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Bicarbonate is an alternative carbon source for production of photosynthetic microalgae, although sparging of CO2-enriched gas is commonly practised, its efficiency seems to be scarcely considered. This study evaluated the photosynthetic activities of microalgae (Tetradesmus wisconsinensis) using chlorophyll fluorescence under different concentrations of bicarbonate (HCO3 -) and CO2. Chlorophyll fluorescence analysis showed noticeable difference in photosynthetic activity between the bicarbonate (HCO3 -) and CO2 supplied cultures. The JIP-test parameters obtained for the cultures supplemented by HCO3 - or CO2 were distinct, but of similar values in quantum yield of PSII. The typical polyphasic rise, called the OJIP curves, showed a typical difference between the treatments at the J and I inflection of the fluorescence transient curve. Both HCO3 - (20 mM) and CO2 (5%, v/v) gave higher biomass yield than the other carbon regimes, i.e., 673 ± 12 and 658 ± 11 mg L-1, respectively. We concluded that bicarbonate resulted in similar photosynthetic yield as CO2 supplementation. [ABSTRACT FROM AUTHOR]

The impact of H2 consumption, by homoacetogens, on the overall hydrogen yield in mixed culture fermentation is the focus of this study. Batch reactors were used to test the ability of anaerobic digested sludge, heat treated to eliminate methanogens, to produce and consume molecular hydrogen. The measured average hydrogen production rate from 4.2 g glucose/L was 44±4 mmol H2/L sludge · d, while the H2 consumption rate varied much more, in the range from 4 to 62 mmol H2/L sludge · d. Hydrogen consumption rate depends on acetic acid concentration, headspace H2 partial pressure and mass transfer rates. Different but relatively long lag-phases for hydrogen consumption were observed. It is concluded that homoacetogenesis can have a significant negative effect on bio-H2 production by mixed cultures, limiting the possibilities for sustainable solutions. [ABSTRACT FROM AUTHOR]

This paper presents a strategy in which mixed biological cultures are exposed to oscillating concentration levels, to improve the potential for coexistence of desired bacterial species. A mechanistic mathematical model is constructed to investigate and illustrate this strategy. This paper is focused on competition between nitrifying, dcnitrifying and aerobic heterotrophic bacteria in a CSTR with sludge recycle. For nitrifying and aerobic heterotrophic cultures, the effect of sinusoidal oscillations in DO levels with an amplitude of 1.0 mg/l is a16% specific growth rate reduction compared to that at a constant DOlevel. The denitrifiers growth rate is increased by an average of 59%, compared to the constant DO level situation. A similar strategy has been tested in a pilot plant. It is concluded that the influence onspecific growth rates is a function of the amplitude of the oscillations. The effects are greatest when concentrations fluctuate around the half saturation concentration of rate limiting component(s). ) 1998 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]

Biofilm activity, behaviour and our ability to control biofilms depends to a large extent on mass transfer phenomena in the biofilm, at the biofilm-liquid interface and in the bulk liquid. Biofilms respond to changing mass transfer conditions by adjusting morphology, therebyoptimising the exchange of matter with their surroundings. Observingbiofilm morphology and mass transfer in relevant fluid dynamic conditions can therefore yield essential information to understand and model biofilm behaviour. Lack of such knowledge, as the case is with regards to biofilm behaviour in various porous media, such as sandstone reservoirs, limits our ability to predict biofilm effects. A transparent porous media replica of a sandstone reservoir with cybernetic image processing has been designed to study biofilm related transport phenomena in porous media. The porous medium was inoculated with a mixed bacterial culture and fed a sterile nutrient solution in a once through flow mode. The biofilm was observed by microscopy with automated image analysis. This novel integrated software/hardware cybernetic design allows near real-time, essentially simultaneous, surveillance of several critical sites in the porous network and facilitates selective recording and compilation of observations as a function of the biological activity at each particular site. Biofilm biomass distribution in space and time (morphology and morphological changes) are thereby recorded at a representative selection of sites in the porous structure. Local in-pore flow velocity measurements were carried out by measuring the velocity of suspended particulate matter such as detached cells or clusters of cells. The influence of biofilm morphology onconvective mass transport could thereby be observed and recorded. This effect, on a meso scale, was also monitored by sensitive, automated pressure drop measurements across the porous medium cell. Importantobservations so far include: Bioweb; the biofilm morphology in porous me [ABSTRACT FROM AUTHOR]

