Influence of supplements and pre-treatment of concentrated secondary sludge on the production of biogas

Odvoz odpadnega biološkega blata postaja vse večji problem na bioloških čistilnih napravah, saj lahko predstavlja do 50 % stroškov obratovanja. Anaerobna razgradnja ima tu pomembno vlogo, ker se med procesom organska snov pretvarja v bioplin, ki se uporablja kot obnovljivi vir energije. Cilj magistrske naloge je bil raziskati, ali lahko z dodajanjem bioloških preparatov v reaktor ali predhodno obdelavo zgoščenega sekundarnega (aktivnega) blata izbojšamo produkcijo bioplina ter hkrati zmanjšamo končno vsebnost organske snovi v anaerobno obdelanem blatu na Cenralni čistilni napravi Domžale-Kamnik. V ta namen je bilo izvedenih 5 eksperimentov v dveh pilotnih bioreaktorjih (en kontrolni in en poskusni) s prostornino 200 L. Kot inokulum je bil uporabljen digestat iz industrijskega anaerobnega anaerobni bioreaktorja. Poskusi so trajali 30 dni, tekom katerih smo dodajali po 10 L (trikrat) oziroma 20 L (dvakrat) zgoščenega sekundarnega blata kot substrata. Za izboljšanje produkcije bioplina iz zgoščenega sekundarnega blata smo preizkusili dva encimska oziroma bakterijska preparata (MethaPlus L120, Agrovit in BioCat+™, Citadel) ter mehansko dezintegracijo (hidrodinamsko kavitacijo) kot metodo predhodne obdelave. Med poskusi smo merili vrednost pH, alkalinitete ter vsebnost Kjeldahlovega in amonijskega dušika, kratkoverižnih maščobnih kislin, kemijske potrebe po kisiku in vsebnost organske snovi. On-line smo merili volumen nastalega bioplina. Produkcija bioplina se je najbolj povečala pri uporabi mehanske dezintegracije blata ob dvojni prostorninski volumski obremenitvi in sicer do 10,8 %. Pri dodajanju encimskega produkta ob enojni prostorninski volumski obremenitvi se je produkcija povečala za 6,3 %, medtem ko je dodajanje bakterijskega pripravka produkcijo zmanjšalo za 8 %.Vsebnost organske snovi se med poskusi ni zmanjšala.The disposal of waste sludge is a problem of growing importance in waste water treatment plants. It can represent up to 50 % of operating costs. Anaerobic digestion plays an important role due to its ability to transform organic matter into biogas which is used as a renewable source of energy. The aim of the study was to examine whether the addition of supplements or pre-treatment of concentrated secondary (waste-activated) sludge could improve the production of biogas from it and also reduce the final content of organic matter in the digestate in Domžale-Kamnik wastewater treamtment plant (WWTP). Five experiments were performed in two pilot-scale CSTR bioreactors (one as the experimental and the other as the control reactor) with total volume of 200 L. Digestate from a full-scale anaerobic digester was used as an inoculum. Experiments were conducted for 30 daysduringthat 10 L (three times) and 20 L (two times) of concentrated secondary sludge was added as a substrate. To enhance the biogas production in anaerobic digestion process two different commercial enzymatic/bacterial supplements (MethaPlus® L120, Agrovit and BioCat+™, Citadel) and mechanical desintegration (hydrodinamic cavitation) as a pre-treatment process were applied. During the process pH, alkalinity, Kjeldahl\u27s and ammonium nitrogen, shortchain fatty acids, chemical oxygen demand and organic matter were monitored off-line and volume of biogas on-line. The mechanical pre-treatment at double volumetric loading rate enhanced the biogas production most successfully, up to 10,8 %. Addition of enzymatic supplement at single volumetric loading rate enhanced the biogas production up to 6,3 %. Meanwhile, addition of bacterial supplement at single volumetric loading rate reduce biogas production up to 8 %.Content of organic matter did not decreased during experiments

A synergic approach for nutrient recovery and biodiesel production by the cultivation of microalga species in the fertilizer plant wastewater

The combination of wastewater treatment and biodiesel production using algal cultivation was studied in the present work. The two main goals of the work were achieved by the cultivation of freshwater microalgae such as Chlamydomonas sp., Scenedesmus ecornis, and Scenedesmus communis in two different dilutions of fertilizer plant wastewater (FWWD1 and FWWD2) collected from Yara Suomi 0y, Finland. The growth pattern of different algal species in FWWD1 and FWWD2 was observed. The effect of pH on biomass concentration, lipid content, biomass productivity, and lipid productivity by all three algal species in FWWD1 and FWWD2 were monitored. The maximum biomass concentration and productivity were observed in FWWD1 at pH7.5 for Chlamydomonas sp. and at pH 8.5 for S. ecornis and S. communis. The maximum lipid content was detected in Chlamydomonas sp at pH5.5, followed by S. ecornis and then S. communis at pH 7.5 in FWWD2 obtained after co-solvent extraction method. The most significant removal percentage of COD by all algal species were observed in FWWD1, whereas the highest removal percentage of TN and TP were detected in FWWD2, respectively. The fatty acid methyl ester (FAME) characterization of each algal species in FWWD1 and FWWD2 at their optimum pH was investigated to determine the quality of obtained biodiesel.Peer reviewe

