This study investigated the use of ceramic membranes to remove total suspended solids (TSS), organics (expressed by chemical oxygen demand, COD), and bisphenol A (BPA) via microfiltration (MF, pore ...size 0.45 μm) and ultrafiltration (UF,
cutoff
150 kDa) in post-treatment of effluents from aerobic granular sludge reactors (GSBRs). The efficiency of removal of COD, BPA, and TSS in MF was similar to that in UF; however, it was achieved at a lower pressure, which reduces energy consumption during the filtration process. Despite the similar quality of the permeates in MF and UF, the permeate flux averaged almost 20% higher in UF than in MF. The rejection coefficients were 77–82% for COD and 48–100% for BPA. In both MF and UF, TSS were totally removed. In the integrated system of aerobic granular sludge reactor and membrane installation, total removal of COD was 92–95% and that of BPA was above 98%, independently of the membrane technique. The high efficiency of BPA removal in MF and UF, despite pore sizes in the MF and UF membranes larger than the BPA molecules, suggests that some part of the BPA was first bound by particulate organic matter in the biologically treated wastewater before this sorbed form was removed by the membranes. Furthermore, the high removal of COD and BPA, even in MF, was attributed to adsorption on the membranes, in addition to sieve retention.
The aim of this study was to determine the effectiveness of pollutant removal in sequencing batch biofilm reactors (with floating or submerged carriers) when treating nitrogen- and organic-rich real ...leachate generated during aerobic stabilization of the biodegradable municipal solid waste. A control reactor contained suspended activated sludge. The share of leachate in synthetic wastewater was 10%, which resulted in ratios of chemical oxygen demand and biochemical oxygen demand to total Kjeldahl nitrogen in the influent of ca. 11 and ca. 8.5, respectively. Regardless of whether the reactors contained carriers or not, the effectiveness of nitrification (84.2–84.3%) and of the removal of chemical oxygen demand (86.5–87.0%), biochemical oxygen demand (95.5–98.0%) and ammonium (88.9–89.3%) did not differ. However, the presence of carriers and their type determined in which phase of the cycle denitrification occurred. In the control reactor, denitrification took place during mixing phase with the effectiveness of ca. 43.2% (57.7% of the total nitrogen removal). During aeration, the oxygen content increased rapidly, thus reduced the possibility of simultaneous denitrification. In reactors with carriers, in the aeration phase, not only nitrification but also denitrification occurred. The increase in oxygen content in wastewater was slower, which could have caused dissolved oxygen gradients and anoxic zones in deeper layers of the biofilm and flocks. In the reactor with floating carriers, the effectiveness of denitrification and total nitrogen removal increased 1.23- and 1.10-times, respectively, as compared to the control reactor. The highest efficiencies (67.7% and 73.0%, respectively) were observed in the reactor with submerged carriers.
Bisphenol A (BPA) is an endocrine disruptor that is difficult to completely remove from wastewater by conventional biological methods. Increased post-treatment BPA removal with ceramic membranes is ...worth investigating because of these membranes’ mechanical and chemical stability and lifespan. To determine the effectiveness of ceramic membranes for post-treatment of biologically treated BPA-contaminated wastewater, microfiltration (MF) and nanofiltration (NF) were conducted. Both processes removed BPA completely at an initial BPA concentration of 0.3 ± 0.14 mg/L. Increased concentration of 0.7 ± 0.29 mg/L decreased BPA removal. MF removed at least 24 % of BPA, presumably because BPA was adsorbed on particulate matter, which was retained by the membrane, or adsorbed on its surface. NF removed up to thrice more BPA. MF and NF completely removed suspended solids and 40–60 % COD. Filtration capacity decreased with time due to fouling but did not depend on initial BPA concentration. BPA concentrations in municipal wastewater are typically lower than the lowest concentration tested, where MF completely removed BPA. Hence, MF ceramic membranes appear a promising solution for post-treatment of BPA-containing wastewater. MF can be used at a much lower transmembrane pressure than NF, requiring less energy to pump wastewater through the membrane, thus reducing costs.
This study compared the dewatering properties of aerobic granular and activated sludge from full-scale wastewater treatment plants, and determined how polymer dose and type affect granular sludge ...dewatering efficiency. At the same dose, granular sludge filtration cake had about 4% lower humidity than activated sludge cake. Aerobic stabilization improved only activated sludge dewatering. The granular sludge reactor had over 1.5 times more extracellular polymeric substances (1.8 times more alginate) per reactor volume than the activated sludge reactor, but the high polymer content did not decrease granular sludge dewatering. Granular sludge dewatered best with FLOPAM EM 840MEB, due to its composition (
n
-alkanes, isoalkanes, cyclic/aromatic hydrocarbons). With this polymer, sludge cake moisture was lowest (84.7 ± 0.4%) at 1.6 g polymer/kg MLSS. With all tested polymers, the lowest dose (0.2 g/kg MLSS) ensured low cake humidities; this dose was far lower than typical doses for activated sludge dewatering. Upgrading from activated to granular sludge technology significantly facilitates excess sludge management.
