The picture overleaf illustrates the various sizes of slow sand water filter media Express Drainage Solutions Kenya Limited can supply.
- Express Drainage Solutions Kenya Limited can supply any size of water filter media depending on the clients requests.
- Express Drainage Solutions Kenya Limited filter sand is sourced from multiple locations in Kenyan River systems, to ensure we consistently provide the ideal angularity, size, spherity and hardness for the most efficient filtering of water throughout all the seasons.
- Express Drainage Solutions Kenya Limited testing over a number of years has also proven that our filter sand has a slow breakdown rate.
- Express Drainage Solutions Kenya Limited ensures Triple Washing and screening of the Filter Sand to produce a quality filter medium.
- Our Express Drainage Solutions Kenya Limited sand filter media is natural and requires no pre-sizing because we have several natural collection sites with various sizes.
- The Express Drainage Solutions Kenya Limited filter sand is then dried and packed to your specifications.
- And because our filter sand is washed, dried, screened and packaged at the Express Drainage Solutions Kenya Limited, we can offer competitive prices and prompt delivery.
- The sample physical properties which we consider when selling are;
- Specific Gravity
- Loss on Ignition
- Effective Size
- Uniformity Coefficient
Express Drainage Solutions Kenya Limited , is a leading stocking distributor of other water filter media for industrial and commercial water filtration systems.
These are the various types of other water filtration media stocked by Express Drainage Solutions Kenya Limited:
- Activated Carbon filters- Activated carbon filters are generally employed in the process of removing organic compounds and/or extracting free chlorine from water, thereby making the water suitable for discharge or use in manufacturing processes. Eliminating organics in potable water, such as humic and fulvic acid, prevents chlorine in the water from chemically reacting with the acids and forming trihalomethanes, a class of known carcinogens. Activated Carbon (AC) filtration, as with any water treatment method, is not capable of removing every possible type of contaminant.
- Anthracite Filter Coal – Commonly used as sub-fill and as a component of multi-media filters, anthracite is a durable media with long life and a wide temperature range. It contains no silica to interfere in the production of ultra pure water.
- Garnet – At 126 pounds per cubic foot garnet is typically used in multi-media filters as the sub-fill or bottom layers of the filter. Although its density requires high backwash rates combining fine mesh garnet with other media such as sand and anthracite significantly increases the filtration capacity of a system.
- Filter Lite is a low-density media typically used in multi-media filters to enhance the capacity of the filter to remove smaller micron particles. At 24 pounds per cubic foot it sits as the top layer in a multi-media filter.
- MnO2 is a granular manganese dioxide media used primarily in potable water residential applications for the removal of hydrogen sulfide, iron and manganese. Chlorine is often used during regeneration cycle to ensure full capacity.
- Manganese Greensand is a dense media at 85 pounds per cubic foot. In addition to its filtration properties is can remove soluble iron, manganese and hydrogen sulfide from well water supplies.
- Greensand Plus – The second generation of greensand, this media is more rugged than the original but has identical operating characteristics. GreensandPlus is a purple-charcoal filter media used for removing soluble iron, manganese, hydrogen sulfide, arsenic and radium from well water supplies.
- Redox alloy is used for the efficient removal of chlorine and mercury remediation. It is universally applied from the smallest of water filters to large municipal and industrial equipment. It can also remove iron, hydrogen sulfide and chloramines.
- Neutralizing Media – Calcium Carbonate is commonly used to raise pH in residential well water supplies. To enhance the neutralization process the addition of magnesium oxide may be required.
What is sand sieve analysis?
- In Express Drainage Solutions Kenya Limited, sieve analysis (or gradation test) is a practice or procedure used (commonly used in civil engineering) to assess the particle size distribution (also called gradation) of a granular material. Express Drainage Solutions Kenya Limited collaborate with other relevant authorities to ensure we supply the best water filter media sizes.
- The size distribution is often of critical importance to the way the material performs in use.
Why sand sieve analysis?
- Express Drainage Solutions Kenya LimitedSieve analyses determine the gradation or distribution of aggregate particles within a given sample in order to determine compliance with design and production standards.
- The amount of material passing this sieve is determined by comparing dry sample masses before and after the washing process. This uses various sieves and a weighing scale to determine the weights of those which have passed and those which have been retained.
Why filter media size is important
- Mechanical filtration mechanisms; A slight increase in treatment efficiency has been observed with decreasing sand size which, indicates the importance of straining and adsorption. Higher removals tend to be due to smaller interstices (spaces) between smaller sand, as well as the larger surface area available of the smaller sand size, which allows more adsorption to take place. In the same way, having sand that is too fine will lead to rapid clogging.
