Anaerobic Zone Research Articles

Limnological Conditions and Photosynthetic Pigments in Clearwater Lakes of the Volga-Vyatka Karst Province

The features of summer stratification and vertical distribution of photosynthetic pigments (chlorophylls and bacteriochlorophylls) in five karst lakes in the Middle Volga region (Republics of Tatarstan and Mari-El) are studied. The water of the investigated lakes has low color and sulfate concentration and low-to-medium total dissolved salts content. Anoxic conditions develop in the hypolimnion in all lakes after the establishment of summer thermal stratification. Reduced iron and sulfur compounds are found in the anaerobic zones of most lakes. In these lakes, deep maxima of chlorophyll and bacteriochlorophylls are formed, indicating the presence of biomass maxima of microbial plankton, consisting of both oxygenic and anoxygenic phototrophs. The presented data demonstrate also a wide variety of features of both chemical stratification and vertical distribution of phototrophic organisms in the studied lakes, which are probably associated with differences in the limnological characteristics of lakes, their water composition, and the history of their existence.

Role of air scouring in anaerobic/anoxic tanks providing nitrogen removal by mainstream anammox conversion in a hybrid biofilm/suspended growth full-scale WWTP in China.

A full-scale wastewater treatment plant in China experienced unintentional anammox bacterial enrichment on biofilm carriers placed in the anaerobic and anoxic zones of an anaerobic/anoxic/oxic process under ambient temperatures and without bioaugmentation. Here, we show that microaerophilic conditions resulting from air scouring needed for biofilm carrier suspension in the anaerobic/anoxic zones can support a robust nitritation/anammox process. Results from an in situ on/off air scouring test showed that air scouring strongly induced both ammonia and total inorganic nitrogen removal in the anaerobic/anoxic zones. Ammonium concentration in the anaerobic and anoxic tanks remained constant or even slightly increased when air scouring was off, indicating that air scouring made a noticeable difference in nitrogen profiles in the anaerobic/anoxic zones. Various batch tests further indicated that partial denitrification is not likely to generate nitrite for anammox bacteria. Robust nitritation, and anammox on the carriers, can occur at low dissolved oxygen conditions, as measured in the full-scale facility. The observations show that mainstream deammonification without sidestream bioaugmentation at moderate temperature is feasible and further optimization by a more dedicated design can result in improved nitrogen removal in cases when chemical oxygen demand is limited in mainstream wastewater treatment. PRACTITIONER POINTS: Microaerophilic conditions in a full-scale IFAS reactor caused mainstream anammox in moderate temperate area. Robust nitritation, and anammox on the carriers, can occur at low dissolved oxygen conditions in anaerobic/anoxic tanks with air scouring. Anammox can function well with conventional nitrification and denitrification process at mainstream conditions for stable nitrogen removal.

Enhancing the treatment of petrochemical wastewater using redox mediator suspended biofilm carriers

The treatment efficiency of petrochemical wastewater via the traditional activated sludge process is generally unsatisfactory due to the complex and toxic features of petroleum compounds. Redox mediator (RM) can improve the biodegradation of organic contaminants by participating in the microbial extracellular electron transfer process. However, the continuous dosing of the soluble redox mediator would lead to secondary pollution and rise operation cost. In this study, an insoluble and economical redox mediator material (biochar) was introduced into high-density polyethylene (HDPE) to prepare suspended biofilm carriers (RM-modified carriers), and applied in anaerobic/oxic (A/O) reactors. The reactor filled with RM-modified carriers (R3) showed the removal efficiency of chemical oxygen demand (COD) and phenol in the anaerobic zone were 34.6 % and 43.0 % respectively at organic loading rates (OLRs) of 22.2 kg COD/(m3·d), which increased by 6.8 % and 8.3 % respectively compared with that of the reactor filled with conventional HDPE carriers (R2), and increased by 12.4 % and 17.7 % respectively compared with that of the reactor without filled with carriers (R1). Microbial analysis proved that the relative abundance of Bacteroides that participated in electron transfer of R3 improved by approximately 6.3 % compared with that of R2. These findings demonstrated that RM-modified carriers improved the abundance of relevant functional bacteria and enhanced the degradation efficiency of the contaminants in petrochemical wastewater.

