Dairy manure wastewater in serial UASB reactors for energy recovery and potential effluent reuse

Abstract

-This manuscript addresses the use of dairy manure wastewater (DMW) as a substrate for methane production in a high rate system -two serial UASB reactors -and the characterization of the effluent in the different phases of the treatment. Two experimental conditions were applied. In the first, the organic load rate (OLR) was 6.2 gCOD total L -1 d -1 and the hydraulic retention time (HRT) was 12 days, whereas in experiment 2 they were 14.2 gCOD total L -1 d -1 and 7.5 days, respectively. The reactors showed a high capacity of removal of COD and solids, i.e., above 71%, which led to bioenergy productivities of 0.55 and 0.73 L CH 4 L -1 d -1 in experiments 1 and 2, respectively. The methane yield in UASB1 was 0.19 and 0.08 L CH 4 g COD rem 1 , respectively, in experiments 1 and 2. The methane yield in UASB1 was greater than UASB2, with approximately 70% of methane content in the biogas in this reactor.The effluent characterization showed micro and macronutrients -some in high concentrations, as nitrogen, phosphorous, K, and Fe between 12.1 and 521.4 mg L -1 , and others in low concentrations, as Ca, Mg, Zn and Mn between 0.6 and 13 mg L -1 . Na was not removed from the UASB systems and its concentration in the effluent was raised to 23.5% in comparison with the substrate.

Granular Sludge Bed Processes in Anaerobic Digestion of Particle-Rich Substrates

“…Due to the typical short HRT of UASB, feed particles must somehow be retained longer than HRT to be degraded but mechanisms for such are not described in the literature so indirect evidence is considered. UASB reactors treating particle-rich manure slurries accumulate suspended solids from the feed, forming an additional suspended fraction together with the granules [8,9] and a significant fraction of feed particles can be digested and contribute significantly to methane production at low HRT [11]. The density of such feed particles can be low so that they remain suspended during storage and in feed containers [11], implying that their sedimentation characteristics are such that they should have reactor retention time similar to HRT unless somehow 'captured' by the sludge bed.…”

“…Granules are formed by the aggregation of microorganisms that develop into dense masses with sedimentation velocity high enough to avoid washout even under high hydraulic load [7]. It is observed that UASB reactors treating particle-rich manure slurries also accumulates suspended solids from the feed, forming an additional suspended fraction together with the granules [8,9]. The influence of such solids on AD is not understood well, leading some experts to claim that granular sludge bed (GSB) processes may not be appropriate for particle-rich substrates.…”

“…Contois kinetics (Equation (9)) takes effects of active biomass (X biom ) and its ratio to the slowly degradable substances (Xc) in the substrate into account. dX C dt = −K m,dis X c X biom K s,dis + X c X biom X biom (9) where K m,dis is maximum disintegration rate in d −1 , K s,dis is a dimensionless half-saturation coefficient. Dimock et al [89] studied the influence of the size of protein particles on hydrolysis.…”

Minitomateiro consorciado com adubos verdes fertirrigados com efluente tratado de laticínio

“…Isso se justifica mediante o fato de que embora o tratamento anaeróbio diminua a DQO (demanda química de oxigênio), SST (sólidos suspensos totais) e SSV (sólidos suspensos voláteis), as concentrações de nutrientes pós-tratamento, como nitrogênio e fósforo, são importantes fontes de nutrientes às culturas. Para disposição deste efluente em corpos hídricos esta condição não é adequada, entretanto, do ponto de vista agrícola isso se torna interessante uma vez que este efluente tratado anaerobicamente pode apresentar valor econômico como fertilizante (BAME et al 2014;FOXON et al, 2004;MONTOYA et al, 2017).…”