- Nitrate can enter groundwater and surface water from agricultural and sewage-related sources.
- DWI guidance states that water above 50 mg/L nitrate should not be regularly consumed.
- A high result needs local-authority assessment in the context of source-to-tap risk.
- Treatment can include specialist ion exchange or membrane processes, but source control and trend data also matter.
Where nitrate comes from
DWI lists fertilisers, animal wastes and sewage effluents as common nitrate sources. Groundwater catchments can show persistent or seasonal trends depending on land use and recharge.
Why a single result needs context
A laboratory result is important, but DWI guidance asks local authorities to consider historic minimum, maximum and average concentrations, trends, future source risk and how the water is used.
The 50 mg/L standard
DWI states that UK health advice does not recommend anyone regularly consuming drinking water above 50 mg/L nitrate. A result above 50 mg/L exceeds the drinking-water standard and should be handled through the local authority and appropriate health guidance rather than self-managed from an internet article.
Treatment options
DWI treatment guidance identifies specialist processes such as ion exchange and membranes for nitrate removal. Treatment selection depends on water chemistry, flow, waste handling and competent design.
Operational evidence
Keep the original laboratory report, sample point, historical trend, catchment notes, treatment service history and any alternative-water or corrective-action records together.
Practical checklist
- Preserve the original nitrate result and units.
- Review older nitrate results for trend.
- Record relevant catchment/land-use changes.
- Follow local-authority advice on immediate measures.
- Keep treatment design and maintenance evidence.
Frequently asked questions
Is 50 mg/L the nitrate standard?
DWI guidance refers to 50 mg/L as the drinking-water standard and states that regular consumption above this concentration is not recommended.
Will a carbon filter remove nitrate?
Standard activated carbon is not the normal nitrate-removal process. DWI treatment guidance points to specialist methods such as ion exchange or membranes.
Keep the records behind this work together.
Use the free tools or start a 7-day trial to see how sampling, maintenance, actions and documents can sit in one source-to-tap record.
- DWI: Nitrate and private water supplies
- DWI: Common contaminants and their sources
- DWI: Chemical removal of contaminants
Regulatory guidance can change. Check the current DWI material and your local authority for the position applying to your supply.