Guidelines for Wet Muck Out

THE WET MUCK OUT/HYBRID SYSTEM

iv) Aeration Tank

The main purpose of an aeration tank is to facilitate the biological treatment of wastewater by pumping or inducing air into it.

An aeration tank should be leak-proof, and sufficiently large to enable aeration to take place without overflowing. In general, there should be at least 0.285m³ of aeration tank volume per porker if a full wet muck out system is used. Less tank volume will be required for a hybrid system, depending on the effectiveness of the dry muck out operation.

There are many types of aeration systems using different types of aerators, with different design and operating requirements for the aeration tank. Aeration system suppliers should be able to recommend the most appropriate system for each individual farm and provide technical advice on the operation and maintenance aspects. A typical aeration tank comprises an aerator, a wastewater inlet, a treated water outlet and a sludge outlet. In general, wastewater should be continuously aerated so as to maintain a dissolved oxygen level of 1-2mg/L for 18 to 20 hours. This should be followed by at least an hour of settling in order to achieve the required quality for discharge. The settled sludge should be drained off to a drying unit after each aeration cycle. It must be stressed that excessive aeration could also result in very poor treated water quality. Farmers are therefore strongly advised to adhere strictly to the suppliers' operating recommendations and seek their assistance whenever necessary.