The use of fabric filters, also called belt filters, is becoming more common in greenhouse horticulture. They're useful for the filtration of rinsing water from sand filters and self-cleaning filters, along with filtering drain and basin water. Discharging rinse water is therefore no longer necessary. With the continuously operating filter technology, solids can be removed from liquids. This is done by allowing water to run without pressure over a filter cloth which collects contaminants. The filter cloth is a horticultural fleece fabric made of polyester, viscose-polyester or polypropylene.
Special filter technology
Aqua D & S has developed a unique flatbed fabric filter with a special filter technique (patent pending), which filters up to 5 microns. Placing the filter cloth over a water-permeable bottom with obliquely raised edges means that there is no leakage and contamination in the filtered water. Depending on the amounts of fine dirt in the water, the cloth will compact after a certain amount of time and the water level will rise, with a level switch activating the transport motor and the contaminated cloth moving up a segment. Eventually the canvas ends up in a collection bin and can then enter the waste container. In addition to a capacity of 7 or 14 m3/hour of this maintenance-free cloth filter, there is now also a new XL type with a capacity of 21 or 28 m3/hour.
Combination with ultra-filtration
Due to this thorough pre-filtration, the treated water is suitable for disinfection with ultraviolet (UV) or ultra-filtration (UF). All the rinsing water that is generated by a grower can be filtered with the fabric filter and be reused after disinfection. With this filtration technique there is no more rinsing water. "When our fabric filter is combined with the ultra-filtration, you are 100% guaranteed free of fungi, bacteria and viruses," says Richard Feijsman of Aqua D & S. Ultraviolet light only kills the micro-organisms. Ultra-filtration (which filters up to 0.011 microns) captures them, so they no longer end up in the pipe system. As a result, virtually no biofilm will build up in pipes in the future.
Multiple fabric filters
There are several suppliers that offer various fabric filters for greenhouse horticulture. Moor Filtertechniek supplies another type of flatbed belt filter with capacities from 3 to 60 m3/hour.
ECOfilter supplies a deep bed cloth filter where the filter cloth and two wheels on the side of the filter cloth form a filter bowl. Through the force of gravity, the water flows into the filter bowl through the filter cloth. The fabric filter is available in four capacities of 16, 34, 80 and 100 m3/hour.