Hydrothermal pretreatment (HTP) (Hot water extraction (HWE) and steam pretreatment) and pyrolysis have the potential to liquefy lignocellulosic biomass. HTP produces hydrolysate, consisting mainly of solubilized hemicellulose, while pyrolysis produces aqueous pyrolysis liquid (APL). The liquid products, either as main products or by-product, can be used as anaerobic digestion (AD) feeds, overcoming shortcomings of solid-state AD (SS-AD). This paper reviews HWE, steam pretreatment, and pyrolysis pretreatment methods used to liquefy lignocellulosic biomass, AD of liquefied products, effects of inhibition from intermediate by-products such as furan and phenolic compounds, and pretreatment tuning to increase methane yield. HTP, focusing on methane production, produces less inhibitory compounds when carried out at moderate temperatures. APL is a challenging feed for AD due to its complexity, including various inhibitory substances. Pre-treatment of biomass before pyrolysis, adaptation of microorganism to inhibitors, and additives, such as biochar, may help the AD cultures cope with inhibitors in APL., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Several series of batch and continuous experiments were performed to investigate the removal of metformin and other contaminants from two wastewaters: wastewater I (WWI) containing 4 mg/L metformin and wastewater II (WWII) containing 110 g/L butanol. Biomethane potential (BMP) tests on WWII showed 77% of total chemical oxygen demand (tCOD = 110 g/L) degradability, and no apparent inhibition effects were observed. BMP tests on WWI showed an apparent inhibitory effect reflected in lower biogas production with increasing metformin concentration in the wastewater. Continuous flow hybrid vertical anaerobic biofilm (HyVAB ® ) experiments were consistent with the batch test findings. It was necessary to co-digest WWI (metformin) with WWII (easily degradable organics) to achieve complete metformin removal. After a period of adaptation, WWI and WWII co-digestion achieved up to 98% tCOD removal and 100% metformin removal. Most of the contaminants were removed in the anaerobic section of the HyVAB ® , which implies that higher chemical oxygen demand (COD) loads than tested here are possible, given some optimization. The pilot reactor was able to manage organic loads of 11 g COD/d and above 10 mg/L metformin with a removal of 98% and 100% for tCOD and metformin, respectively.

Settling velocity and size distribution of anaerobic granular sludge samples were studied using microscopic image analysis and settling column experiments. Five granule samples were considered in this study. Three samples were collected at the Top, Middle and Bottom sections of a lab scale upflow anaerobic sludge bed reactor (UASB). Two other granule samples were obtained from industries. This paper aims to establish a method that uses microscopic image analysis and shape factor as a tool to determine the size distribution and settling velocity of anaerobic granules. Image analysis technique was used to calculate the shape factor and equivalent diameter of granules. The equivalent diameter was then used to calculate the theoretical settling velocities based on Allen's formula and estimate size distributions. The results showed that there was a good agreement between the theoretical and experimental mean settling velocity values. Both measured and calculated settling velocities increased with increasing Reynolds number (Re). However, the agreement between measured and calculated values was found to be weaker at higher Re values. Size distribution analyses of the granules have revealed that there was significant difference in the size distribution of granule samples collected at different heights of the lab scale reactor. Overall, granules from the bottom section of the reactor had larger diameter, settling velocity and shape factor than those at the middle and top section granules. Whereas granules collected from the top section exhibited the smallest granular diameter, settling velocity and shape factor., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The performance of a sludge blanket anaerobic baffled reactor was tested as an integrated treatment system for source-separated blackwater. The system consists of a stirred equalization tank, a buffer inlet tank, and two identical reactors, each with a working volume of 16.4 L, operated in parallel. Both reactors run at 3-days hydraulic retention time with different intermittent pulse feeding. Pulse lengths of 12 and 24 seconds per feed were set with respective rates of 114 L h -1 and 52 L h -1 for the short-pulse fed reactor (RI) and the long-pulse fed reactor (RII). Stable performance of the reactors was attained after 120 and 90 days, for RI and RII, respectively. After stable conditions attained, total chemical oxygen demand (COD) removal efficiency stabilized above 78%. Biogas production ranged from 0.52 to 1.16 L d -1 L -1 reactor volume, with 67-82% methane concentration and an average conversion of 0.69 ± 0.2 and 0.73 ± 0.2 g CH 4 -COD g -1 COD in for RI and RII, respectively. The results imply that source-separated blackwater can be treated effectively in an anaerobic sludge blanket process on average loading rate of 2.3 ± 0.5 g COD d -1 L -1 reactor volume with high methane production potential and more than 80% removal of organic and particulate matter.

