Addition of Trichocladium canadense to an anaerobic membrane bioreactor: evaluation of the microbial composition and reactor performance.

Membrane bioreactors are powerful systems for wastewater treatment and the removal of toxic compounds. However, membrane biofouling stands in the way of their widespread usage. In this study, the saprophytic fungus Trichocladium canadense was used as the bioaugmentor in an anaerobic membrane bioreactor (AnMBR) and its impact on membrane biofouling, biogas production, the microbial communities of the reactor and removal of the common antibiotics erythromycin (ERY), sulfamethoxazole (SMX) and tetracycline (TET) from synthetic wastewater was investigated. The results indicated that through bioaugmentation with 20% T. canadense, membrane biofouling was slowed by 25%, the chemical oxygen demand removal increased by 16% and a higher efficiency removal of ERY and SMX was achieved. The presence of T. canadense significantly increased the abundance and diversity of the biofilm archaeal community and the bacterial phylum Firmicutes, a known bio-foulant.

Anaerobic treatment of propylene glycol-contaminated domestic wastewater and microbial community profile at threshold ratio.

An up-flow anaerobic sludge bed (UASB) reactor was operated for five months to treat domestic wastewater contaminated by propylene glycol -main component of Type 2 aircraft deicing fluid (ADF)- at threshold ratio based on optimization study with batch reactors [i.e., operated at externally included ADF = 0.83-4.20%]. Biogas yields up to ~0.4 m3/kg CODinfluent was achieved, however drastically reduced along with total chemical oxygen demand (tCOD) removal at ADF>1.20% and indicated strong inhibition. Hence, the UASB reactor was fed at ADF = 1.05% [tCODinfluent = 8930 ± 2100 mg/L] and yielded >80% tCOD removal on average. Next generation sequencing (NGS) findings also revealed that Firmicutes and Bacteroidetes had the highest ratios of relative abundances in biomass sample taken at the last operating day; hence co-existence of these phyla played significant role in glycol removal with Synergistetes and Thermotogae bacteria whereas Methanobacterium and Methanoculleus archaea increased remarkably.

Comparative assessment of modeling and experimental data of ammonia removal from pre-digested chicken manure.

The aim of this study was to interpret the development of Anammox activity by a mathematical model in an UASB reactor -originally inoculated with methanogenic granules- at which Anammox progress has been also experimentally observed while treating chicken manure digestate. Since ammonium is derived from anaerobic degradation of nitrogenous compounds in chicken manure similar to any other nitrogen-rich organic wastes; the reactor was operated intentionally at favorable conditions [i.e.; with external nitrite source for NH4 +:NO2 -≅1.0] in order to make Anammox process to prevail as operation continued. Results indicated significant ammonia removals (60% on average) although influent concentration was gradually increased up to 200 mg L-1. A modeling exercise has been undertaken to investigate the performance of the laboratory scale UASB reactor. In this scope, the experimental results were modeled by using Mantis2 model within GPS-X 6.5 simulation software that included several built in libraries. Accordingly, effluent chemical oxygen demand (COD) and total ammonia nitrogen (TAN) concentrations could be predicted with reasonably good accuracy demonstrating successful calibration. The regression coefficient (R2 ) and mean relative absolute error (MRAE) parameters were found as 0.66 and 16% and 0.70 and 19%, respectively.

Impact of ultrasonic pre-treatment on domestic sludge digestion performance and microbial community dynamics.

Ultrasonication-assisted sludge digestion technology is a lately used alternative sludge treatment method in wastewater treatment plants (WWTPs). This study focused on determining the influence of ultrasonication on aerobic and anaerobic sludge digestion, two most commonly used sludge handling processes, as well as on the investigation of microbial community structure after digestion. The effect of ultrasonication as a pre-treatment technique prior to sludge digestion on microbial population dynamics was not yet investigated comprehensively. Sludge sample taken from the primary and secondary settling tanks of a domestic wastewater treatment plant was used during the experiments. Based on the relevant data, while applied ultrasonication did not improve the anaerobic digestion efficiency, progress was achieved in the sludge dewaterability characteristics at the end of aerobic digestion. According to the results of both denaturant gradient gel electrophoresis and pyrosequencing data, ultrasonic pre-treatment decreased the richness of the microbial population in aerobic digestion, whereas increased the biocomplexity of the population in anaerobic digestion. We revealed that sludge pre-treatment with ultrasonication does not always improve the digestion performance. Composition of the sludge was the main factor defining the digestion performance.

