Why Well Water Needs Different Treatment Than Municipal Water
Municipal water in Bangladesh, despite its imperfections, goes through some level of treatment before reaching your tap β typically chlorination to address microbial contamination. Well and borehole water receives no treatment at all. It arrives at your tap exactly as it exists in the ground: with whatever minerals, bacteria, chemicals and contaminants are present in your local geology and surrounding environment.
This does not mean well water is unsafe β in some areas, deep borehole water is exceptionally pure. But it does mean you cannot assume it is safe without testing. The contamination profile of well water is also completely different from municipal water, and choosing the right purifier requires understanding that difference.
The Four Main Risks in Well and Borehole Water
Risk 1 β Arsenic (Shallow Wells, Central and Southern Bangladesh)
Shallow tubewells (typically 20β80 metres depth) in the alluvial plains of Bangladesh frequently tap into arsenic-rich geological layers. As described in detail in our arsenic guide, tens of millions of people are exposed. Deep aquifers (150+ metres) generally have lower arsenic levels, but this varies significantly by location.
Test for: Arsenic using field test kit or laboratory analysis. A TDS meter will not detect arsenic.
Risk 2 β Microbial Contamination (All Shallow Wells)
Shallow wells are vulnerable to faecal contamination from nearby latrines, agriculture runoff, and flood events. Bacterial contamination (E. coli, coliforms) causes acute gastrointestinal illness and is the leading cause of waterborne disease from well water in Bangladesh.
Contamination risk increases significantly:
- When the well casing or seal is damaged or cracked
- After flooding or monsoon events
- When the well is within 10 metres of a latrine or septic system
- In densely populated areas with poor sanitation
Test for: E. coli and total coliforms. Field test kits are available; laboratory testing is more reliable.
Risk 3 β Iron and Manganese (Many Regions)
Elevated iron and manganese are extremely common in Bangladesh groundwater, particularly in Sylhet, Chittagong, Rajshahi, and many parts of Dhaka division. Signs of iron contamination are visible:
- Reddish-brown or orange colour in water (especially after standing)
- Rusty stains on sinks, toilets, clothes and fixtures
- Metallic taste
- Black stains (manganese)
High iron does not present the same acute health risks as arsenic or bacteria, but it damages appliances, stains everything it contacts, and makes water unpleasant to drink. It also clogs RO membranes and other purification equipment rapidly.
Treatment: An iron removal filter (oxidation and sedimentation, or birm/manganese greensand media) must be installed before your primary purification system.
Risk 4 β High TDS and Hardness (Coastal and Some Inland Areas)
Groundwater in coastal districts has elevated salinity from seawater intrusion. In other areas, geological dissolution of calcium and magnesium creates very hard water with high TDS. TDS above 500 ppm causes scaling, appliance damage, and in the case of coastal saline intrusion, genuinely unpleasant and unsuitable drinking water.
How to Test Your Well Water: Step by Step
Step 1 β Basic Tests You Can Do Yourself
| Test | Tool | What It Tells You | Cost |
|---|---|---|---|
| TDS | Digital TDS meter | Total dissolved solids level | ৳300β৳500 |
| pH | pH meter or test strips | Acidity/alkalinity | ৳200β৳600 |
| Iron (visual) | Fill white container, let stand | Orange tint = iron present | Free |
| Odour | Smell the water | Rotten egg = HβS; chlorine = disinfection | Free |
| Turbidity | Visual | Cloudiness = suspended particles | Free |
Step 2 β Field Test Kits
Arsenic field test kits and basic coliform test kits are available from water supply NGOs, DPHE offices, and some pharmacies in affected areas. Field kits are not as accurate as laboratory tests but are immediate and low cost.
Step 3 β Laboratory Testing
For comprehensive well water analysis, submit a sample to an accredited laboratory. Collect the sample in a clean, sterile container (lab will provide). Test for: TDS, pH, arsenic, iron, manganese, nitrate, E. coli, and total coliforms. Full panel cost: ৳2,000β৳5,000. Results typically in 3β7 days.
Key sampling rule: Run the well pump for 5β10 minutes before collecting the sample to flush standing water from the pipes and get a representative aquifer sample.
Treatment Matching Your Well Water Test Results
| Test Result | Required Treatment |
|---|---|
| High arsenic (above 10 Β΅g/L) | RO purifier rated for arsenic removal |
| E. coli / bacterial contamination | UV purifier or boiling (plus address contamination source) |
| High iron (above 0.3 mg/L) | Iron removal pre-filter before any other purification |
| High TDS (above 500 ppm) | RO purifier |
| High TDS + arsenic + bacteria | Multi-stage: Iron filter β Sediment β Carbon β RO β UV |
| Low TDS + bacterial risk only | UV or ceramic filter (no RO needed) |
| High turbidity | Sediment pre-filter (multiple stages if very turbid) |
Special Consideration: Deep vs Shallow Wells
Shallow wells (less than 30 metres): Highest risk for bacterial contamination and arsenic in affected areas. Treat as high-risk until tested.
Medium depth (30β100 metres): In many arsenic-affected areas, this is the highest-risk zone for arsenic. Often incorrectly assumed to be safe because it is deeper.
Deep wells (150+ metres): Generally lower arsenic risk in most areas, though this varies. Still requires testing β deep aquifers can have other mineral issues including elevated fluoride in some regions.
BRAC and DPHE colour-coding: In many villages, tubewells have been tested and painted red (unsafe β arsenic above 50 Β΅g/L) or green (safe β below 50 Β΅g/L). However, these tests may be years old and conditions change. Treat a green-coded well as safe for now but retest if circumstances change (new industrial activity, land use changes, flooding).
After Installing a Purifier: Ongoing Well Maintenance
Installing a purifier does not remove the need to maintain the well itself:
- Inspect the well casing and seal annually for cracks or damage
- Ensure the area within 10 metres of the well head is kept free of latrines, animal pens and waste
- After any flood event, have the well tested before resuming use β even if it was safe before
- Retest water annually β contamination levels in wells change with seasons, nearby land use and water table fluctuations
Your well is an asset that requires maintenance. Treat it alongside your purifier as a system β the best purifier cannot compensate for a grossly contaminated well that is recontaminating the source water continuously.