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.Abbreviations ABR Anaerobic Baffled Reactor - Bv organic volumetric loading rate (gCOD·L^-1·d^-1) - BV bed volumes - F/M food to microorganism ratio or sludge loading rate (gCOD·g.VSS^-1·d^-1) - HRT hydraulic retention time (t) - JHB University of Johannesburg nutrient removal process - p.e. person equivalent - Qrd recycle for denitrification flow rate - Qrs sludge recycle flow rate - SBR Sequencing Batch Reactor - TKN Total Kjeldahl Nitrogen - VCF Volumetric Concentration Factor (vol. permeate/vol. retentate)     

对处理不同废水的几种厌氧消化器生物量中优势产甲烷菌的观察

The biomass taken from AF, ABR, and UASB digesters treating municipal wastewater, swine waste and molassese stillage wastewater, municipal and molassese stillage wastewater respectively, were observed by light, epifluorescence microscope and scanning electron microscope. The prevalent methanogens in these digesters were Methanothrix. Exception for ABR carried out to treat swine waste, Methanosarcina with three forms of aggregations, cysts, and granules were presented in other digesters. A suggestion can be made that reactors with packing materials, such as, anaerobic filters, anaerobic contact beds and two-phase methanation digesters can be used to accumulate Methanosarcina due to their morphological, mu max, and Ks characteristics, in order to increase the wastewater treatment efficiency further.     

Denitrification with Thiobacillus denitrificans in the ANANOX® process

Summary Thiobacillus denitrificans is a chemoautotrophic microorganism which is able to denitrify utilizing sulphides as electron donors. It has been found in the anoxic chamber of a ANANOX pilot plant, where the effluent from an anaerobic step is mixed with a clarified nitrified stream. Its presence resulted in a high denitrification rate, oxidizing sulphide to sulphate, and reducing nitrate to nitrogen gas.     

On trusting ethnography: serendipity and the reflexive return to the fields of Gujarat

We draw on David Pocock's fieldwork of the 1950s in central Gujarat, India, as a comparative resource to think about social change and anthropological knowledge. Revisiting where Pocock had been through new fieldwork, we were encouraged to think about the ways in which places are accessed and subsequently understood. Against our conscious will, the pathways we were able to take through the field strongly resembled those Pocock took sixty years earlier. The coincidence is such that the material casts shadows of doubt over the potency of terms such as ‘serendipity’ and ‘chance’ to characterize key moments of ethnographic fieldwork. Against the primacy given to the self in much reflexive anthropology, we demonstrate that the personal attributes of the anthropologist might influence the production of ethnographic research less than is generally assumed. The double bind of our ‘reflexive return’ comes from revisiting an anthropological field and experiencing the agency of that field in making what we can know.