Nut shell filter

Typically nut shell filters are designed for loadings under 100 mg/L oil and 100 mg/L suspended solids and operate with 90–95% removal efficiency.

Although it is possible to use other medias for this purpose, walnut and pecan shells are most commonly used since they have several desirable properties making them well suited for oil removal.

First, nut shells are hard with a high modulus of elasticity, resulting in a low attrition rate and minimal media replacement, typically <5% per year.

[4] Commercial vessels are sized to accommodate the flow rate of water and range up to 14 feet in diameter.

Nut shell filters were designed to separate crude oil from oilfield produced water in the 1970s, which remains the principal use.