ARS | Publication request: NITRIFICATION TREATMENT OF SWINE WASTEWATER WITH ACCLIMATED NITRIFYING SLUDGE IMMOBILIZED IN POLYMER PELLETS

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 1999
Publication Date: N/A

Interpretive Summary: Nitrogen pollution is a major concern for swine production. Nitrogen in the ammonia form can volatilize and subsequently settle in sensitive environments causing stimulation of deleterious plant and microbial growth. Fortunately, there are natural processes to keep nitrogen in balance, and allow it to serve its essential role in the environment. To manage ammonia, scientists and engineers have used the microbial process of nitrification to convert ammonia to nitrate. The process is a standard part of municipal and industrial wastewater treatment. One major improvement in nitrification technology was made in Japan. They used large populations of adapted nitrifying bacteria entrapped in polymer resins to achieve conversion rates that are much faster than those occurring in conventional waste treatment systems. However, this technology had neither been used in the USA for municipal wastewater treatment nor anywhere in the eworld for nitrification of animal wastewater which has much higher concentrations of ammonia and organic carbon. Our approach was to use an acclimated bacterial sludge (ABS) obtained from a nitrifying sludge that was acclimated to lagoon swine wastewater. We found that immobilized ABS can rapidly nitrify lagoon wastewater with rates comparable to those found in Japan for municipal systems. Thus, immobilized pellets appear to be a useful technology for swine wastewater treatment. One of their first applications may be the retrofit of anaerobic swine lagoons for fast and efficient removal of ammonia.

Technical Abstract: Nitrification of ammonia (NH4) is a critical component for improved systems of animal wastewater treatment. One of the most effective processes uses nitrifying microorganisms encapsulated in polymer resins. It is used in Japan in municipal wastewater treatment plants for higher nitrification rates, shorter hydraulic retention times (HRT), and lower aeration treatment cost. We evaluated whether this technology could be adapted for treatment of higher-strength lagoon swine wastewaters containing approx. 230 mg NH4-N/L and 195 mg BOD5/L. A culture of acclimated lagoon nitrifying sludge (ALNS) was prepared from a nitrifying biofilm and successfully immobilized in 3- to 5-mm polyvinyl alcohol (PVA) polymer pellets. Swine wastewater was treated in aerated, suspended bioreactors with a 15% (w/v) pellet concentration using batch and continuous flow treatment. In batch treatment, only 14 h were needed for nitrification of ammonia. Ammonia was snitrified readily, decreasing at a rate of 16.1 mg NH4-N/L/h. In contrast, it took 10 d for a control (no-pellets) aerated reactor to start nitrification; furthermore, 70% of N was lost by air stripping. In continuous flow treatment, nitrification efficiencies of 95% were obtained with ammonia loading rates of 418 mg-N/L-reactor/d (2.73 g-N/g-pellet/d) and HRT of 12 h. In all cases, the ammonia-N removed was entirely recovered in oxidized N forms. Nitrification rates obtained in this work were comparable to rates obtained with municipal systems. This indicates that immobilized ALNS pellets were not greatly affected by high ammonia or BOD concentration of swine wastewater. Thus, immobilized pellet technology can be adapted for fast and efficient removal of ammonia contained in anaerobic swine lagoons using acclimated microorganisms.