With a particular attention to the cooling water filtration issues, Cannon Artes developed its proprietary Hydraback® technology. Automatic Valveless Gravity Filters are in fact a technical solution that matches the simplicity of gravity filtration with a purely hydraulical backwashing. The result is a very simple unit with very high efficiency and low capital and working costs.
The operating principle of gravity filtration is the hydrostatic level of water on top of the media layer. The filter is arranged on three chambers: the first contains the filtration media, the second one the filtered water and the last one is used as a transfer chamber to move water from the first to the second (filtration) or from the second to the first (backwashing). The filtered water contained in the second chamber is in fact used to backwash the filter when the pressure drop reaches the set-point value.
The stages of the filtration can be summed up as follows:
While the raw water flows through the filling media the hydrostatic pressure increases and subsequently the water level in the relevant feed pipe goes up.
When the pressure drop across the media bed reaches the upper value corresponding to the highest level in the feeding pipe, water overflows into the discharge pipe through a siphon. In such way the flow within the vessel is reversed and the backwashing is operated in a very short time and with high capacities.
The backwashing water, containing the solid particles retained during the filtration process, is recovered in a dedicated basin and transferred to the sludge dewatering unit.
This innovative filtering technology has the advantage of being able to treat large flows of water with no energy consumption for backwashing operation. In fact no rotating machinery is required and no costs for spare parts.
This is further enhanced by the fact that no control equipment is required (automatic valves, flow-meter, regulating instruments, etc.). Even though in absence of any control equipment, the filter is operated without supervising personnel thus minimising the management and supervision costs.
In spite of the above features, upon specific Client’s requests, the filtration system can be monitored and controlled by a Local Control Panel or directly from the DCS.
Characteristics and Advantages
High efficiency in reduction of the suspended solids
Low operating costs
No cost for chemicals
No blower is required for backwashing
No backwashing pump is required
No control instruments is required
No storage tank is required for the backwashing water
Possibility of dealing with elevated loads by using double-filtration-chambers and different units in parallel