A solids dewatering system designed for facilities producing less than 250 pounds of dry solids per day may provide a solids management solution for smaller municipalities. The system collects biosolids in porous polyethylene bags and stabilizes the solids through gravity and pressurization.
After only a few hours of operation, the Draimad system from Aero-Mod Systems can achieve a dry solids content of 10 to 12 percent. The bags can be stacked outdoors for up to two years for further drying and solids contents of up to 90 percent.
The key to the Draimad system is the porous, disposable polypropylene bags used to store the sludge. The material allows air to enter for natural drying, yet repels most rainwater, making it possible to dewater during winter.
During operation, a facilitys sludge stream is combined with a conditioning polymer that aids in liquid and solids separation. The mixture is flocculated and injected into an enclosed hood which funnels the conditioned sludge into the suspended bags. The bags allow free water to drain out, retaining the solids.
Models are available with three, six or 12 bags, depending on flow rate. Multiple units may be installed either in series or parallel. The Draimad system is also portable and can be mounted on a trailer to dewater at more than one facility.
After the initial dewatering stage on the machine, the bags are removed with a special bag trolley and stored in the open. During the draining phase, sludge weight and volume continue to reduce. Following two months of storage, a biosolids content of 50 percent to 90 percent dry solids can be produced.
For example, 1 cubic meter of sludge at 1 percent solids content would have a solids content of 10 to 12 percent solids after a few hours of resting in the bags. After two months, the content would be around 50 percent and the bag would weight only 44 pounds.
The Draimads sludge pumping and conditioning system consists of a progressive cavity sludge pump, either a liquid polymer mix/feed system or a batch system, an internal static flocculator for the sludge/polymer mixture and electrical controls for automatic operation.
Installation typically requires plugging into a 115 volt receptacle, installing a 2 inch pipe to the sludge tank, and connecting to a drain and water supply.
To minimize operator attention, timers and level sensors control system operation. This allows for dewatering on a uniform schedule, reducing the potential for plant upsets caused by irregular wasting and increased solids accumulation. One button starting and straightforward maintenance add to the convenience of the system.
Features common to all Draimad systems include a pressurized hood, collars, clamps and stainless steel bag cases, a drainage collection tray beneath the machine, an internal sludge distribution system, and a specially designed bag trolley for handling the full bags.
According to Aero-Mod, there are more than 200 units in operation in Europe and the United States on many types of mixed sludges, including domestic wastewater sources and water plants. The system was developed by Teknofanghi of Milan, Italy, and is marketed exclusively by Aero-Mod in the United States.
