BiologicalNutrient Removal Plants:

Reviewof Full-Scale Operation

ReportNo WSAA 94

May 1995




Biologicalnutrient removal (BNR) is a relatively new technology and only a limited numberof full-scale plants are operating in Australia. The aim of this study was toreview the operating experience at the first seven Australian BNR plants (allcontinuous flow format) and four intermittent process plants in the USA. Theseplants were located at Albury, Ballarat, Bendigo, Brendale, Penrith, South Windsorand West Wodonga in Australia, and Flushing, Dundee, Catawba and Foxwood in theUSA.


Eachof the Australian plants was visited for discussion with operators andcollection of data. Daily operating data for the 1993 year were then analysedin detail. Information on the US plants was supplied by US consultant CH2MHill.


Biologicalphosphorus removal capacity was found to be fairly consistent between plantsand averaged about 0.017 times biodegradable COD in the wastewater, decliningslightly as feed TKN/COD ratio increased. Of the intermittent plants, data fromonly one was useful in this evaluation and performance of that plant wascomparable with the continuous flow plants.


Effluentvariability was high. Geometric standard deviation for effluent qualityparameters averaged: COD or BOD 1.7, SS 2.0, total P 2.0, total N 1.7, NH3-N2.9.


RBCODdata measured by aerobic batch test method were available for three plants.Phosphorus removals calculated from these RCOD concentrations using the UCTmodel were consistent with plant performance. At three plants, short sludge ageprefermentation appeared to enhance phosphorus removal to a limited degree.


Guidelineswere developed for operational, staffing and cost parameters. Capital cost ofexisting BNR plants was more sensitive to effluent phosphorus concentrationthan nitrogen concentration. Cost of a new BNR plant was 30% higher than asecondary treatment plant at mean effluent phosphorus of 2 mg/L and at lowerconcentrations was inversely proportional to the 0.5 power of the meanphosphorus concentration.


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