Wood-Based Cellulose-Rich Ultrafiltration Membranes: Alkaline Coagulation Bath Introduction and Investigation of Its Effect over Membranes’ Performance

In this study, wood-based cellulose-rich membranes were produced with a novel approach to casting procedure. Flat-sheet membranes were prepared from birch biomass pretreated with deep eutectic solvent and dissolved in ionic liquid-dimethylsulfoxide system via phase inversion method. Alkaline coagulation bath filled with sodium hydroxide solution was added to the process before a water coagulation bath and aimed to improve membranes’ performance. The effect of NaOH coagulation bath on the membrane was studied based on two NaOH concentrations and two different treatment times. The characterisation methods included measuring pure water permeabilities, polyethylene glycol 35 kDa model solution retentions, hydrophilicity, zeta potential, and chemical structure. Additionally, suitability of the membranes for removing residual phosphorous from a municipal wastewater treatment plant’s effluent was studied. The study revealed that introduction of the alkaline coagulation bath led to additional removal of lignin from membrane matrix and increase in the filtration capacity up to eight times. The resulting membranes can be characterised as very hydrophilic, with contact angle values 11.9–18.2°, negatively charged over a wide pH range. The membranes with the highest permeability, 380–450 L/m2·h·bar, showed approximately 70% phosphorus removal from purified wastewater, good removal of suspended solids, and low irreversible fouling tendency

Effect of humic acid on anaerobic digestion of cellulose and xylan in completely stirred tank reactors : inhibitory effect, mitigation of the inhibition and the dynamics of the microbial communities

Inhibition effect of humic acid (HA) on anaerobic digestion of cellulose and xylan and the mitigation potential of the inhibition were evaluated in controlled fed batch reactors at 30 °C and a hydraulic retention time (HRT) of 20 days. Reactor performances were evaluated by biogas production and metabolite measurements for 220 days. Microbial population dynamics of the reactors were monitored with next-generation 16S rRNA gene sequencing at nine different sampling times. Our results showed that increasing levels of HA inhibited the hydrolysis efficiency of the digestion by 40% and concomitantly reduced the methane yield. Addition of hydrolytic enzymes helped to reverse the negative effects of HA, whereas calcium addition did not reverse HA inhibition. Microbiological analyses showed that the relative abundance of hydrolytic/fermentative bacterial groups such as Clostridiales, Bacteroidales and Anaerolineales was significantly lowered by the presence of HA. HA also affected the archaeal populations. Mostly hydrogenotrophic methanogens were negatively affected by HA. The relative abundance of Methanobacteriaceae, Methanomicrobiales-WCHA208 and Unassigned Thermoplasmata WCHA1-57 were negatively affected by the presence of HA, whereas Methanosaetacea was not affected.</p

Effect of humic acid on anaerobic digestion of cellulose and xylan in completely stirred tank reactors: inhibitory effect, mitigation of the inhibition and the dynamics of the microbial communities.

Inhibition effect of humic acid (HA) on anaerobic digestion of cellulose and xylan and the mitigation potential of the inhibition were evaluated in controlled fed batch reactors at 30 °C and a hydraulic retention time (HRT) of 20 days. Reactor performances were evaluated by biogas production and metabolite measurements for 220 days. Microbial population dynamics of the reactors were monitored with next-generation 16S rRNA gene sequencing at nine different sampling times. Our results showed that increasing levels of HA inhibited the hydrolysis efficiency of the digestion by 40% and concomitantly reduced the methane yield. Addition of hydrolytic enzymes helped to reverse the negative effects of HA, whereas calcium addition did not reverse HA inhibition. Microbiological analyses showed that the relative abundance of hydrolytic/fermentative bacterial groups such as Clostridiales, Bacteroidales and Anaerolineales was significantly lowered by the presence of HA. HA also affected the archaeal populations. Mostly hydrogenotrophic methanogens were negatively affected by HA. The relative abundance of Methanobacteriaceae, Methanomicrobiales-WCHA208 and Unassigned Thermoplasmata WCHA1-57 were negatively affected by the presence of HA, whereas Methanosaetacea was not affected.Sanitary Engineerin