- Cleaning; In coarser sand with a proportionally higher flow rate solids in the raw water are able to penetrate deeper into the sand making cleaning more difficult.
- Biological filtration mechanisms; A smaller size of sand will have a larger total surface area available for biofilms to grow on, and therefore more biofilm can come into contact with the raw water. This therefore improves treatment effectiveness.
How are the results of a sieve analysis expressed?
- Effective Size
- Uniformity Co-efficient
The results are plotted in a blank sieve analysis form as illustrated by the blank form below;
- The picture below illustrates Express Drainage Solutions, Kenya Limited staff and Donors demonstrating and constructing a model Water filtration tank for a county Government in KenyaAs the process itself, the Express Drainage Solutions, Kenya Limited basic structure is very elementary. Essentially, only the filter chamber, a type of reservoir and pipes are required. The filter chamber can be constructed using concrete stones or quarry silver stones with ferro-cement and water sealing cement for the joinery work. This process is illustrated by the drawing below.
- Once an Express Drainage Solutions, Kenya Limited Slow Sand Filter (SSF) facility is built, only clean sand is required for occasional replacement. The sand layers are put in gradually according to their grain sizes: rather coarse grains at the bottom and fine grains at the top. The sand-bed is usually covered with one meter of supernatant In order to make sure this slow sand water filter media work, there is a need to do a sieve analysis of the sand which is explained in the subsequent sections.
- Express Drainage Solutions, Kenya Limited slow sand filters differ from all other filters used to treat drinking water in that they work by using a complex biological film that grows naturally on the surface of the sand. The sand itself does not perform any filtration function but simply acts as a substrate, unlike its counterparts for UV and pressurized treatments.
- Although Express Drainage Solutions, Kenya Limited are often the preferred technology in many developing countries because of their low energy requirements and robust performance. Express Drainage Solutions, Kenya Limited slow sand filters now are also being tested for pathogen control of nutrient solutions in hydroponic systems.How does water filter media tank work?
- One strategy that is frequently employed to remove solids is gravity filtration (Figure above). In this process, water containing solid impurities (g., precipitates from water softening) is passed through a porous medium, typically layers of sand and gravel. The force of gravity is used to push the water through the medium. The small water molecules pass through the holes between sand and gravel pieces. However, the solids (from precipitation) get stuck in the holes, and are thus retained in the porous medium. The water that passes through the bottom of the filter no longer contains those solid impurities.
- Gravity filters at water-treatment plants have a pipe feeding into the under drain, the bottom layer where the clean water is collected. By adding water to the filter through this pipe, clean water can be forced upward through the filter to remove the solids that have collected in the filter. This process is used to clean the filter and is called backwashing.
- The basic principle of the process is very simple. Contaminated freshwater flows through a layer of sand, where it not only gets physically filtered but biologically treated. Hereby, both sediments and pathogens are removed. This process is based on the ability of organisms to remove pathogens. In this context, it is important to distinguish slow and rapid sand filtration. The difference between the two is not simply a matter of the filtration speed, but of the underlying concept of the treatment process. Slow sand filtration is essentially a biological process whereas rapid sand filtration is a physical treatment process. To learn more about rapid sand filtration have a look at the factsheet: rapid sand filtration.
- Although the physical removal of sediments is an important part of the purification process, the relevant aspect is the biological filtration. The top layers of the sand become biologically active by the establishment of a microbial community on the top layer of the sand substrate, also referred to as ‘schmutzdecke’. These microbes usually come from the source water and establish a community within a matter of a few days. The fine sand and slow filtration rate facilitate the establishment of this microbial community. The majority of the communities are predatory bacteria that feed on water-borne microbes passing through the filter. Hence, the underlying principle of the SSF is equivalent to the bio-sand filtration. While the former is applied to semi-centralized water treatment, the latter mainly serves household purpose
Express Drainage Solutions Kenya Limited can supply water filter tank nozzles as illustrated below;
Express Drainage Solutions Kenya Limited is capable of supplying even designer or tailor made nozzles at very short notice. Give us a buzz! We can advise on and supply the following types of nozzles illustrated in the page overleaf;
The picture below illustrates how Express Drainage Solutions Kenya Limited carry out backwashing/maintenance of water filter media tank. Each arrow in the tank indicates the multiplicity of purpose of the various parts of the water filter media tank;
In terms of water treatment, including water purification and sewage treatment, backwashing is a form of preventive maintenance so that the filter media can be reused.