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio in wastewater in the reactor with typical geometry (height/diameter = ...2.1, superficial air velocity = 6 mm/s). The noted nitrification efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH₄⁺–N g total suspended solids (TSS)⁻¹day⁻¹, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria (AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia load. At the ammonia load of 0.3 ± 0.002 mg NH₄⁺–N g TSS⁻¹ day⁻¹, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass.
A bacterial community in activated sludge from a full-scale municipal wastewater treatment plant was monitored throughout the year with the use of FISH, RISA and DGGE techniques. In the investigated ...range of temperatures (11.9-21.6 degrees C), a rise in temperature resulted in a lower total bacteria richness, while organic load rate changes from 0.09 to 0.21 g COD x g TSS(-1) x d(-1) were positively correlated with the number of bands in RISA patterns. The most diverse pattern (29 different bands) was characteristic for the activated sludge sample collected at the end of January at wastewater temperature of 11.9 degrees C. The ammonia-oxidising bacteria community did not change during the study, and comprised of 4 different bacterial populations with one dominant species closely related to Nitrosospira sp. REGAU (GenBank accession number AY635572.1). The percentage of ammonia-oxidising bacteria in the activated sludge varied from 6.2 to 19.5% and depended on temperature (R = 0.61, p = 0:02) and organic load rate (R = -0.55, p = 0.04).
Data are reported from tests investigating cadmium desorption during subsequent cycles of adsorption/desorption via the application of chemical sorbents, including 2% sodium alginate, and sodium ...alginate with addition of poly(vinyl) alcohol (PV). Tests considered several different proportions of sodium alginate with PVA, including 1.5% alginate and 0.5% PVA, 2% alginate and 2% PVA, and 2% alginate with 5% PVA. Testing efforts also considered two types of activated sludge immobilized on alginate sorbents. Evidence indicated that adsorption by alginate, and alginate with PVA followed a second-order rate law. Researchers determined that increasing levels of PVA in alginate resulted in lower reaction rates. Desorption was achieved using mineral acids, e.g., hydrochloric acid and sulfuric acid.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study investigated the effectiveness of denitrification under aerobic conditions depending on nitrogen forms in synthetic wastewater (ammonium, or ammonium and nitrite). Activated sludge was ...cultivated in a sequencing batch reactor with municipal wastewater enriched by acetate. Poly-β-hydroxybutyrate (PHB) was accumulated in activated sludge to 0.35 g PHB g
−1
VSS. Activated sludge, cultivated in such conditions, was used in further experimental series. The duration of each series was 24 h. Two types of synthetic wastewater, with acetate as the carbon source, were used in this study. One type of wastewater contained only ammonium; the second one was enriched also by nitrite. The amount of nitrogen reduced by the microorganisms in the activated sludge was 22.5 mg N
red
l
−1
when ammonium was the only nitrogen source in wastewater, and a 3-fold increase was observed in the presence of two nitrogen sources: ammonium and nitrite. Simultaneous consumption of organic substances in wastewater (external source of electron donors) and intracellularly stored poly-ß-hydroxybutyrate in activated sludge (endogenous carbon source) was revealed. COD consumption to reduce 1 mg N-oxides, in series with wastewater containing ammonium, was 8.4 mg COD. However, in series using wastewater with ammonium and nitrite, a 3-fold decrease in COD/N
red
ratio was observed.
Tests evaluated the performance characteristics of two porous ceramic carriers with different internal active surface areas implemented as the stationary filling of reactors with immobilized ...activated sludge. Data are reported from experiments implemented for samples of municipal wastewaters treated under hydraulic retention times ranging from 15 to 70 minutes. Changes in the efficiency of organic compounds removal are detailed. Findings showed that the contribution of oxidation, biomass synthesis, denitrification, and intracellular storage for the removal of organic compounds depended on the type of carrier used and the hydraulic retention time. Researchers determined that more than 20% of organic loading in influent to reactors I and II was used for cellular oxidation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Tests were implemented to identify the particular process involved in the removal of carbon from wastewater. Potential pathways considered in the effort included biomass synthesis, oxidation, ...denitrification, and accumulation. Experiments investigating these issues were conducted in a sequencing batch reactor system in two series with different organic carbon compounds to nitrogen compounds ratios. The project utilized an organic carbon loading of activated sludge of 0.07 gCOD/g d. Evidence showed that the organic carbon removal efficiency was highest (98%) as COD/N ratio of 13, and remained high (85) at COD/N ratio of 3. Changes in the processes of biomass synthesis, denitrification, and intracellular accumulation with changes in the COD/N ratio in waste are detailed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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