Partial nitrification coupled with denitrification and anammox to treat landfill leachate in a tower biofilter reactor (TBFR)

This study investigated the performance of partial nitrification (PN), carbon oxidation, denitrification and anammox in a continuous tower biofilter reactor (TBFR) with large height-to-diameter ratio of 13 in treating actual landfill leachate. The nitrogen loading rate (NLR) and organic loading rate (OLR) varied from 0.44 to 1.31 kg-N/(m3·day) and 1.59 to 4.76 kg/(m3·day), respectively. The average removal rates of total nitrogen (TN) and chemical oxygen demand (COD) in the TBFR reached 87.47% and 88.45% at the maximum NLR and OLR of 1.31 kg-N/(m3·day) and 4.76 kg/(m3·day), respectively. Variation of water quality along the TBFR in different operating conditions indicated that approximately 45% - 60% of the influent NH4+-N was converted into NO2−-N, and nearly 55% - 70% of the influent COD was removed in the 0–40 cm zone, which provided suitable conditions for the subsequent anaerobic anammox and denitrification processes in the 40–160 cm zone. Overall, the TBFR with a large height-to-diameter ratio demonstrated an effective technology for the treatment of landfill leachate by creating distinct aerobic and anaerobic zones in a single reactor.

The influence of sulphate on the treatment of azo dye‐containing wastewater in an anaerobic‐microaerobic compartmentalized fixed‐bed bioreactor

AbstractA fixed bed reactor (FBR) comprised of an anaerobic zone (AZ) coupled to a micro‐aerated zone (MAZ) was used for the biological treatment of synthetic textile wastewater. The azo dye in the textile effluent is expected to be reduced to aromatic amines (decolouration) in AZ followed by biological degradation of the aromatic amines due to oxygen exposure in MAZ. We focused on assessing the effect of sulphate, a common component of textile wastewaters, on the degradation of the tetra‐azo dye Direct Black 22 (DB22). The influence of sulphide, a product of sulphate biological reduction, on the removal of aromatic amines, toxic by‐products of DB22 degradation, was also analyzed. The AZ and the MAZ were filled with expanded clay balls and polyurethane foam, respectively. The chemical oxygen demand and sulphate ratio (COD/SO4−2) in the feed started at 4.8 ± 0.2 and was later changed to 0.8 ± 0.1 by increasing the sulphate content. This change consequently increased DB22 removal efficiency from 38 ± 11% to 72 ± 6% in AZ and from 56 ± 7% to 75 ± 7% at MAZ, but also resulted in high sulphide concentration and reduced redox potential (ORP) at the MAZ inlet. However, the change negatively affected the degradation of aromatic amines in the MAZ. Aromatic amines were removed only at redox potential values higher than −228 mV and biogenic sulphide concentrations lower than 44 mg HS−/L.

Effects of black carbon-based thin-layer capping for nitrogen-overloaded sediment remediation on microbial community assembly

Black carbon is considered as a promising material for thin-layer capping for sediment remediation. However, the effects of black carbon-based thin-layer capping on microbial communities have not been thoroughly studied. Here, the preparation conditions of capping material were optimized, and the interaction and assembly mechanisms of the microbial community in sediment under black carbon capping were studied. The results showed that concentration of NH4+-N in the overlying water was stably lower than 0.5 mg/L after capping. The abundance of key genes related to nitrogen transformation in the sediment was increased. Denitrification was the dominant nitrogen removal pathway under coarse granule capping, while aromatic compound degradation was dominant under fine granule capping and dissimilatory N reduction to ammonium was regarded as the dominant nitrogen removal pathway. Community assembly was mainly driven by deterministic processes (≥ 80%). Interactions between rare and common operational taxonomic units were most frequent. The functional zoning of nitrogen transformation in the vertical aerobic, hypoxic, and anaerobic zones of the sediment was strengthened because of black carbon capping. Overall, these results expand our current understanding of the ecological significance of black carbon capping for remediating contaminated sediment.

