Biosolids are an unavoidable bi-product of sewerage treatment.? However, through careful treatment, Biosolids can be recycled and used effectively as fertilizer and compost as as for combustion processes.? Water must be removed from sludge in order to minimize transportation costs as well as to render it suitable for agricultural or combustion purposes.? This form of sludge is described as sludge “cake.”
Sludge Treatment Processes
The sludge undergoes digestion, a heating process which destroys the bulk of present pathogens prior to passing through large dryers and a pelletizer.? Alternatively, the sludge is “lime stabilized.”? The addition of CaO (lime) to sludge results in a exothermic chemical reaction which eliminates pathogens.
Gauge Location and Installation
Gauge location is dependent on the Treatment Process, however, installation above a belt conveyor, if possible, is simple and effective.? In order to improve measurement performance, the installation of a doctor blade prior to the gauge location, helps to break up and spread the cake solids over the belt, thereby presenting a fresh surface of product to the gauge.? Implementation of two doctor blades (one perpendicular to belt direction and another obluque to the blet) to channel product onto a transfer conveyor will provide the best results.
The % solids readout can be used to control the centrifuge, press and dryer operation as well as the rate of lime addition where applicable.
Measurement accuracy is dependent on the composition of the sludge and how variable it is over time, also on the % solids level.? In most instances, however, the % solids reading is accurate to within +/- 0.5%.