There are various contaminant types that can make surface water unsafe to drink and learning how best to reduce/remove these contaminants is critical to emergency water treatment.
These contaminants can generally be classified as particulate, biologic and chemical substances.
In this part of this water treatment tutorial we will focus on particulate.
Particulate contaminants in water can be divided into two types characterized by passing the water through a fine filter (1.5 microns). The particles that are large enough to be held back by the filter are called total suspended solids (TSS), while the particles that pass through the filter are called total dissolved solids (TDS).
Suspended particulates that make the water cloudy include sediments such as silts and clay, and fine inorganic or organic matter such as algae. The technical term for this cloudiness is called “turbidity”. Water turbidity is measured by determining the clarity or transparency of a water column.
One simple instrument to measure turbidity is clear cylinder (usually 1 meter tall and 2 inches in diameter) that has a target design on the bottom. The cylinder is filled with water and slowly released from the bottom until the target becomes visible when looking down from the top of the tube. The tube has a side scale with Nephelometric Turbidity (NTU) unit’s markings on the side (0 to 60 NTU scale). Water suitable for drinking should read close to 0, meaning the target is visible through a full-length column of water.
High turbidity in water can cause several water treatment and human health concerns. These include:
And
For these reasons, it is best practice to remove/reduce the particulate loading of your water source before filtering though your PortaWell (or any filter for that matter). Even using a 1-micron prefilter may not be enough to reduce the particulate load enough to substantially extend the life of your micro filter. This is because the inexpensive prefilter has a nominal rating meaning the only 60 to 80 percent of the particles sized 1-micron and greater are captured. The remaining particles can pass through the prefilter and prematurely clog the more expensive micro filter. The micro filter has an absolute rating meaning that greater than 99.9 percent of the particles greater than the filter pore size are captured.
There are several ways to reduce the water turbidity but first aways choose the cleanest water source possible with the least amount of cloudiness to minimize the particulate loading in the water.
For water with visible turbidity and before filtering through PortaWell
This consists of adding a small amount (1/4 tsp to 5 gallons of water) of an inert chemical to the water and stirring vigorously for a short time. After waiting for a period of time, this causes the fine particles to clump together into a substance called floc that more quickly separates from the liquid water. One common chemical used as a flocculant additive is alum which can be purchased from the spice aisle of your local grocery store.Dissolved solids in water include salt (i.e. sea water, brackish water, saltwater swimming pool) and minerals such as magnesium and calcium. While high salt (sodium chloride) levels (above 250 ppm) make the water unsuitable for human consumption, minerals like magnesium and calcium that make the water “hard” are essential to human health It is this reason some avoid reverse osmosis (RO) treated water, because it removes these trace minerals. Even some bottled water brands will reintroduce these minerals after the water has been RO treated. High levels of these dissolved solids ( > 1000 ppm) can affect the taste and may have some unpleasant gastrointestinal side effects such as diarrhea, but they are generally not considered harmful to human health.
Dissolved Solids cannot be removed via ordinary filtration but must use processes such as reverse osmosis filtration, distillation, or ion-exchange.
A simple TDS meter can be purchased for less than $30 US and can measure the dissolved solids level of a water sample.
Pretreating water with high turbidity before you run it through your PortaWell filters can greatly extend the life of your filters. In an extreme situation where you may have to rely on your PortaWell (or any filtration system) to provide safe drinking water for a lengthy period, it is important to make your consumables (filters) last until the emergency is over.
The pre-treatment processes described above are like those used by your municipal water treatment plant but on a much smaller scale. It is important to not only have the proper equipment to provide clean and safe drinking water, but also to know what your potential surface water sources are and how to configure your PortaWell for efficient and safe use.
Next we will cover biological contaminants, what they are and how best to reduce/remove them.
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