Hacking biofilm developed in a structured-bed reactor (SBRRIA) with integrated processes of nitrogen and organic matter removal.

Biomass samples from a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) were analyzed to investigate the bacterial community shift along with the changes in the C/N ratio. The C/N ratios tested were 7.6 ± 1.0 (LNC) and 2.9 ± 0.4 (HNC). The massive sequencing analyses revealed that the microbial community adjusted itself to different organic and nitrogenous applied loads, with no harm to reactor performance regarding COD and Total-N removal. Under LNC, conventional nitrification and heterotrophic denitrification steered the process, as indicated by the detection of microorganisms affiliated with Nitrosomonadaceae, Nitrospiraceae, and Rhodocyclaceae families. However, under HNC, the C/N ratio strongly affected the microbial community, resulting in the prevalence of members of Saprospiraceae, Chitinophagaceae, Xanthomonadaceae, Comamonadaceae, Bacillaceae, and Planctomycetaceae. These families include bacteria capable of using organic matter derived from cell lysis, ammonia-oxidizers under low DO, heterotrophic nitrifiers-aerobic denitrifiers, and non-isolated strains of Anammox. The DO profile confirmed that the stratification in aerobic, anoxic, and anaerobic zones enabled the establishment of different nitrogen degradation pathways, including the Anammox.

Mitigation of methane and trace gas emissions through a large-scale active biofilter system at Glatved landfill, Denmark

Biocover systems are a cost-effective technology utilised to mitigate methane (CH4) and trace gas emissions from landfills. A full-scale biofilter system was constructed at Glatved landfill, Denmark, consisting of three biofilters with a total area of 3950 m2. Landfill gas collected mainly from shredder waste cells was mixed with ambient air and fed actively into the biofilter, resulting in an average load of 60–75 g m−2 d−1 for CH4 and 0.15–0.21 g m−2 d−1 for trace gases (e.g., aromatics, chlorofluorocarbons (CFCs), aliphatic hydrocarbons). The initial CH4 surface screening showed uneven gas distribution into the system, and elevated surface concentrations were observed close to the gas inlet. Both positive and negative CH4 fluxes, ranging from −0.36 to 4.25 g m−2 d−1, were measured across the surface of the biofilter. Total trace gas emissions were between −0.005 and 0.042 g m−2 d−1, and the emission flux of individual compounds were generally small (10−8 to 10−3 g m−2 d−1). Vertical gas concentration profiles showed that the oxidation of CH4 and easily degradable trace compounds such as aromatics and aliphatic hydrocarbons happened in the aerobic zones, while CFCs were degraded in the anaerobic zone inside the compost layer. In addition, oxidation/degradation of CH4 and trace gases also occurred in the gas distribution layer, which contributed significantly to the overall mitigation efficiency of the biofilter system. Overall, the biofilter system showed mitigation efficiencies of nearly 100% for both CH4 and trace gases, and it might have the potential to work under higher loads.

Effects of anaerobic HRT and VFA loading on the kinetics and stoichiometry of enhanced biological phosphorus removal

Enhanced biological phosphorus removal (EBPR) can recover significant quantities of wastewater phosphorus. However, this resource recovery process realizes limited use largely due to process stability concerns. Research evaluated effects of anaerobic HRT (τAN ) and VFA concentration - critical operational parameters that can be externally controlled - on EBPR performance. Evaluated alone, τAN (1-4 hours) exhibited no statistical effect on effluent phosphorus. However, PHA increased with VFA loading and biomass accumulated more phosphorus. Regarding resiliency, under increasing VFA loads PAOs hydrolyzed more phosphorus to uptake/catabolize VFAs; moreover, PHA synthesis normalized to VFA loading increased with τAN , suggesting fermentation. Kinetically, PAOs exhibited Monod-like relationships for qPHAAN and qVFAAN as a function of anaerobic P release; additionally, qPAE exhibited a Monod-like relationship with end-anaerobic PHA concentration. A culminating analysis affirmed the relationship between enhanced aerobic P uptake, and net P removal, with a parameter (Phosphorus Removal Propensity Factor) that combines influent VFA concentration with τAN .

