Application Of Anaerobic Treatment Research Articles

Pilot‐scale sequential anaerobic–aerobic biological treatment of waste streams from a paper mill

The pulp and paper industry produces a large quantity of wastewater containing recalcitrant organic compounds. In this study, a pilot‐scale anaerobic–aerobic sequential system was employed to treat four different waste streams produced in a kraft pulp and paper mill. The system consisted of a 2.3 m3 packed‐bed anaerobic digester and a completely mixed activated sludge process. Under the applied organic loading rate to the anaerobic digester (0.2 to 4.8 kg‐COD m−3 d−1), a COD removal efficiency of 50–65% was achieved. After the anaerobic treatment, the BOD/COD ratio of the effluent was low (0.12 ± 0.03), suggesting that additional pretreatment is necessary for the digester effluent to be further polished aerobically. Combined with the aerobic treatment, the overall COD removal efficiency was up to 70% for the substrates evaluated. Air purging before feeding sulfide‐containing substrate was shown to be effective for removing sulfide toxicity in the digester. Kinetic analysis showed that the pseudo‐first‐order degradation rate constants of the evaluated substrates are 0.28–0.46 d−1 in the anaerobic digester, with a methane production yield of 0.22–0.34 m3‐CH4 kg‐COD−1 at standard temperature and pressure (0°C, 1 atm). These values are comparable to those found for other industrial substrates, indicating that an anaerobic process is a sound treatment alternative for the evaluated waste streams. The quality of biogas produced by the substrates was excellent, containing ∼80% of methane. The application of anaerobic treatment has the potential of significantly improving the energy footprint of the pulp and paper industry. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 359–368, 2014

The origin and population dynamics of annually re-occurring Paratanytarsus grimmii (Diptera: Chironomidae) colonising granular activated carbon (GAC) adsorbers used in potable water treatment

Various sampling techniques were employed to study the population dynamics and identify the origin of annually re-occurring infestations of Paratanytarsus grimmii in granular activated carbon (GAC) adsorbers. Larvae overwintered in all adsorbers studied and are the main source of endemic persistent infestations. Significant differences in larval densities were identified between the down-flow cell (mean of 61 larvae per 0.3 l of GAC) and the up-flow cell (mean of 14 larvae per 0.3 l of GAC) of each adsorber. Larvae were distributed uniformly with no significant difference in density at any depth through the 2-m carbon column. Application of anaerobic treatment as a control measure was ineffective at low temperatures due to a slow down in chironomid metabolism. During summer months, ovipositing females have access to all locations within the GAC adsorber building by flight, leading to immediate re-colonisation of anaerobically-treated adsorbers. Regeneration of GAC in individual cells served only to reduce larval numbers but not remove them completely, particularly when only one of the two cells is regenerated at any one time.

Reactor performance and microbial community of an EGSB reactor operated at 20 and 15°C

To investigate the effects of low temperatures on the performance and microbial community of anaerobic wastewater treatment. An expanded granular sludge bed (EGSB) reactor was employed to treat synthetic brewery wastewater at 20 and 15 degrees C. Reactor performance was represented by chemical oxygen demand (COD) removal efficiency, while the microbial community was analysed using denaturing gradient gel electrophoresis (DGGE) and clone technology. When the hydraulic retention time (HRT) was maintained at 18 h, COD removal efficiencies above 85% were obtained at both 20 and 15 degrees C, with influent COD concentrations up to 7300 and 4100 mg l(-1), respectively. At 15 degrees C, the COD removal efficiency was more easily manipulated by increasing the influent COD concentration. DGGE and clone results for both temperatures revealed that Methanosaeta and Methanobacterium were two dominant methanogens, and that the majority of the eubacterial clones were represented by Firmicutes. When the temperature decreased from 20 to 15 degrees C, both archaeal and eubacterial communities had higher diversity, and the proportion of Methanosaeta (acetate-utilizing methanogens) decreased markedly from 60.0% to 49.3%, together with an increase in proportions of hydrogen-utilizing methanogens (especially Methanospirillum). The feasibility of psychrophilic anaerobic treatment of low and medium strength organic wastewaters was demonstrated, although lower temperature could significantly affect both reactor performance and the anaerobic microbial community. The findings enrich the theory involving the microbial community and the application of anaerobic treatment in a psychrophilic environment.

Application of anaerobic digestion to the treatment of agroindustrial effluents in Latin America

A 1994 survey of high rate anaerobic reactors employed in the treatment of agroindustrial effluents in Latin America is presented. Data including number, volume and type of reactors, their evolution with time and type of effluents are discussed. Latin America has an increasing and significant participation in the application of anaerobic treatment to agroindustrial effluents. In particular, the design parameters of already operating reactors and the impact of applying this technology to the most typical effluents are analyzed. The equivalent energy of biogas that can be produced through this technology is given.

Application of the upflow anaerobic sludge bed (UASB) process for treatment of complex wastewaters at low temperatures

The feasibility of the upflow anaerobic sludge bed (UASB) process for the treatment of potato starch wastewater at low ambient temperatures was demonstrated by operating two 5.65-L reactors at 14 degrees C and 20 degrees C, respectively. The organic space loading rates achieved in these laboratory-scale reactors were 3 kg COD/m(3)/day at 14 degrees C and 4-5 kg COD/m(3)/day at 20 degrees C. The corresponding sludge loading rates were 0.12 kg COD/kg VSS/day at 14 degrees C and 0.16-0.18 kg COD/kg VSS/day at 20 degrees C.These findings are of considerable practical importance because application of anaerobic treatment at low ambient temperatures will lead to considerable savings in energy needed for operating the process. As compared with various other anaerobic wastewater treatment processes, a granular sludge upflow process represents one of the best options developed so far. Although the overall sludge yield under psychrophilic conditions is slightly higher than under optimal mesophilic conditions, this doesn't seriously hamper the operation of the process. The extra sludge yield, due to accumulation of slowly hydrolyzing substrate ingredients, was 4.75% of the COD input at 14 degrees C and 1.22% of the COD input at 20 degrees C.

Devernalization of Spring Rye by Anærobic Conditions and Revernalisation by Low Temperature

A PREVIOUS letter in NATURE1 presented evidence to show that in winter rye (var. Petkus) anaerobic conditions at normal temperatures (20° C.) when alternated with aerobic conditions at 1° C. quantitatively annul the vernalizing effect of low temperature. It appeared possible, therefore, that spring rye of the same variety might be devernalized by the application of anaerobic treatment at 20° C. Previous work2,3 has shown that the process of vernalization in winter rye decreases the number of leaves produced on the main axis before flower initiation, as well as decreasing the period of time required to reach anthesis. An increase in these characteristics in spring rye after anaerobic treatment would thus indicate a process of devernalization.