Impact of Media Type and Various Operating Parameters on Nitrification in Polishing Biological Aerated Filters

Abstract

Three biological aerated filters (BAFs) composed of a PVC pipe with a diameter of 75 mm were constructed and operated at a wastewater temperature at 13°C. The media used for each BAF were: 5-mm gravel; 5-mm lava rock; 12.5-mm diameter by 15-mm long plastic rings, all with a media depth of 1.7 m. The feedwater, which simulated the effluent of aerated lagoons, had influent soluble chemical oxygen demand (sCOD) and ammonia concentrations of approximately 50 and 25 mg/L, respectively. For a hydraulic retention time (HRT) of two hours without recirculation, ammonia percent removals were 98.5, 98.9, and 97.8%, for the gravel, lava rock, and plastic rings, respectively. By increasing the effluent recirculation from 100 to 200% for an HRT of one hour, respective ammonia removals improved from 90.1 to 96, 76.5 to 90, and 65.3 to 79.5% for gravel, lava rock, and plastic rings. Based on the ammonia and sCOD loadings for different HRTs, the estimated maximum ammonia loading was approximately 0.6 kg NH 3 -N/m 3 -day for the three BAFs of different media types. The zero-order biotransformation rates for the BAF with gravel were found to be higher than the lava rock and plastic ring media. The results ultimately showed that BAF can be used as an add-on system to aerated lagoons or as a secondary treatment unit to meet ammonia discharge limits.

Effect of aeration on steady-state conditions in non- and partially aerated low-loaded biofilter

“…The HRT was approximately 50 min, which is in the range (20 min to 2 h) reported by Mendoza-Espinosa and Stephenson (1999) and Ha et al (2010b) for downflow aerated biofilters treating real and synthetic wastewater. Mendoza-Espinosa and Stephenson (1999) point out organic and nitrogen removal efficiencies above 80 % in fully aerated biofilters running at HLR from 1 to 10 m h -1 .…”

“…The aeration device introduced the air in an upward direction in order to keep dissolved oxygen (DO) concentrations above 2 mg O 2 L -1 in section TM-P3 (i.e., the reactor was partially aerated). This is one of the innovations of this work, since most of the previous studies with BAF (Villaverde et al 2000;Stephenson et al 2003;Lei et al 2009;Ha et al 2010b;He et al 2007) used fully aerated filters with the aeration device located at the bottom of the reactors. A backwashing system was included in order to remove the excess of both filtered material and biomass (sludge) produced during the biofilter operation.…”

“…Recent studies showed good performance for ammonia removal at HLR up to 3 m h -1 and air-flow rates from 18 to 200 L h -1 (Taghizadeh et al 2007;Schulz and Menningmann 2008;Lei et al 2009;Ha et al 2010b;He et al 2007;Rajakumar et al 2011) in fully aerated biofilters fed with higher ammonia concentrations ([100 mg NH 4 -N L -1 ). The HRT was approximately 50 min, which is in the range (20 min to 2 h) reported by Mendoza-Espinosa and Stephenson (1999) and Ha et al (2010b) for downflow aerated biofilters treating real and synthetic wastewater.…”

“…Most of the experiments developed with aerated biofilters used full aeration and the reactors were operated as secondary treatment, with air/water ratios between 4 and 10 to remove higher concentrations of carbon and ammonia, usually from 100 to 2,000 mg C L -1 and from 25 to 2,000 mg N L -1 , respectively (Mendoza-Espinosa and Stephenson 1999;Villaverde et al 2000;Osorio and Hontoria 2001;Stephenson et al 2003;Garzon-Zuniga et al 2005;Lei et al 2009;Ha et al 2010b;He et al 2007;Coetzee et al 2011;Rajakumar et al 2011). …”

“…Submerged biofilters have been used for on-site treatment (Coetzee et al 2011), secondary treatment of wastewater (domestic, industrial and stormwater effluents) (GarzonZuniga et al 2005;Osorio et al 2006;Farabegoli et al 2009;Liu et al 2010;Rajakumar et al 2011) or as a tertiary step to upgrade other treatment systems (Hidaka and Tsuno 2004;Liu et al 2008;Ha et al 2010b) and can be a promising alternative to retrofitting (Schulz and Menningmann 2008;Farabegoli et al 2009). The construction of biofilters as a tertiary/polishing step does not interfere with the operation of existing reactors and its maintenance is considered to be simple, as there is no need for sludge recycling and a final clarifier (Hidaka and Tsuno 2004).…”