The microbiome of the Black Sea water column analyzed by shotgun and genome centric metagenomics

BackgroundThe Black Sea is the largest brackish water body in the world, although it is connected to the Mediterranean Sea and presents an upper water layer similar to some regions of the former, albeit with lower salinity and temperature. Despite its well-known hydrology and physicochemical features, this enormous water mass remains poorly studied at the microbial genomics level.ResultsWe have sampled its different water masses and analyzed the microbiome by shotgun and genome-resolved metagenomics, generating a large number of metagenome-assembled genomes (MAGs) from them. We found various similarities with previously described Black Sea metagenomic datasets, that show remarkable stability in its microbiome. Our datasets are also comparable to other marine anoxic water columns like the Cariaco Basin. The oxic zone resembles to standard marine (e.g. Mediterranean) photic zones, with Cyanobacteria (Synechococcus but a conspicuously absent Prochlorococcus), and photoheterotrophs domination (largely again with marine relatives). The chemocline presents very different characteristics from the oxic surface with many examples of chemolithotrophic metabolism (Thioglobus) and facultatively anaerobic microbes. The euxinic anaerobic zone presents, as expected, features in common with the bottom of meromictic lakes with a massive dominance of sulfate reduction as energy-generating metabolism, a few (but detectable) methanogenesis marker genes, and a large number of “dark matter” streamlined genomes of largely unpredictable ecology.ConclusionsThe Black Sea oxic zone presents many similarities to the global ocean while the redoxcline and euxinic water masses have similarities to other similar aquatic environments of marine (Cariaco Basin or other Black Sea regions) or freshwater (meromictic monimolimnion strata) origin. The MAG collection represents very well the different types of metabolisms expected in this kind of environment. We are adding critical information about this unique and important ecosystem and its microbiome.

Vivianite scaling in wastewater treatment plants: Occurrence, formation mechanisms and mitigation solutions

The presence of soluble iron and phosphorus in wastewater sludge can lead to vivianite scaling. This problem is not often reported in literature, most likely due to the difficult identification and quantification of this mineral. It is usually present as a hard and blue deposit that can also be brown or black depending on its composition and location. From samples and information gathered in 14 wastewater treatment plants worldwide, it became clear that vivianite scaling is common and can cause operational issues. Vivianite scaling mainly occurred in 3 zones, for which formation hypotheses were discussed. Firstly, iron reduction seems to be the trigger for scaling in anaerobic zones like sludge pipes, mainly after sludge thickening. Secondly, pH increase was evaluated to be the major cause for the formation of a mixed scaling (a majority of oxidized vivianite with some iron hydroxides) around dewatering centrifuges of undigested sludge. Thirdly, the temperature dependence of vivianite solubility appears to be the driver for vivianite deposition in heat exchanger around mesophilic digesters (37 °C), while higher temperatures potentially aggravate the phenomenon, for instance in thermophilic digesters. Mitigation solutions like the use of buffer tanks or steam injections are discussed. Finally, best practices for safe mixing of sludges with each other are proposed, since poor admixing can contribute to scaling aggravation. The relevance of this study lays in the occurrence of ironphosphate scaling, while the use of iron coagulants will probably increase in the future to meet more stringent phosphorus discharge limits.