In upflow anaerobic sludge bed (UASB) reactors, biomass present as granules allows for long solids retention time. Here, granules from a process treating pulp and paper industrial wastewater were successfully applied as inoculum in UASB reactors treating pig manure supernatant, despite high particle content and high ammonium concentrations in the influent. We did a detailed characterization of archaeal and bacterial communities associated with the inoculum and with the aggregated and dispersed fractions of the influent and the reactors after one year of operation. The granular communities underwent major changes and adapted to the highly distinct conditions without disintegration of the granules. Although the granules persisted in the reactors, non-granular aggregates accumulated, and partly replaced the granules. Particles introduced to the reactors by the pig manure influent apparently contributed both as food and biofilm growth support. Archaeal communities in the dispersed reactor phase were similar to those dispersed in the influents, implying successful retention and little loss of archaeal biomass due to detachment or disintegration of granules and other aggregates. Unique bacterial communities developed in the dispersed fraction of the reactors despite of low hydraulic retention times. They probably consisted of fast growing organisms consuming readily degradable organic matter.

We examined the effect of ammonium and temperature on methane production in high rate upflow anaerobic sludge bed reactors treating pig manure supernatant. We operated four reactors at two ammonium concentrations ('low' at 1.9, 'high' at 3.7 g L -1 , termed LA and HA reactors, respectively) and at variable temperatures over 358 days. Archaeal and bacterial communities were characterized by Illumina sequencing of 16S rRNA amplicons. Ammonium was a major selective factor for bacterial and archaeal community structure. After ~200 days of adaptation to high ammonium levels, acetate and propionate removal and methane production improved substantially in HA reactors. Aceticlastic Methanosaeta was abundant and positively correlated to methane yield in the HA reactors, whereas Methanosarcina was more abundant in LA reactors. Furthermore, a group of monophyletic OTUs that was related to Thaumarchaeota in phylogenetic analysis was highly abundant in the archaeal communities, particularly in the HA reactors. The most abundant bacterial OTU in LA reactors, representing Syntrophomonadaceae, was also positively correlated to methane yield in the HA reactors, indicating its importance in methane production under ammonia stress. In conclusion, efficient methane production, involving aceticlastic methanogenesis by Methanosaeta took place in the reactors at free ammonia concentrations as high as 1 g L -1 .

The simultaneous removal of NO 3 - and HS - at temperature stress (25-10°C) is evaluated here. An expanded granular sludge bed (EGSB) reactor was run over 120days at N/S molar ratio of 0.35 (for S 0 production) under constant sulfur loading rate of 0.4kgS/m 3 d. The simultaneous removal of NO 3 - and HS - , was achieved at applied conditions. Average HS - -S removal varied from 98 (25°C) to 89.2% at 10°C, with almost complete NO 3 - removal. Average S 0 yield ranged from 83.7 at 25°C to 67% at 10°C. The temperature drop caused a decrease in granular sludge accumulated S 0 fraction by nearly 2.5 times. Decreased temperature caused metabolic pathway change observed as higher SO 4 2- production, apparently allowing the biomass to obtain more energy per HS - consumed. It is hypothesized that the metabolic shift is a natural response to compensate for temperature-induced changes in energy requirements., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Mass produced plastic syringes may be applied as vessels for cheap, simple and large scale batch culture testing. As illustrated for the cases of denitrification and of biogas formation, metabolic activity was monitored by direct reading of the piston movement due to the gas volume formed. Pressure buildup due to friction was shown to be moderate. A piston pull and slide back routine can be applied before recording gas volume to minimize experimental errors due to friction. Inoculum handling and activity may be conveniently standardized as illustrated by applying biofilm carriers. A robust set of positive as well as negative controls ("blanks") should be included to ensure quality of the actual testing. The denitrification test showed saturation response at increasing amounts of inoculum in the form of adapted moving bed biofilm reactor (MBBR) carriers, with well correlated nitrate consumption vs. gas volume formed. As shown, the denitrification test efficiently screened different inocula at standardized substrates. Also, different substrates were successfully screened and compared at standardized inocula. The biogas potential test showed efficient screening of different substrates with effects of relative amounts of carbohydrate, protein, fat. A second case with CO 2 capture reclaimer waste as substrate demonstrated successful use of co-feeding to support waste treatment and how temperature effects on kinetics and stoichiometry can be observed. In total, syringe test screening of microbial gas production seems highly efficient at a low cost when properly applied., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Sulphides are present in many wastewater streams; their removal is important due to corrosiveness, toxicity and unpleasant odour, and can be carried out by anaerobic biological treatment. This study focuses on the temperature effect (25-10 °C) on an expanded granular sludge bed (EGSB) reactor for sulphide removal using nitrate as electron acceptor. The reactor was run at a NO 3 - /HS - molar ratio of 0.35 and pH of 8.5-9.0. Samples were analysed by ion chromatography (NO 3 - , SO 4 2- and S 2 O 3 2- ), spectrophotometry (S 2- ) and by scanning electron microscopy (SEM). S 2- and NO 3 - removal was 99.74 ± 0.04 and 99.5 ± 2.9%, respectively. Sulphur (S 0 ) was found on the outer granule surface and struvite inside the granule, by SEM. Sulphide conversion to sulphur was up to 76%. Temperature transitions and levels influenced S 2 O 3 2- and SO 4 2- concentrations.

