Cleaning Water: Making water safe at home, at work and in agriculture

Nitrates

Why is there nitrate in ground water?

The origin of nitrate in groundwater is primarily from fertilizers, septic systems, and manure storage or spreading operations. Fertilizer nitrogen not taken up by plants, volatilized, or carried away by surface runoff ends up in the groundwater in the form of nitrate.

Nitrate correction media

The most common method of removing nitrate is with an ion exchange resin. The nitrate rich water passes over a resin where the nitrate is exchanged for chloride ions. When no more nitrate can be exchanged the resin needs to be replaced or regenerated by rinsing with salt. Reverse Osmosis can also remove nitrate from water. The water passes through very small pores at a high pressure. This combination stops most contaminants just allowing water molecules through, however, RO systems are relatively expensive, may require the water to be pre-treated, and often remove beneficial minerals. They also give relatively low flow rates (litres/day).

How does it work?

The most common method of removing nitrate is with an ion exchange resin. The nitrate rich water passes down through a nitrate selective resin where the nitrate is held. When no more nitrate can be held the resin needs regenerating by backwashing with a concentrated solution of salt (brine). The resin bed is then rinsed with clean water and returned to service. The nitrate reduction resin is a food grade DWI approved resin for use in drinking water applications.

How to size

On average 160 litres of water is used per person per day. This normally occurs in two peak periods, one in the morning and one in the evening. A family of four typically uses 700 litres of water per day but may use 300 litres in an hour in the morning. Larger households, farms, stables and irrigations systems all use more water.

When sizing a system the average flow and the peak flow rate need to be taken into account. Try and size a system to run for 3 days without regenerating or a duplex for 12 hours. The vessel size is often given as the diameter and the height (in inches). Recommended operating pressure range 20 to 120 PSI. Water temperature ranges from 2 to 38°C