Bacterial community responses to the redox profile changes of mariculture sediment

Suspended mariculture has significantly influences on the benthic sediment. However, our understanding on how bacterial communities respond to mariculture induced changes in redox profiles is limited. In present study, sediments from two maricultures and reference areas were collected and incubated for 28 day. The results indicated that the dominant pathway of organic matter mineralization in the sediment varied from groups, in the reference, it was the iron reduction, but in the two mariculture groups it was the SO42− reduction. Remarkable changes of bacteria community were recorded in the aerobic zone, where the abundances of 14 OTUs belonging to Gammaproteobacteria and Alphaproteobacteria were significantly higher than that in oxidation and anaerobic zones. However, 4 keystone OTUs were strictly anaerobic and belonging to Desulfobacteraceae (n = 3) and Marinilabiaceae (n = 1). The main environmental drivers determining sediment bacterial distribution were the particle organic carbon, dissolve oxygen, NO3−, and moisture content.

High-rate CNP removal from wastewater in a single jet loop air lift bioreactor: Process modeling and optimization with four process and operating factors

The present study investigates a jet loop-air lift bioreactor employed as a single cost-effective system with anaerobic, aerobic and anoxic zones in order to achieve high-rate simultaneous CNP removal from soft drink wastewater. The reactor was operated at continuous regime while different conditions were designed using central composite design (CCD) under response surface methodology. Four independent variables including hydraulic retention time (HRT), anaerobic volume to total working volume ratio (VAn/VT), air flow rate (AFR), and influent nitrogen concentration in the range of 8−16 h, 0.04−0.12, 3.5–5.5 l/min, and 150−300 mg/l, respectively, were evaluated in terms of their impacts on several responses. With regards to the results obtained, HRT and AFR directly enhanced the biological CNP removal while a decreasing effect for VAn/VT was observed. COD and TP removal efficiencies were not affected by influent nitrogen concentration while TN removal efficiency was negatively affected. Overall, chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) removal efficiencies obtained at optimum conditions (HRT: 14 h, VAn/VT: 0.06, AFR: 5.5 L/min, and influent nitrogen: 225 mg/l) were 97 %, 63 %, and 81 %, respectively, proving the reactor’s potential to remove CNP efficiently. The maximum COD, TN, TP removal efficiencies were 97, 99.9, 81 %, respectively.

Technology for biological treatment of urban wastewater and sludge treatment with deep removal of nitrogen and phosphorus

This article is dedicated to increasing of removing of nitrogen and phosphorus in DENIFO technology, and the removing of phosphorus by reagents. Removal of nitrogen and phosphorus from municipal wastewater prevents eutrophication of open water, which has become a global problem. A list of conditions that provide maximum efficiency of the processes of wastewater treatment and sludge treatment is completed. Functions of primary settlers, air tanks (based on technology DENIFO), and secondary settlers is reviewed. Pre-denitrification of the returned active sludge with the partial flow of waste water improves anaerobiosis in the anaerobic zone of biological block, and promotes intensive dephosphorization. The work was made under normal conditions of wastewater treatment plant. Unfavorable periods (snowmelt, torrential rains, floods) are not taken into consideration. Mathematical equations are made for the average flow of wastewater during dry weather. Combined dehydratation of the sludge and sediments (the long stay in the tank) leads to rapid displacement phosphorus phosphate to drain water, and a corresponded increase the content of phosphorus in the treated water. Also recommendations for changing the operating mode of the block of sludge treatment given. The important results included in article was taken on the really functioned wastewater treatment plants of Saint Petersburg. This work is aimed at a comprehensive assessment, development and improvement of technology of removing nitrogen and phosphorus from municipal wastewater, including from secondary pollution coming from the return flow from the sludge treatment units.

Biofilm development in a pilot-scale gravity sewer: Physical characteristics, microstructure, and microbial communities