The study shows that high rate anaerobic digestion may be an efficient way to obtain sustainable energy recovery from slurries such as pig manure. High process capacity and robustness to 5% daily load increases are observed in the 370 mL sludge bed AD reactors investigated. The supernatant from partly settled, stored pig manure was fed at rates giving hydraulic retention times, HRT, gradually decreased from 42 to 1.7 h imposing a maximum organic load of 400 g COD L(-1) reactor d(-1). The reactors reached a biogas production rate of 97 g COD L(-1) reactor d(-1) at the highest load at which process stress signs were apparent. The yield was ∼0.47 g COD methane g(-1) CODT feed at HRT above 17 h, gradually decreasing to 0.24 at the lowest HRT (0.166 NL CH4 g(-1) CODT feed decreasing to 0.086). Reactor pH was innately stable at 8.0 ± 0.1 at all HRTs with alkalinity between 9 and 11 g L(-1). The first stress symptom occurred as reduced methane yield when HRT dropped below 17 h. When HRT dropped below 4 h the propionate removal stopped. The yield from acetate removal was constant at 0.17 g COD acetate removed per g CODT substrate. This robust methanogenesis implies that pig manure supernatant, and probably other similar slurries, can be digested for methane production in compact and effective sludge bed reactors. Denaturing gradient gel electrophoresis (DGGE) analysis indicated a relatively fast adaptation of the microbial communities to manure and implies that non-adapted granular sludge can be used to start such sludge bed bioreactors., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

An aerobic dynamic discharge (ADD) process involving physical selective pressure to favor the accumulation of polyhydroxyalkanoates (PHAs) accumulating bacteria in microbial mixed cultures (MMCs) is proposed and evaluated in this study. Sequencing batch reactor PHA production in the ADD mode was compared to the conventional aerobic dynamic feeding (ADF) mode. Results showed that the cultures selected under the ADD mode showed a better PHA producing potential than ADF mode cultures in terms of both maximum PHA content and selection time, explained by altered physical selective pressure. The maximum PHA content of 74.16 (± 0.03)% and PHA yield of 0.72 (± 0.07) C mol PHA/C mol Ac were achieved after 30 days of the ADD operation, which were much higher than those obtained under the same organic loading rate in the ADF operation. The ADD mode is a promising method for quick selection of a strong-PHA accumulating culture., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Performance of a 250 L pilot-scale up-flow anaerobic sludge blanket (UASB) reactor, operated at ambient temperatures, fed septic tank effluents intermittently, was monitored for hydraulic retention time (HRT) from 18 h to 4 h. The total suspended solids (TSS), total chemical oxygen demand (CODT), dissolved chemical oxygen demand (CODdis) and suspended chemical oxygen demand (CODss) removal efficiencies ranged from 20 to 63%, 15 to 56%, 8 to 35% and 22 to 72%, respectively, for the HRT range tested. Above 60% TSS and 47% CODT removal were obtained in the combined septic tank and UASB process. The process established stable UASB treatment at HRT≥6 h, indicating a hydraulic load design limit. The tested septic tank-UASB combined system can be a low-cost and effective on-site sanitation solution.

Three laboratory-scale septic tanks, an anaerobic baffled reactor (ABR)-septic tank (R1), a Yuhuan drawing three-dimensional-carrier-septic tank (R2) and a conventional septic tank (R3), were operated in parallel over half a year under hydraulic retention times (HRTs) of 36, 24 and 12 h, with a sewage temperature of 16 degrees C. The removal efficiencies of total chemical oxygen demand (CODtot) achieved in R1 and R2 increased by 14%, 21% and 12% and 18%, 3% and 16%, respectively, under three different HRTs, as compared to those in R3. The total nitrogen and phosphorus removal efficiencies were negligible. R1 sludges had a higher specific methane production rate as compared to that of R2 and R3 sludges. The results indicated that the two modified septic tanks can improve the performance in terms of COD and total solids removal, both were suitable technologies for domestic sewage (pre) treatment at low temperature in northern China.