Efficient nitrogen (N) removal from slaughterhouse wastewater is a challenge for conventional activated sludge treatment processes. This project aimed to develop intermittently aerated sequencing batch reactor (IASBR) technology that could efficiently remove nitrogen from slaughterhouse wastewater. The IASBRs were operated at a laboratory-scale in the Environmental Engineering Laboratory at the National University of Ireland, Galway (NUI Galway) prior to the deployment of a pilot-scale unit at a local slaughterhouse in Co. Mayo. Modified IASBRs containing plastic media were operated at laboratory-scale only. The laboratory-scale units had working volumes of 10 l and were intermittently fed with slaughterhouse wastewater. The operational sequence of the IASBRs and the movement of all mechanical devices, including peristaltic pumps, stirrers and air pumps, were controlled by programmable logic controllers (PLCs). Dissolved oxygen (DO), pH and oxidation-reduction potential in the reactors were monitored in real time using electrodes, and were catalogued by a LabVIEW computer programme. The configuration of the modified laboratory-scale IASBR was the same as that of the original IASBR, but a bulk volume of 4.0 l of plastic biofilm carriers was added to the reactor. The biofilm carrier elements had a nominal diameter and length of 9.1 mm and 7.2 mm, respectively, and a specific weight of approximately 0.95 kg/l. The effective specific surface area of the biofilm carriers available for biofilm growth was 500 m2/m3. The reactors were operated on an 8-h cycle, which comprised four phases: 1.Fill; 2.React; 3.Settle; and 4.Draw/Idle. Over a 132-day study duration, at an average organic loading rate (OLR) of 1.2 g COD/l/day, the laboratory-scale IASBR achieved chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removals of 96%, 96% and 99%, respectively. Two operational strategies intermittent aeration (IA) and continuous aeration (CA) were used to treat the slaughterhouse wastewater at low DO levels. Under both regimes, respective TN removals of 94% and 91% were achieved. However, under IA, by maintaining low DO levels, electricity consumption associated with air supply can be reduced by up to 65%. Over a 120-day study duration, the modified laboratory-scale IASBR had an OLR of 1.18 ± 0.04 kg COD/m3/day and a nitrogen loading rate (NLR) of 0.11 ± 0.01 kg N/m3/day, and achieved COD, TN and TP removals in excess of 94%, 92% and 95%, respectively. As the performance of both systems was similar, and considering the cost of the biofilm media, the IASBR was deployed on-site. The pilot-scale IASBR was constructed at the Environmental Engineering Laboratory, NUI Galway, and deployed on-site at the slaughterhouse wastewater treatment plant for Western Proteins in Ballyhaunis, Co. Mayo. It was monitored for 402 days. The pilot-scale IASBR influent was taken from the balance tank in the slaughterhouse wastewater treatment plant that collects and treats wastewater generated in the slaughterhouse and the rendering plant. Both the waste sludge and effluent were discharged into a 150-l holding tank, from which a submersible pump pumped the tank holdings into the Western Proteins aeration tank, allowing the pilot-scale system to act as a loop on the Western Proteins wastewater treatment plant. The pilot-scale IASBR was operated under different aeration strategies (IA and CA), hydraulic retention times, sludge retention times, and OLRs. At a loading rate of around 0.5 kg COD/m3/day, efficient removals of pollutants (COD 97%, suspended solids (SS) 98%, TN 98%, and ortho-phosphorus (PO4-P) 99%) were achieved under the IA strategy, with production of an effluent (COD 117 mg/l, SS 26 mg/l, TN 8 mg/l, and PO4-P 0.2 mg/l) that met the discharge standards. The study on nitrous oxide (N2O) emission from IASBRs treating ammonium-rich wastewater showed that the influent readily biodegradable COD (rbCOD) concentration was considered to be a key factor to stimulate N2O emission to a high level in the oxygen-limited partial nitrification reactor via heterotrophic denitrification. Reduction of the influent rbCOD concentration, reduction of anoxic periods in operational cycles, and an increase in pH in the reactor would be the main options to avoid high N2O emission. This research project has developed a best available technology that has potentially huge implications for industries treating high-strength wastewater.

Research Recommendations for further research are:The development of an intelligent IASBR for treating slaughterhouse wastewater and other high-strength wastewaters. This technology can be applied by industries and local authorities to treat wastewaters, or to improve performance of the irexisting wastewater treatment facilities so as to reach stringent nutrient discharge standards. The expansion of the mathematical model in AQUASIM to better model the intermittently SBR systems and also to incorporate phosphorus removal.

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Zhan, X. Healy, M.   "Enhanced Nitrogen Removal for Slaughterhouse Wastewater Using Novel Technologies". Associated datasets and digitial information objects connected to this resource are available at: Secure Archive For Environmental Research Data (SAFER) managed by Environmental Protection Agency Ireland https://eparesearch.epa.ie/safer/resource?id=7c1f6b3c-f04f-102d-af1a-60cde515b757 (Last Accessed: 2025-01-20)

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SAFER-Data Display URL	https://eparesearch.epa.ie/safer/iso19115/display?isoID=180
Resource Keywords	slaughterhouse wastewater nitrogen technologies aerated sequencing batch reactor
EPA/ERTDI/STRIVE Project Code	2005-ET-MS-31-M3
EPA/ERTDI/STRIVE Project Theme	Waste and Resource Management
Resource Availability:	Public-Open
Limitations on the use of this Resource	It is critical that any 3rd party use of the information provided is properly cited when used in any: publication, website, web blog, presentation, report, technical report, or article. An automated citation is provided below and should be used as a guide for the proper citation for this resource.
Number of Attached Files (Publicly and Openly Available for Download):	4
Project Start Date	Saturday 1st January 2005 (01-01-2005)
Earliest Recorded Date within any attached datasets or digital objects	Tuesday 2nd October 2007 (02-10-2007)
Most Recent Recorded Date within any attached datasets or digital objects	Friday 7th November 2008 (07-11-2008)
Published on SAFER	Tuesday 3rd August 2010 (03-08-2010)
Date of Last Edit	Tuesday 17th August 2010 at 13:28:16 (17-08-2010)
Datasets or Files Updated On	Tuesday 17th August 2010 at 13:28:16 (17-08-2010)

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Description of Geographical Characteristics of This Project or Dataset
The pilot-scale IASBR was constructed at the Environmental Engineering Laboratory, NUI Galway,and deployed on-site at the slaughterhouse wastewater treatment plant for Western Proteins in Ballyhaunis, Co. Mayo. It was monitored for 402 days.The pilot-scale IASBR influent was taken from the balance tank in the slaughterhouse waste water treatment plant that collects and treats waste water generated in the slaughterhouse and the rendering plant. Both the waste sludge and effluent wered is charged into a 150-l holding tank, from which asubmersible pump pumped the tank holdings into theWestern Proteins aeration tank, allowing the pilot-scale system to act as a loop on the Western Proteins wastewater treatment plant.

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