A well designed and correctly sized bio-disk installations can solve sewage treatment problems for small and medium sized communities.
PMT Ecodisks™ have many advantages over other treatment processes:
The wastewater is pumped or flows by gravity to the first chamber of a three chamber primary tank constructed in-situ.
Primary sedimentation takes place in the primary tank prior to the clarified wastewater passing over weirs and discharging into the inlet line to the Bio-disk for the secondary treatment phase.
In the secondary treatment phase, the biodegradable matter in the wastewater is aerobically digested. The main components of the system are the rotating discs. These circular discs are mounted on a horizontal shaft which is connected by a flexible coupling to a small gear motor. An aerobic bio-film forms on the disc surface which is constantly fed with oxygen as the discs rotate. The film is maintained at a pre-determined thickness by the disc spacing and the rotation speed of the discs which sloughs off excess growth and introduces air into the wastewater. This ensures a high level of dissolved oxygen within the process stream and allows greatly reduced contact time.
Since the micro organisms are attached to the disks as a fixed film biomass, it is not possible to wash these out of the plant at times of excess flow. Sludge re-circulation is also not necessary.
The sloughed off bio-film is elevated by a lifting wheel with the treated wastewater to a lamella separator. The lamella separator is used for the clarification of the wastewater passing from the biological stage.
It consists of a sludge tank shaped as a hopper containing parallel plates mounted at an angle of 55º. The large surface area of the plates provide a quasi-laminar flow which enables the heavier particles of sludge to settle on the upper surface of the plates and the clarified water to move upwards along the lower side of the plates and slowly reach the outlet.
The sludge slides downwards into the sludge hopper where it settles. The sludge outlet is at the lowest point of the hopper. Settled sludge is periodically pumped from the hopper to the first chamber of the primary sedimentation tank where it consolidates with the primary sludge. This operation is fully automatic and controlled by a time clock.
In an Ecodisk™ Filter, the sloughed off bio-film is elevated by a lifting wheel with the treated wastewater to a 2m Hyrotech Drum filter. Prior to discharge, the wastewater passes through a 20 micron polyester screen on which the bio-film is retained. The bio-film is periodically removed by a high pressure spray pump and returned to the first chamber of the primary tank. This operation is fully automatic and controlled by a time clock.
Three bucket elevators are attached to the shaft of the Bio-disk unit. One elevator is positioned in a separate chamber at the inlet to the Bio-disk. This elevator is utilised to lift primary clarified effluent from the buffer zone in the primary tank into the first tank of the aerobic zone at a constant rate to buffer flow surges. The optional second bucket elevator is positioned immediately following the biological stage and is designed to re-circulate the flow back to the first section of the three stage primary tank where anoxic conditions occur and denitrification takes place and the third elevator is positioned at the outlet end of the shaft and is used to lift the mixed liquor up into either the lamella separator or the drum filter for clarification.
The clarified wastewater passes through an optional tablet chlorinator or UV disinfection system where disinfection takes place prior to discharge or storage.
The primary and secondary sludge is digested in the primary sedimentation tank prior to being periodically pumped out for dewatering or off-site disposal.