Abstract
The article presents the results of an experimental study on the clarification of biologically treated wastewater in a clarifier with a suspended sludge layer. The pilot plant was receiving effluent from trickling filters treating municipal wastewater. An experimental clarifier worked under steady-state conditions considering the influent characteristics and variable operating parameters in terms of flow velocities and height of the suspended layer. From the experimental dependences between different technological parameters it was found that the optimum range of the upward flow velocities providing a dynamic equilibrium of the suspended layer was 0.6–1.4 mm/s. Upward flow velocities below 0.5 mm/s can lead to sludge compaction at the bottom of the unit, while values greater than 1.8 mm/s may cause sludge washout. It was also found that higher suspended layer height values favor higher efficiency of the clarifier and can achieve suspended solids in the discharge of less than 5.0 mg/L; this height should be greater than 0.6 m Technological efficiency of the experimental clarifier was significantly higher than the conventional unit and was comparable with tertiary treatment technologies.
Highlights
Biological wastewater treatment is the main and most economical method of removing contaminants from wastewater, as it provides a deep decomposition of biodegradable substances based on the use of natural processes and catalysts
The lower limit is determined by hydrodynamic forces—when the hydrodynamic force of the upward flow on the biofilm floccules is less than the gravity of the particles, the layer is compacted and the sludge accumulates at the bottom of the clarifier with a suspended sludge layer (CSSL)
The increase in the sludge volume index (SVI) value along the height of the suspended layer (HSL) can be explained by a number of reasons, namely: the development of the denitrification process in the suspended layer and the release of gaseous nitrogen on the floccules of the biofilm; the accumulation of fine floccules in the upper part of the suspended layer and by various combinations of the above
Summary
Biological wastewater treatment is the main and most economical method of removing contaminants from wastewater, as it provides a deep decomposition of biodegradable substances based on the use of natural processes and catalysts. Various modifications of FFSs have been studied, mainly as a part of the third stage of wastewater treatment (promoting water reuse), especially in the aspect of the high-efficiency removal of biogenic compounds [5,6,7]. These systems have been thoroughly tested in terms of their technological efficiency and the kinetics of the physicochemical and biochemical processes taking place in the biological reactors with attached biofilm and accompanying objects [8,9]. Since in FFS reactors the processes of biochemical decomposition of dissolved pollutants take place and the separation of the suspended solids (often conglomerated in the coagulation process), such devices are often referred to as biofilters [4,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