Impact of inoculum acclimation on energy recovery and investigation of microbial community changes during anaerobic digestion of the chicken manure.

The aim of this study was to assess the effect of inoculum adaptation on biogas recovery from two identical lab-scale semi-continuous anaerobic digesters (AD) treating chicken waste (i.e. TS and VS contents of ca. 6.2% and 2.9%, respectively) at mesophilic condition (35°C). For the first two months; one of the AD was run with adapted whereas the second AD was run with unadapted granular sludge to chicken manure which was further operated for about 100 more days. In this scope, qPCR analysis and Illumina sequencing were also used to detect microbial community changes inside anaerobic reactors. Molecular analyses revealed that the number of archaea was significantly higher than that of overall archaea compared to the values obtained at the start-up time and methanogens also increased as the operation continued. On the other hand, although average daily biogas production was about 25% higher in adapted AD compared to the unadapted AD (i.e. biogas yields were ca. 0.6 and 0.7 m3/kg VSfeed, respectively), there was not a meaningful change in archaea numbers at the end of the operation. These suggest that changes in the structure of a microbial community lead to changes in biogas production and controlling ultimate methanogenic archaeal community may promote successful methane production in anaerobic reactors.

Microbial monitoring of ammonia removal in a UASB reactor treating pre-digested chicken manure with anaerobic granular inoculum.

Performance and microbial community dynamics in an upflow anaerobic sludge bed (UASB) reactor coupled with anaerobic ammonium oxidizing (Anammox) treating diluted chicken manure digestate (Total ammonia nitrogen; TAN=123±10mg/L) were investigated for a 120-d operating period in the presence of anaerobic granular inoculum. Maximum TAN removal efficiency reached to above 80% with as low as 20mg/L TAN concentrations in the effluent. Moreover, total COD (tCOD) with 807±215mg/L in the influent was removed by 60-80%. High-throughput sequencing revealed that Proteobacteria, Actinobacteria, and Firmicutes were dominant phyla followed by Euryarchaeota and Bacteroidetes. The relative abundance of Planctomycetes significantly increased from 4% to 8-9% during the late days of the operation with decreased tCOD concentration, which indicated a more optimum condition to favor ammonia removal through anammox route. There was also significant association between the hzsA gene and ammonia removal in the UASB reactor.

Acute and chronic responses of denitrifying culture to diclofenac.

Acute and chronic effect as well as biodegradation potential at different sludge retention times (SRTs) of a priority pollutant, diclofenac on denitrification process was assessed. The continuous amendment of the culture for 6months with 1µg/L diclofenac resulted in 30% decrease in gas production. The average diclofenac removal observed in the diclofenac-acclimated culture was less than 15%. Batch tests showed that nitrate was removed in diclofenac free-control reactor at a higher rate compared to diclofenac amended reactor. Although, SRT did not have any progressive effect on diclofenac degradation, the system operated at low SRT was more sensitive to diclofenac and resulted in an increase in N2O emission. Wastewater treatment plants (WWTPs) operated at higher SRTs may tolerate and recover from the adverse effects of such micropollutants. The study can lead to other researchers to understand the fate and effect of other emerging pollutants in the anoxic unit of WWTPs.

Bioenergy production from diluted poultry manure and microbial consortium inside Anaerobic Sludge Bed Reactor at sub-mesophilic conditions.

In this study, anaerobic treatability of diluted chicken manure (with an influent feed ratio of 1 kg of fresh chicken manure to 6 L of tap water) was investigated in a lab-scale anaerobic sludge bed (ASB) reactor inoculated with granular seed sludge. The ASB reactor was operated at ambient temperature (17-25°C) in order to avoid the need of external heating up to higher operating temperatures (e.g., up to 35°C for mesophilic digestion). Since heat requirement for raising the temperature of incoming feed for digestion is eliminated, energy recovery from anaerobic treatment of chicken manure could be realized with less operating costs. Average biogas production rates were calculated ca. 210 and 242 L per kg of organic matter removed from the ASB reactor at average hydraulic retention times (HRTs) of 13 and 8.6 days, respectively. Moreover, average chemical oxygen demand (COD) removal of ca. 89% was observed with suspended solids removal more than 97% from the effluent of the ASB reactor. Influent ammonia, on the other hand, did not indicate any free ammonia inhibition due to dilution of the raw manure while pH and alkalinity results showed stability during the study. Microbial quantification results indicated that as the number of bacterial community decreased, the amount of Archaea increased through the effective digestion volume of the ASB reactor. Moreover, the number of methanogens displayed an uptrend like archaeal community and a strong correlation (-0.645) was found between methanogenic community and volatile fatty acid (VFA) concentration especially acetate.

