Anaerobik arıtmada pH ve amonyak inhibisyonu

Özet

Amonyağın inhibe edici konsantrasyonlarına alıştırılmamış floküler ve granüler aşılarla karakterize edilen farklı anaerobik mikroorganizma gruplarının mezofılik şartlarda pH ve amonyak inhibisyonu karşısındaki davranışları toplam biyogaz üretiminin izlendiği metanojenik aktivite testi kullanılarak belirlenmiştir. Deneyler, dört farklı pH değerinde (6.8, 7.4, 7.8, 8.4) ve 6 farklı Toplam Amonyak Azotu (TAN) konsantrasyonunda (262 mg/l (kontrol), 1000, 1500, 2000, 2500, 3000) yürütülmüştür. Zamana karşı çizilen biyogaz üretim eğrileri kullanılarak eklenik metan üretim eğrileri elde edilmiştir. Eklenik metan üretim eğrilerinin modellenmesinde modifiye edilmiş Gompertz eşitliği kullanılmıştır. Değerlendirmeler sonucunda Gompertz modelinin, deneysel verilerin çok büyük bir kısmına iyi uyum gösterdiği bulunmuştur.

Abstract

The influences of pH and ammonia on methane production in the anaerobic treatment were investigated using two different sludge seeds. One of the seeds had a granular character whereas the other one had a flocular character. The sludge seeds used in the methanogenic activity tests were not exposed to high levels of ammonia at any stage, before the tests. Four different pH values (6.8, 7.4, 7.8, 8.4) and six different TAN (Total Ammonia Nitrogen) values (262 mg/L (control), 1000, 1500, 2000, 2500, 3000) were used in the study. Cumulative methane production curves for both of the sludge seeds were obtained using the biogas production curves at four different pH values and six different TAN values. The modified Gompertz equation employed as a model for cumulative methane productions. It was concluded that this equation fits a large fraction of the data very well. At certain combinations of high pH and high TAN values, however, the cumulative methane production data manifested an initial "hump" that cannot be predicted using the Gompertz equation. With flocular sludge seed, this happened at pH $geq$ 7.8 and with TAN $geq$ 1500-2000 mg/L. With granular sludge seed, this phenomenon was observed only at pH = 8.4 and with TAN $geq$ 1000 mg/L With both sludges, free ammonia was found to be much more inhibitory than the ammonium ion.