Complete the summary using NO MORE THAN ONE WORD for each answer.

Construction of a reed bed

• Rectangular hole 1 metre deep lined with [1]

• System of perforated tubing embedded in gravel

• [2] planted in bed

Process

• Sewage flows [4] from tank into reed bed.

• Oxygen from reeds combines with bacteria to reduce waste to elements.

• Water is [5] then released.