Rotary Press – Innovative New Technology for Dewatering Municipal Biosolids A Case Study of Hampton, New Hampshire

The purpose of this paper is to introduce the municipal wastewater community to a largely undiscovered piece of biosolids dewatering equipment called the rotary press. This will be introduced largely through a case study of the Hampton, New Hampshire municipal wastewater treatment facility installation. It is one of two municipal installations of this technology in the United States. The rotary press was developed by an agency of the Canadian Government (Quebec Industrial Research Center) and commercialized by Fournier Industries of Blake Lake, Quebec, Canada. The dewatering process involves feeding sludge into a series of circular channels where the sludge is sandwiched between two, low-speed (0.3 to 4 RPM), rotating perforated screens. With a pneumatically controlled adjustable discharge wedge to maintain backpressure, filtrate passes through the screens while flocculated sludge remains and advances within the channel, eventually forming a cake near the outlet of the press.The most common means of dewatering municipal biosolids currently employed throughout our industry are belt filter presses and centrifuges. Through pilot testing, along with the full-scale installation at Hampton, New Hampshire, the rotary press has demonstrated worthiness as a viable option to the tried and true belt filter presses and centrifuges. The benefits include increased cake solids, lower biosolid disposal costs, reduced operation and maintenance costs, reduced footprint, and simplified odor control and containment of potentially harmful aerosols due to their compact fully enclosed design. Other inherent advantages include its slow rotational speed with less noise, vibration and wear, and reduced corrosion potential.