Seasonal variation of diclofenac concentration and its relation with wastewater characteristics at two municipal wastewater treatment plants in Turkey.

The pharmaceutically active compound diclofenac has been monitored during one year at separate treatment units of two municipal wastewater treatment plants (WWTPs) to evaluate its seasonal variation and the removal efficiency. Conventional wastewater characterization was also performed to assess the possible relationship between conventional parameters and diclofenac. Diclofenac concentrations in the influent and effluent of both WWTPs were detected in the range of 295-1376 and 119-1012ng/L, respectively. Results indicated that the higher diclofenac removal efficiency was observed in summer season in both WWTPs. Although a consistency in diclofenac removal was observed in WWTP_1, significant fluctuation was observed at WWTP_2 based on seasonal evaluation. The main removal mechanism of diclofenac in the WWTPs was most often biological (55%), followed by UV disinfection (27%). When diclofenac removal was evaluated in terms of the treatment units in WWTPs, a significant increase was achieved at the treatment plant including UV disinfection unit. Based on the statistical analysis, higher correlation was observed between diclofenac and suspended solids concentrations among conventional parameters in the influent whereas the removal of diclofenac was highly correlated with nitrogen removal efficiency.

Biomethane production as an alternative bioenergy source from codigesters treating municipal sludge and organic fraction of municipal solid wastes.

Energy recovery potential of a mesophilic co-digester treating OFMSW and primary sludge at an integrated biomethanization plant was investigated based on feasibility study results. Since landfilling is still the main solid waste disposal method in Turkey, land scarcity will become one of the most important obstacles. Restrictions for biodegradable waste disposal to sanitary landfills in EU Landfill Directive and uncontrolled long-term contamination with gas emissions and leachate necessitate alternative management strategies due to rapid increase in MSW production. Moreover, since energy contribution from renewable resources will be required more in the future with increasing oil prices and dwindling supplies of conventional energy sources, the significance of biogas as a renewable fuel has been increased in the last decade. Results indicated that almost 93% of annual total cost can be recovered if 100% renewable energy subsidy is implemented. Besides, considering the potential revenue when replacing transport fuels, about 26 heavy good vehicles or 549 cars may be powered per year by the biogas produced from the proposed biomethanization plant (PE = 100,000; X(PS) = 61 g TS/PE·day; X(SS-OFMSW) = 50 g TS/PE·day).

High-rate anaerobic treatment of domestic wastewater at ambient operating temperatures: A review on benefits and drawbacks.

This paper reviews the current knowledge on high-rate anaerobic sewage treatment at ambient operating temperatures while presenting the benefits and drawbacks. Since domestic sewage is reported as the main point-source pollutant on a global scale, its treatment deserves ample research. In most of the cities and towns of some developing countries, wastewater produced in households is still discharged into the nearest water body without subjected any treatment. Therefore, simple, affordable, and effective sewage treatment systems are required. Anaerobic digestion of wastewater is reported as a sustainable alternative as recovery of energy is provided while nutrients are preserved for reuse. Anaerobic sewage treatment is certainly not limited to regions of hot climates but it also offers treatment potential in sub-tropical and even in moderate climatic regions due to their favorable temperature conditions. Since many sewage-like dilute wastewaters are discharged at low ambient temperatures especially under moderate climate conditions (15 to 20 degrees C), heating the wastewater to maintain mesophilic conditions (35 degrees C) for anaerobic treatment necessitates high energy and certainly high operating costs. Thus, the development of anaerobic treatment systems operated at ambient temperatures without doubt will have a great ecological and economic impact. High-rate anaerobic treatment systems, especially upflow anaerobic sludge blanket (UASB) reactors, have been occupying a noticeable position for sewage treatment in several tropical countries where artificial heating can be eliminated. However, in spite of their undeniable advantages, there are certain drawbacks of anaerobic sewage treatment at low operating temperatures which should be clarified. Among them, the main concern for anaerobic treatment application is its producing effluents that barely comply with the standarts for reuse in agriculture or discharge to the environment. Therefore, the effluents from anaerobic reactors usually necessitate a post-treatment step as a mean to protect the receiving water bodies. However, anaerobic sewage treatment when combined with a proper post-treatment, provides a sustainable, appropriate, and affordable method especially for developing countries.