The existence of abundant biofilms on sewer pipeline walls can lead to negative environmental impacts, such as poisonous gas release and pipe corrosions through transforming various pollutants. Investigating the formation process of sewer biofilms is of importance in advancing knowledge of sewer operation and maintenance. In this study, the changes in physical characteristics, microstructure, and microbial communities of sewer biofilm were analyzed in-depth in a pilot-scale gravity sewer during a 45-day operation. The results show that a high specific surface area at the early stage could channel the substrates for stimulating the primary colonizers (e.g., Cytophagia, Sphingobacteriia, Alpha-, and Betaproteobacteria), which could excrete an extracellular matrix to facilitate biofilm growth. The sewer biofilms were gradually formed with 62 g VS/m2 organic content, 1.2 mm biofilm thickness, and 89 mg/cm3 dry density after 45 days operation. Moreover, the biofilm growth promoted the emergence of facultative bacteria and anaerobes (affiliated with Flavobacteriia, Gemmatimonadetes, Deltaproteobacteria, and Epsilonproteobacteria). Microelectrode analysis further verified that an anaerobic zone existed in mature biofilm with a negative oxidation-reduction potential (−105 mV), where approximately 0.1 μmol/L of sulfide was produced. Our results suggest that the migration of the microbial community correlated with the changes in the evolved physical characteristics and microstructure of sewer biofilm, and this can contribute to the strategies for sulfide control for improving sewer maintenance.

Peculiarities of respiratory functions in qualified swimmers exposed to multidirectional physical loads

The peculiarities of the swimmers’ respiratory system response to a special physical load were studied. The swimmers of high sports qualification aged 16–18 years old, who specialize in swimming at distances of various lengths, underwent the examination. At the first stage, we used exercises aimed at enhancing the anaerobic work power in swimming. At the second stage, the parameters of the swimmers’ respiratory system response to the load in aerobic and anaerobic zone were studied. At the third stage of the study, the changes of the swimmers’ respiratory functions under physical loads at the level of MOC (maximum oxygen consumption) were researched. The investigation of respiratory system functions of stayer swimmers was conducted with the use of a Spirolab-3 spirometer (spirograph). We found that the recovery of qualified swimmers can be activated when aerobic and anaerobic mechanisms of energy metabolism are combined. The results of the study confirm that the swimmers’ respiratory functions influence the processes of recovery of their working capacity after being exposed to multidirectional physical loads. The sprinters’ anaerobic mechanisms of muscle function are better developed. The stayers’ aerobic mechanisms of energy metabolism function better. In order to activate the recovery of qualified swimmers, it is advisable to combine aerobic and anaerobic mechanisms of energy metabolism.

Climate Change as an Important Factor of the Formation of the Chemical Composition of Surface Waters at the Present Time (a Review)

Results of the study of climate change impact on the chemical composition of surface waters given in literature have been generalized in the paper. It has been shown that climate change influences mainly hydrologic, chemical, and biological processes occurring in water bodies and watercourses. Climate change can result in change in river runoff and in water level in lakes, reservoirs, and limans. The increase in water temperature can result in time displacement and in the increase in the duration of temperature stratification in lake systems. Shallow lakes are most vulnerable to climate change. Temperature stratification in lakes and reservoirs is accompanied by oxygen stratification. As a consequence, the water of hypolimnion is characterized by prolonged dissolved oxygen deficiency, and also by the formation of anaerobic zones. Under such conditions, the intensity of nutrients and organic matter migration from bottom sediments into water column will increase. This process will be accompanied by the increase in the degree of eutrophication of water bodies, in particular by the increase in the intensity of phytoplankton development. Climate change influences salt composition of surface waters and relationship between its main components. It will result in the increase in the concentration of allochthonous organic matter (in particular of humic acids) as a result of its influx from the bottom sediments of swamps with increasing the amount of precipitation, and also in the increase in the concentration of autochthonous organic matter as a result of the increase in bioproductivity of water bodies. Prolonged solar radiation in summertime will favor the increase in the intensity of photochemical reactions in water bodies, which will manifest itself in transformation of high molecular organic matter into the compounds with lower molecular mass. Other aspects of climate change impact on the chemical composition of surface waters are also discussed in the paper.

