SCREEN FILTERS.
Screen filters come in different mesh (holes per square inch) this filters are used to insure that a certain particle size is kept out of the water you irrigate with. Example drippers are usually clogged with particles greater than 120 mesh, so we put a filter with a screen of 120 mesh that will eliminate all particles greater than 120 mesh

Screen filters come in single screens or double screens. The quality of the filter is measured by the surface size of the screen available, the larger the surface of the screen the more filtration takes place. The filters are made of plastic or steel of course the steel filter s are stronger and more expensive but may be cheaper in the long run. Some have wash out valves, and some have automatic clean out devises. Screens are made of stainless steel or plastic, there are screens made of other materials for industry , most screens are stainless or plastic. Plastic screens change mesh with use and have to be checked periodically to make sure that the mesh is maintained, stainless steel screens keep their mesh but can be damaged.

Screen filters should not be used when the contaminated water has organic material especially alleges, filaments will weave their way inside the screen and eventually clog the screen.

The major thing to remember is that screen filters do not clean water they let only a certain size of contaminant to pass into the irrigation water.

DISC FILTERS.
These filters are similar to screen filters but more efficient. They are build of a stack of discs that are allowed a fixed amount of separation and the water passes through this separation leaving the particles greater than the passage in the discs. The discs have to be cleaned periodically. There are automatic back wash disc filters, they should not be used with organic material. Some manufacturer recommend using this filters for organic material, the literature and The AMERICAN WATER WORKS ASSOCIATION do not recommend it.

CENTRIFUGAL FILTERS.
Centrifugal filters causes the water to turn inside the filter at a relative fast speed, by doing so it creates a centrifuge. In a centrifuge particles that are heavy move to the outside wile the lightest particles remain in the center,. Using this principle this filters can eliminate material that have a specific gravity larger than water, such as sand, or other contaminants that are heavier than water. This filter are very efficient and can prevent a lot of wear and tear on your irrigation equipment. The most efficient of those are the hydrocyclone separators see table of actual test.

Particle Size	Water to be Filtered number of particles	First Filtration number of particles	% Reduction	Second Filtration number of particles
1 to 5 microns	212,012,800	81,472,800	72	43,778,400	80
5 to 10 microns	5,148,800	3,222,400	48	1,009,600	74
10 to 25 microns	416,000	260,800	48	35,209	92
Over 25 microns	8,800	6,100	31	0	100
TOTAL	217,586,400	84,472,800	61	44,823,200	80

The amount of particles removed depends on the number of turns per seconds occurring inside the filter, pressure and volume passing trough the filter influence the speed of those turns. It is recommended that there be at least 50 psi pressure and use the gpm recommended by the manufacturer.

MEDIA FILTERS.
MMedia filters are specifically made to remove organic material and improve water quality. To understand the way they work we have to understand how water is penetrating into our aquifers. Media filters can be single media or multi media. Media filters are a container with influent entrance an under drain and an effluent exit. Between the influent and effluent media is placed for the water to penetrate, the media should be as close as possible uniformly in size. Single media filters are usually rapid filters and are used to eliminate large filament like algae and commonly use gravel.

Let us explore some of the media available and their recommended use. The most common used media is sand or silica. This particular media is measured effectively by the percentage silica oxide in the sand. It is also important to find out either the media is angular, semi round to round, or round. The round media has a higher life spend and can save labor the rounder the media the more it cost, so it is a management decision to figure out cost of media versus cost of labor. The media comes in different sizes and can be used to obtain different quality of water, depending on the size of the media.

Garnet is used as a lower layer of gravel because they have a high density and therefore do not mix with the silica during back wash performance. Garnet refers to several different minerals alamandite an andradite that slicated iron, aluminum and calcium mixture. Some suppliers use spessartite, which contain chromium or ilmenite an iron titanium mineral and others it is important to have a knowledgeable supplier in this field, one of the best is George L. Troop Co, in Pasadena. The thickness of each layer of gravel should be at least three times the maximum particle size of the gravel in the layer, but not less than 3".

Manganese Greensand is used primarily for the removal of iron bacteria and hydrogen sulfide from water. This is a non proprietary media is processed glauconitic greensand on which a shiny, hard finite thickness of manganese oxide coating is formed. The manganese is than converted to manganese oxide with potassium permanganate. Manganese greensand contains 0.3% manganese or 0.45% manganese dioxide.

These media is in use for the past 50 years and is unequalled in performance. The filter has to operate at 5 GPM/sq. ft. of media for water with moderate concentration of iron. It is recommended that you call an expert before you set up your filtration system, so the right size filter is used.

Anthracite is a hard natural coal of high luster differing from other coals by containing little or non-volatile mater. Anthracite can reduce some heavy metal from the irrigation water. In a nursery in Canyon Country we were able to reduce Boron by a small fraction so it could be used for irrigation of nursery material. Anthracite comes in many effective sizes from 0.6mm to a high of 1.6mm with a uniformity coefficients of 1.7 or lower.

The last media we will discus is activated carbon, this is a material with is high content of carbon. This material is produced by grinding the row material and adding a binder to give it hardness. The resultant is a product with a very large surface area. One pound of activated carbon is equivalent to the surface of six football fields. Because of these characteristics it can absorb a lot of contaminants from the water such as chlorine or other chemicals.

The important think to remember is that a solution can be found to each problem. If you accept that there is no single solution to all water quality problems.

In large reflecting pools and lakes aeration and water movement are very important. The equal movement can be achieved by using many drainage areas trough out the pool instead of a single point . In any case have at least one ventury point to vacuum the pool, have the flow from that point go directly into your pre filter, and than to your media filter. The media should be fairly small and the filter should be figured to 50% capacity only. Our office will be glad to work with you on specifications or design as the case may be.