A. Tilche

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.

Pelletization of biomass in a hybrid anaerobic baffled reactor (HABR) treating acidified wastewater

Abstract Pelletization of biomass was observed in a hydrid anaerobic baffled reactor treating molasses wastewater. The use of highly acidic molasses wastewater as substrate resulted in pelletization of the sludge within 30 days of operation. Change of substrate from acidified molasses to protein-rich molasses did not affect the process of pelletization. The biological pellets were able to grow and maintain their sludge settling-characteristics. The pellets were formed in all the three chambers of the reactor. The predominant mathanogenic bacteria observed were Methanosarcina sp. in the first chamber and Methanothrix sp. in the rest of the reactor. Other bacteria morphologically similar to Methanobrevibacter, Methanococcus and Desulfovibrio were also observed. The reactor was able to remove 73% of soluble COD (Chemical Oxygen Demand) at the loading rate of 20 kg COD/m 3 day. Methane production rates exceeded five volumes per day per unit volume of the reactor.

Fate of residuals in nitrification-denitrification treatment of piggery wastewaters

Abstract A careful appraisal of piggery wastewaters should be made mainly because of their high content of organic constituents together with the nitrogen and stringent effluent limitations involved. Specific emphasis should be given to the COD of the wastewater as it contains, aside from a biodegradable portion, a residual fraction which persists throughout the treatment process. Experimental evaluations indicated that the effluent of a laboratory-scale SBR contained significant amounts of non-biodegradable COD. Since SBR was primarily operated to achieve nitrification-denitrification, a method previously developed for the assessment of the influent soluble inert COD, S 1 was modified in a way to reflect the possible impact of the nitrification and denitrification processes. The paper also summarizes the performance of SBR with respect to its nitrogen removal potential from piggery wastewaters.

Post-treatments of anaerobic effluents

Post-treatments are necessary if anaerobic effluents need to be discharged into surface waters, because anaerobic digestion alone is not able to produce effluents that can meet the discharge standards applied in most industrialized countries, particularly for suspended solids, particulate COD, nitrogen, phosphorus and sulphides. This paper has the aim to present some results obtained in the recent years in our laboratory, where different comprehensive processes that include anaerobic digestion have been studied. Discussion will regard: 1) the ANANOX (ANaerobic-ANoxic-OXic) process for the treatment of municipal wastewater; 2) a process studied for the biological removal of C, N and P from piggery wastewater that has a hybrid anaerobic/anoxic reactor as the first treatment step; 3) the use of a Sequencing Batch Reactor for the post-treatment of digested cheese whey mixed with cheese factory cleaning waters.