Application of controlled nutrient release to permeable reactive barriers

• Timeframes of nutrient release from two controlled release fertilisers is examined.
• Increasing temperature shortened timeframes of controlled nutrient release.
• Activated carbon rapidly depleted nutrients from nutrient amended zeolites.
• Increasing flow velocity was shown to alter nutrient release rates.
• Nutrient release was shown to be unchanged in the presence of petroleum hydrocarbons.

The application of controlled release nutrient (CRN) materials to permeable reactive barriers to promote biodegradation of petroleum hydrocarbons in groundwater was investigated. The longevity of release, influence of flow velocity and petroleum hydrocarbon concentration on nutrient release was assessed using soluble and ion exchange CRN materials; namely Polyon™ and Zeopro™. Both CRN materials, assessed at 4 °C and 23 °C, demonstrated continuing release of nitrogen, phosphorus and potassium (N–P–K) at 3500 bed volumes passing, with longer timeframes of N–P–K release at 4 °C. Zeopro™–activated carbon mixtures demonstrated depletion of N–P–K prior to 3500 bed volumes passing. Increased flow velocity was shown to lower nutrient concentrations in Polyon™ flow cells while nutrient release from Zeopro™ was largely unchanged. The presence of petroleum hydrocarbons, at 1.08 mmol/L and 3.25 mmol/L toluene, were not shown to alter nutrient release from Polyon™ and Zeopro™ across 14 days. These findings suggest that Polyon™ and Zeopro™ may be suitable CRN materials for application to PRBs in low nutrient environments.