Loredana Stante

Biological phosphorus removal by pure culture of Lampropedia spp.

Abstract Lampropedia spp. is a Gram-negative, Neisser-positive coccus that was isolated from EBPR (enhanced biological phosphate removal) activated sludge laboratory plants operating on dairy and piggery wastewaters. In aerobic growth tests carried out on sodium acetate, Lampropedia spp. stored PHB up to 12% w/w. Biomass yield was estimated at 0.55 g VSS.g−1 HAc and specific growth rate at 0.045 h−1. The experimental maximum acetic acid removal rate was 71.86 mg HAc.g−1 VSS.h−1 with a semisaturation constant of 71.78 mg.l−1. Batch tests were carried out to check whether Lampropedia spp. was capable of enhanced biological phosphorus removal. Under anaerobic conditions, Lampropedia spp. sequestered acetate and stored PHB with an average conversion factor of 0.33 mg PHB.mg−1 HAc. The measured maximum PHB storage capacity was 31% w/w, with a maximum specific PHB accumulation rate of 17 mg PHB.g−1 VSS.h−1 and a specific anaerobic acetate uptake rate of 57 mg HAc.g−1 VSS.h−1. The experimental ratio between phosphorus released and acetate taken up was low, on average 0.044 mg PO4-P.mg−1 HAc, with a specific rate ranging from 1.7 to 3.6 mg PO4-P.g−1 VSS.h−1 at pH 7.5. Despite the low figure, fractionation analyses showed that in anaerobic conditions the released phosphate comes from cell polyphosphate degradation. Therefore, all the results allow us to conclude that Lampropedia spp. can be classified amongst the phosphorus accumulating bacteria

Anaerobic treatment of cheese whey with a downflow-upflow hybrid reactor

Abstract ENEA (Italian Agency for New Technology for the Energy and for the Environment) research on the anaerobic treatment of raw cheese whey started in 1990 with the objective of developing a technology suitable for medium-size cheese factories that have growing disposal problems and cannot afford high investment costs for whey valorisation technologies (such as whey protein and lactose recovery, spray drying, etc.). The first attempt was to run a mesophilic hybrid upflow reactor, that was able to reach high removal performances but showed pH unstability which led to failure. In order to obtain better process control, experiments continued on a two-phase CSTR (completely stirred reactor) system that gave good results in terms of stability. To couple process stability and high loads, a new reactor called a downflow-upflow hybrid reactor (DUHR) has been designed. The reactor was able to reach B v (volumetric organic loading rate) values around 10 000 mg COD l −1 day −1 , with 98% COD removal and effluent soluble COD (COD sol ) values close to 1000 mg.l −1 ; no external addition of alkalinity was required to maintain a stable pH that was constantly around 6.5–6.7 in the downflow pre-acidification chamber and around 7.5 in the bio-methanation upflow chamber.