Co-digestion of the organic fraction of municipal solid waste with primary sludge at a municipal wastewater treatment plant in Turkey.

Co-digestion of the organic fraction of municipal solid waste (OFMSW) and sewage sludge may be an attractive alternative for sustainable management of two separate waste streams produced in large amounts in all countries. This study evaluates calculation-based results of an anaerobic co-digestion process for primary sludge (PS) together with the OFMSW. The calculations were carried out for the anaerobic digester of Kayseri municipal wastewater treatment plant (in Turkey) presently digesting only PS. Two alternatives were proposed using different solid waste contents in co-digesters. For achieving the optimal solids content, some treated wastewater should be recycled to the inlet of the digesters. The municipal solid waste collection method characterized as mechanically sorted (MS-OFMSW; Option 1) is evaluated as well as a source sorted (SS-OFMSW) alternative (Option 2). Utilizing the energy produced by the existing sludge digester, only 30% of the internal energy demand at the wastewater treatment plant can be covered. The aim of this study is to evaluate how energy production would be increased by co-digestion of OFMSW and PS. The best operational condition considering organic loading rate, hydraulic retention time and energy generation could be attained at 10% digester solids content for both options. According to Option 1, almost 77% of the energy demand could be covered by co-digestion of MS-OFMSW and PS. Results indicated that almost 100% energy coverage can be obtained when co-digestion (Option 2) was performed according to SS-OFMSW and PS.

Identification of Archaeal population in the granular sludge of an UASB reactor treating sewage at low temperatures.

Effect of low temperature on up-flow anaerobic sludge bed (UASB) reactor performance treating raw sewage was investigated in terms of the variations in methanogenic diversity using the 16S rRNA based Fluorescence In-Situ Hybridization (FISH) technique. The diversity of microorganisms present in the anaerobic granular sludge and the structure of the granules operated at 13 degrees C have been investigated using FISH combined with CSLM (Confocal Scanning Laser Microscopy). According to FISH results, archaeal cells representing methanogens were found intensively dominant in the bottom sampling port of the UASB reactor and acetoclastic Methanosaeta was the abundant methanogen. Other methanogens such as Methanosarcina and Methanobacterium like species were also observed. The abundance of originally mesophilic Methanosaeta-related Archaea under low temperature at all sampling days revealed the microbial adaptation to psychrophilic conditions. This might be attributed to the enzymatic alterations in Methanosaeta cells originating from seed sludge, which were exposed to sub-mesophilic temperatures at start-up and then to psychrophilic conditions during gradual decreases of temperature. According to CSLM observation, even though the sludge retained in the reactor kept its granular form as a whole, the majority of the granules had a tendency to be partly broken and they lost their rigidity when raw sewage was fed following synthetic sewage. Besides, Methanosaeta related species prevailing in seed sludge have noticeably lost their long filamentous forms and deteriorated during raw sewage feeding. Members of the order Methanobacteriales constituted the major hydrogenothrophic methanogens present in the psychrophilic UASB reactor, whereas the other hydrogenothrophic methanogens--members of the order Methanococcales and Methanogenium relatives--were absent.

Advanced oxidation treatment of physico-chemically pre-treated olive mill industry effluent.

In this study, the applicability of physico-chemical methods was investigated for the pre-treatment of the olive mill effluents prior to the discharge into the common sewerage ending with a municipal wastewater treatment plant. The samples were taken from an olive oil industry operated as three-phase process located in Turkey. Various pre-treatment methods including acid craking, polyelectrolyte and lime additions were applied. Advanced oxidation study using Fenton's process was also investigated following pre-treatment by acid cracking and cationic polyelectrolyte. Acid cracking alone gave satisfactory treatment efficiencies and polyelectrolite additions to the acid-cracked samples enhanced treatment efficiency. Since a complete treatment plant is available at the end of the sewer system, results indicated that the effluents of the investigated industry could be discharged into the municipal sewerage in the case of total chemical oxygen demand (COD(tot)), suspended solid (SS) and volatile suspended solid (VSS) concentrations according to the Turkish Water Pollution Control Regulation after pre-treatment with 5 ppm anionic polyelectrolyte following acid cracking. The minimum COD(tot), SS and VSS removals were observed when raw wastewater was pre-treated with lime and the discharge standards to the municipal sewer system could not be met. Advanced oxidation with Fenton's process was applied after acid cracking and cationic polyelectrolyte treatment in order to investigate further reduction in chemical oxygen demand (COD) concentration for minimizing the influence of this industrial discharge on the existing municipal wastewater treatment plant. Results indicated that COD(tot) removal increased up to 89% from 74% after Fenton's oxidation for the acid cracked samples in which cationic polyelectrolite (10 ppm) was added.

