Grey water treatment through biofilm development and sediment accumulation in a horizontal batch-operated open reactor
To upgrade grey water for higher-purpose reuse in decentralized systems, simple process unit operations for mineralization of bulk organic matter and removal of non- or slowly degradable particles are required. We conducted two 16-day experiments on light grey water, using a shallow, open to the air reactor of 2 m × 0.6 m × 0.05 m, equipped with a 0.05 m thick polyamide net to support passively aerated biofilm, and applying a gravity-driven batch flow-mode at 1.44 m3/day, first with full drainage of each batch (60 L), then with only half drainage (30 L), leaving a stagnant water layer behind. Turbidity, chemical oxygen demand and total suspended solids were significantly reduced in both experiments, documenting the passive aeration to be efficient, and some sedimentation to take place. Despite 50% shorter hydraulic residence time, the biofilm developed faster and was better distributed in the half drainage experiment, endorsing this principle.