How sand and stones help in water purification especially in areas with oil contaminated waters

Water is a fundamental requirement for survival and smooth running of our day to day activities and it’s not surprising how the total earth mass involves about 70% water, The earth itself shows the necessity and importance but the painful part is when this necessity becomes a burden.

How’s this possible you may ask?

Well, when water lack the necessary component of importance or it contains foreign components harmful to man, it can become a burden.
Normally water is composed of two elements; Hydrogen and oxygen but oil spillage alters this composition making water to contain foreign and harmful compounds like hydrocarbons such as toluene, benzene and oxygenated polycyclic aromatic compounds. The downside to this is in the up rise of health complications like skin irritations, respiratory damage, increased cancer risk, liver damage amongst others.

Lately, I’ve been curious about a lot of things and my mind wandered into the water purification system of where I currently resided.

Let's discuss Sand fitration

Moving to Bayelsa{Due to my 1 year compulsory service(NYSC)} located at the South-South geo-political zone of Nigeria, I experienced a big shock😲when I discovered from the residents that the water was contaminated with Crude oil( Bayelsa is a Nigerian State know for its vast availability of crude oil and petroleum materials, it is also the 4th largest Oil producing States in Nigeria) I didn’t know how I would survive that but amazingly I met clean water at my place of residence more often than I saw contaminated water and the question on my mind was how did they do it?

After much research I realized they used a process called Sedimentation/ Sand filtration. This process involves the use of sand, stones and other materials to be able to get clean, clear and fairly decontaminated water.
How is this possible you may ask? Let me hold your hands as we discover this together😁...

Majority of the residence due to the high cost of modern techniques to decontaminate water use a fairly expensive method know as Sedimentation-filtration method. This method involves to use of materials such as Sand, activated charcoal, pebbles and stones to serve as filtration materials and how it is done is shown below.

Using the image above, The middle tank contains sand and stones in different layers, The bottom layer(fifth layer) is filled with sand(like the texture of beach sand), above it(fourth layer)is filled with activated Charcoal, the third layer consists of small pebbles/granites, after which pebbles slightly bigger than those in the third layer is added in the second layer, finally the top(first layer)is filled with large stones.

Contaminated water(directly from the ground) is pumped into the tank through the pipe at the top of the middle tank.
The water flowing from the ground enters into the tank and lands on the first layer(large stones) where the filtration process begins.

The water passes through the bigger stones, so bigger sediments and impurities are trapped here and these impurities include tiny fossils mostly, Afterwards, it passes through the smaller ones which traps smaller sediments that could escape the bigger stone layers, this water then passes through the activated charcoal which serves as an adsorbent that purifies the water by trapping microorganisms and also good for trapping carbon-based or hydrocarbon impurities before it gets to the sand and final layer.

Due to the size and quantity of sand in this layer, there is no source of food and air for microorganisms to survive thereby trapping the colouration by the oil and microorganisms so when it makes its way to the tank below, the water appears clear. Further purification like addition of chemicals is introduced to get rid of pathogens that survived the whole purification process.

The middle tank that has been identified so far is called settling or sedimentation tank which allows suspended particles to settle out of water or gather contaminants at a spot allowing the flow of fairly decontaminated water out for usage.

A-Middle tank
B-Pipe connecting middle tank to the pumping machine
C-Control switch(to turn on and off the water supply from the pumping machine)
D-Pipe linking the water supply from the pumping machine to the down tank and middle tank.
E-Pumping Machine
F-Down tank
G1 and G2- Pipe connecting the bottom of the middle tank to the top of the down tank.
F-Control switch to allow or stop the water supply to the middle and down tank.

The diagram above is a sketch of the filtration system and pattern used in Bayelsa.

This process has its perks. Asides being inexpensive, it is environmental friendly as all the materials used have little or no adverse effect to the health and the environment at large, Activated charcoal used is beneficial in skin care routine serving as an exfoliant and being available in a certain proportion in the water can serve this purpose. Saying this based on experience, I realised that despite the irritation as a result of change in environment and the water my body is used to, my skin (face to be precise) became some what acne free.

Let's consider that this may not apply to everyone, the harsh condition of the water may bring about certain allergies to people like itching, skin colour alteration, etc. Places where proper filtration of the water is not taken note of can make the reaction a bit more severe. Oral use of the water could also cause itching in the throat, a slight distaste when water is not properly filtered. So it is advisable to boil the water thoroughly and add chemicals like alum before oral usage.

Despite this method having so many positive review, extra efforts can be introduced to make it almost 100% reliable. To do this Chemicals that help in phosphate removal, pH adjustment, removal of excess chlorine that can cause a distaste and cleanliness in general must be used to avoid certain discomfort or health issues that may arise.

There you have it, Hope this discovery was insightful, let me know what you feel about it in the comment section.

All images taken by me.

REFERENCES

https://en.m.wikipedia.org/wiki/Oil_spill
https://sswm.info/sswm-university-course/module-6-disaster-situations-planning-and-preparedness/further-resources-0/slow-sand-filtration
https://wikiwater.fr/a23-sand-filtration-for-raw-water
https://www.sciencedirect.com/topics/engineering/sand-filter
https://royalbrinkman.com/knowledge-center/technical-projects/water-filter-technologies-horticulture/sand-filter