary clarifiers etc. The Sludge Volume Index (SVI) is an indicator of the deterioration of the activated sludge sedimentation properties. Bulking sludge, termed as poorly sedimenting sludge, is characterized by the SVI greater than 150 mL⋅g−1. It is assumed that bulking sludge does not occur at low values of SVI (Gerardi 2002, Jenkins et al. 2004, Przybyła et al. 2009, Naidoo et al. 2011, Guo et al. 2014, Kida et al. 2015).