Influence of Body Composition Parameters on Anaerobic Strength of Lower Extremities in Female Football Players

The aim of this study was to investigate the influence of body composition on the anaerobic strength of the lower extremities, as well as the prediction of body composition on the results of anaerobic ability in professional football players. Materials and Method. The sample of respondents consists of female football players who compete in the highest rank of the competition, the Serbian Super League. The total number of respondents included in the study was 21 female football players (age 19.38 ± 3.69, body height 166.48 ± 6.17 cm, body weight 59.98 ± 7.09 kg). The study is of a transversal nature and testing was done in the pre-competition period. The sample of measuring instruments used in the research are body composition and assessment of anaerobic strength of the lower extremities. Assessment of body composition was performed indoors using a multifrequency bioelectric impedance (Inbody 770). Variables for estimating the anaerobic strength of the lower extremities were obtained using a bicycle ergometer (Monark 839E) in the Wingate Anaerobic Test. Results. The results of body composition show a statistically significant influence on the prediction of maximum anaerobic strength of the lower extremities in professional female football players (p < 0.05), as well as on the overall work in the anaerobic zone and the mean values ​​of anaerobic strength. Regression analysis of the influence of body composition on the parameters of maximum strength in (W/kg) and fatigue rate does not show statistically significant results. Conclusion. There is a statistically significant influence of body composition, such as: body weight, lean body mass (%), muscle mass in absolute and relative values, on the values ​​of maximum anaerobic strength, mean values ​​of anaerobic strength and overall work in professional female footballers.

New Frontiers of Anaerobic Hydrocarbon Biodegradation in the Multi-Omics Era.

The accumulation of petroleum hydrocarbons in the environment substantially endangers terrestrial and aquatic ecosystems. Many microbial strains have been recognized to utilize aliphatic and aromatic hydrocarbons under aerobic conditions. Nevertheless, most of these pollutants are transferred by natural processes, including rain, into the underground anaerobic zones where their degradation is much more problematic. In oxic zones, anaerobic microenvironments can be formed as a consequence of the intensive respiratory activities of (facultative) aerobic microbes. Even though aerobic bioremediation has been well-characterized over the past few decades, ample research is yet to be done in the field of anaerobic hydrocarbon biodegradation. With the emergence of high-throughput techniques, known as omics (e.g., genomics and metagenomics), the individual biodegraders, hydrocarbon-degrading microbial communities and metabolic pathways, interactions can be described at a contaminated site. Omics approaches provide the opportunity to examine single microorganisms or microbial communities at the system level and elucidate the metabolic networks, interspecies interactions during hydrocarbon mineralization. Metatranscriptomics and metaproteomics, for example, can shed light on the active genes and proteins and functional importance of the less abundant species. Moreover, novel unculturable hydrocarbon-degrading strains and enzymes can be discovered and fit into the metabolic networks of the community. Our objective is to review the anaerobic hydrocarbon biodegradation processes, the most important hydrocarbon degraders and their diverse metabolic pathways, including the use of various terminal electron acceptors and various electron transfer processes. The review primarily focuses on the achievements obtained by the current high-throughput (multi-omics) techniques which opened new perspectives in understanding the processes at the system level including the metabolic routes of individual strains, metabolic/electric interaction of the members of microbial communities. Based on the multi-omics techniques, novel metabolic blocks can be designed and used for the construction of microbial strains/consortia for efficient removal of hydrocarbons in anaerobic zones.

Nested control loop configuration for a three stage biological wastewater treatment process

Abstract In every urban infrastructure, Wastewater Treatment Plant (WWTP) requires special attention because of its adverse effects on the environment and also for resource recovery. Therefore, there arises a need to treat the wastewater in order to meet the effluent norms prior to discharge. Different control strategies and various scenarios of plant layout can be tested and evaluated through modelling and simulation studies on the benchmark layouts. In this paper, a feedforward nested loop control structure based on ammonia concentration is implemented on Benchmark Simulation Model (BSM1-P) developed based on Activated Sludge Model No. 3 bioP (ASM3bioP) for controlling the dissolved oxygen in aerobic zones and nitrate level in anoxic zones and nutrient removal by adding two anaerobic zones. By using this control strategy, pumping energy, percentage violations of ammonia and nitrogen concentrations in the effluent, and effluent quality are reduced effectively.