CONTINUOUS BACKWASH FILTRATION
The feed water is fed into the filter at the base of the active sand bed through the distribution ring. It then flows upward through the downward moving sand bed where the solids are filtered out.
The clean filtrate exits the filter through the overflow weir while the continuous reject flow of washing water is discharged through a separate outlet.
The dirty sand is continuously removed from the active sand bed thanks to the action of the air-lift pump. This pump draws the contaminated sand from the bottom of the filter body. A mixture of sand, dirty particles and water is transported upward through the air-lift pipe into the washing chamber at the top of the filter.
The separation of impurities from the sand takes place in the unique washing system. This separation is achieved using the action of a countercurrent stream of water injected at the bottom of the washing chamber. The sand is returned by gravity to the top of the active sand bed after being routed downward through a labyrinth of settling steps.
| Main Features and Benefits
▪ absence of any mechanical moving parts
▪ unique continuous back-wash system uses feed water for counter-current sand washing
▪ simple plant with no backwash water storage and backwash pumps
▪ higher suspended solids content in feed, high efficiency in removing fine solids
▪ colloidal particles efficiently removed through simple in-line dosage of coagulants
▪ coagulation, flocculation and filtration in one step thanks to the deep active bed
▪ very low pressure drop across the filter, gravity feed is possible in many instances
▪ easy maintenance thanks to the fully external sand air-lift system
▪ easy and simple installation
▪ low capital cost
▪ negligible operative costs
▪ simple modular construction can match any capacity requirement
| Typical Applications
▪ Pulp and Paper: polishing of process waters for recycling
▪ Oil Refining: oil removal from waste waters
▪ WWTP: tertiary treatment; phosphorus removal
▪ Iron and Steel: oil and scale removal from cooling waters
▪ Metal Finishing: metal hydroxide removal from wastewaters
▪ Water Supply: potable water filtration, algae removal
▪ General: -boiler feed water pre-treatment, cooling tower water clarification, membrane ultra-filtration and ozonization plant pre-treatment
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