Anew ballasted biological treatment process has helped the Allenstown (N.H.) Wastewater Treatment Plant expand capacity in response to orders from state regulators who had placed a moratorium on new sewer hookups.The lower cost of the new process enabled the plant to make the improvements in the first place, since ratepayers had voted down previous bonding proposals to expand the facility. The new technology also allows the plant to achieve complete nitrification.The Allenstown facility serves two municipalities with a combined population of 15,000. The original plant was designed 30 years ago as an extended aeration activated sludge process with 1.05 mgd
