Rain and Borehole Water Filtration Solutions

November 25, 2020

Water filtration has become a popular interest amongst South Africans, especially due to the water crisis a couple of years ago - which is now affecting Port Elizabeth.

Rainwater purification

Rainwater is generally pure if you already have a pre-filtration system in place (a leaf catcher, first flush diverter etc). However, if it's for your home, and mainly to drink the water, you would want to run some kind of filtration.

Borehole & water filtration solutions

A favoured unit for rainwater harvesting is the 3 stage Big Blue water filtration system, coupled with a 55W UV sterilizer, which can manage +/- 2700 litres of water per hour. The sediment filter removes all sediment, such as sand, dust, algae, rust, mud, slime and gecko egg shells, from your water down to 1 micron. The carbon block filter removes pesticides, chlorine, volatile organic compounds, and improves the taste, colour and odour of your water. The UV sterilizer ensures that when the water goes through the chamber, it doesn't cast any shadows over what potential bacteria or viruses could be in there. The UV sterilzier effectively neutralizes the bacteria in your water and makes it safe to drink.

What is borehole water filtration?

Drilling a borehole is another well-known way to secure access to water. The process is to drill a hole into the ground until the water table is reached. It can be as shallow as 8m or as deep as 200m. The next step is to install a pump that sits in the water table and brings the ground water up, which will then go into your reservoir.

The first thing that you need to do when it comes to filtering borehole water, is to get your water tested. This sort of gives you an x-ray of what your water looks like, and determines what you will need to treat it. Water tests should be done every 6 months to a year, due to heavy rain falls.

Post treatment water analysis
Post treatment water analysis example

What can you expect to find in the water?

There are four common problems that can be found in borehole water:
  1. Water turbidity - this is caused by suspended solids, causes your water to be murky, quite easy to identify
  2. Dissolved solids/metals (iron and manganese) - this is what causes the brown staining on your walls
  3. Hard water (elevated levels of calcium and magnesium) - this causes scale. You get scale on kettles, irons, geyser elements, this reduces the efficiency of these appliances
  4. Bacteria (such as e.Coli) - these pathogens can cause serious health risks

Solutions for common borehole water filtration problems:

How to treat water turbidity:

Water turbidity causes your water to become murky, if there is a lot of sediment in the water. If there is little, you may see it in the filter but not in your water. A new technology on the market, AFM (activated filter media), replaces the old technology, which is sand filters (commonly used for pool water filtration). The problem with this sort of filtration is that it only filters down to about 40 micron, and needs to be replaced every 3 - 4 years. It also has the potential to build up bacteria, if the water isn't constantly running through it.

AFM filter media

AFM® Activated Filter Media, NSF Certified, 2 - 4mm (Grade 3), 25kg

The AFM, glass media, comes in 4 grades and it can filter down to about 5 micron. It lasts up to 15 years, hardly needs to be replaced, making it cost-effective in the long run.

The filter media gets placed in a FRP (fiber-glass reinforced) vessel, which can manage up to 10 bar operating pressure, and is very robust. Depending on the size of the filter is determined on what your requirements are (how much water do you need; have you got a 5-person household or a 2-person household).

There is a pipe that runs down the center of the vessel, and at the top and bottom of the pipe are little strainers that will prevent the media from actually entering the water line and coming through your taps, or showers.

The automatic backwash head can be set to run a backwash every 3 days, for 15 minutes, at a time that you know will not interrupt your water supply. When it runs a backwash, it reverses the cycle and agitates the media, removing all of the sediment and particles it has caught, and backwashes it out, cleaning your filter.

How to treat dissolved solids:

Other common contaminants are iron and manganese, these can cause major issues with your laundry - turning your whites to browns. Katalox, an advanced removal filtration media, can be used to treat dissolved iron.

Katalox Light® Iron, Manganese & Hydrogen Sulfide Removal Filter Media, NSF Certified, 30kg
Katalox Light® Iron, Manganese & Hydrogen Sulfide Removal Filter Media

If you're using the water to fill up your pool, keep in mind that chlorine oxidizes iron and manganese, and you will end up with iron and manganese sitting at the bottom of your pool (you may need to empty your entire pool if this occurs!). The tricky thing about iron is that the water can actually appear clean, but only once it is exposed to oxygen and oxidized, then it comes out of solution and causes the brown stains.

How to treat hard water:

Hard water is essentially elevated levels of trace minerals - calcium and magnesium. Together, they are called calcium carbonate. Here we would recommend a softening resin, Polymex. It attracts the calcium and magnesium particles to the media, which leads to an actual salt water regeneration (iron exchange process) where it exchanges particles with sodium, flushes out the calcium and magnesium, and gives you clean media.

Polymex Softening Resin Media, NSF Certified, 25Lr
Polymex Softening Resin Media, NSF Certified, 25Lr

How to treat bacteria:

There are two ways to treat bacteria: One is to use a UV sterilizer, which disinfects the water by neutralizing it from harmful bacteria, protozoa and spores. If you want to be super precautious, and if you have high levels of E.coli, we recommend using an inline chlorinator. This introduces a bit of chlorine into the line, that will take care of the bugs and bacteria for you. You can also remove the chlorine with a carbon filter.

55W UV sterilizer and inline chlorinator

55W UV Sterilizer Complete Set, 960mm, 2700 LPHKLORMAN Inline Chlorine Feeder Unit

What are the costs & factors of treating your borehole water?

There are always ways to bring the costs down - but there are some factors that you cannot avoid if you want your water to be potable or drinkable. Instead of having an automatic backwash, you could opt for a manual backwash head. Generally if you are plumbing it into your whole house, you are going to have a higher flow rate requirement, therefore a bigger FRP vessel is needed, and with a bigger vessel - more filter media will be needed.


What is the process of treating borehole water?

The first step to treat your borehole water is to get your water tested. Once it is tested, you can send the information to info@ecodepot.co.za. We will then study the water test results and ask you a couple of questions, before we propose a system that will work for you.


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