Behavior of the anaerobic CSTR in the presence of scum during primary sludge digestion and the role of pH.

Anaerobic digestion of the primary sludge with or without scum addition and the role of pH were evaluated in four completely stirred tank reactors (CSTR) operated as batch systems at 35 degrees C (mesophilic). For investigating the scum influence, two CSTRs were only fed with the primary sludge (PS) whereas the other CSTRs were composed of the primary sludge with 15% scum (PS+Scum). The pH in two reactors was fixed at 6.5, whereas the pH in the other two reactors was left to be operated at their original values for evaluating the retardation in biodegradation rates at low pH values. Since scum is generally produced at most primary settling tanks and given into the anaerobic digesters, the behavior of the CSTR was examined with or without scum addition. The results indicated that scum addition favoured low pH levels and led to retardation in methanogenesis. Besides, pH control enhanced the biodegradation rates and led to methanogenesis to perform at shorter digestion times in the reactors. The destructions of TSS and VSS were better when the pH was controlled. When only primary sludge was used as the substrate, the reactors with or without pH control removed VSS with a corresponding production of VFAs and soluble COD. However, their productions ceased earlier and the complete VFAs consumption occurred 4 days earlier in the reactors with pH control. In the reactors consisting of PS+Scum, soluble COD productions continued during 4 days of digestion. However, soluble COD remained constant and almost no VFAs consumption occurred during the whole operation period without pH control whereas VFAs were consumed completely after around 11 days in the reactor with pH control. Overall, scum addition caused methanogenesis to perform at longer operation periods when the pH was controlled and kept above 6.5. When the pH was not controlled, scum favoured acidic conditions and did not allow methanogenesis to start due to the fact that methanogens could not perform well at low pH levels.

Anaerobic digestion of municipal sludges with high silt content using granular seed.

The performance of anaerobic digestion of municipal sludge having high inorganic solid/silt in Tuzla Wastewater Treatment Plant (TWWTP) in Istanbul was evaluated using granular seed. High silt/solid content is the main problem related to wastewater collection system in TWWTP. Due to high TSS concentration of the influent, inorganic solid ratio reaches to 60-70% in the primary sludge that makes sludge digestion very difficult. The aim of this study was to evaluate the detrimental effects of inorganic silt/clay on anaerobic sludge solubilization of the primary sludge (PS), of the biological sludge (BS), and of the mixed sludge (50%PS + 50%BS). Anaerobic solubilization was carried out in continuously stirred anaerobic reactors at mesophilic temperature (35 degrees C). Results indicated significant total biogas productions in all reactors during digestion period. The biogas production of the primary sludge was higher than the biogas productions of the mixed sludge and the biological sludge. The methane contents of the primary, biological. and mixed sludges were found as around 72, 78, and 75%, respectively. When all types of sludges were used as substrates, the reactors removed VSS with a corresponding production of Soluble COD (SCOD). The greatest degree of hydrolysis/acidogenesis was observed in all types of sludges in about 10 days of operation and became almost stable which indicated that the reactors were still in the hydrolysis/acidogenesis phase. VFAs measurements were well matched with SCOD results. In all reactors, observation of the conversion into methanogenic phase in about 1.5 month was not possible which might be attributed to high inorganic silt/clay and salinity content of TWWTP. High inorganic silt/clay and salinity might have decreased the biodegradability of all sludges and methanogenesis could not operate in early periods of digestion. Higher SCOD decreases might have been possible if longer treatment time and more optimal conditions for anaerobic solubilization were applied. The pH did not fall below the unfavorable range in all reactors during the study.

The role of pH in mesophilic anaerobic sludge solubilization.

The effect of pH on anaerobic solubilization of synthetic sludge (dog food) and domestic primary sludge was investigated and compared. Anaerobic solubilization was carried out in Continuously Stirred Anaerobic Reactors at mesophilic temperature (35 degrees C) and pH was fixed at 6.5 (pH-controlled). The aim of pH control in the reactors consisting of synthetic and primary sludge, was the evaluation of retardation in hydrolysis/acidogenesis at low pH values. Since synthetic and primary sludge have different biodegradation characteristics, the results were compared. In both sludges, acetic acid was the main Volatile Fatty Acids (VFAs) produced. Volatile Suspended Solid (VSS) reduction was found as 67% in about 20 days in the anaerobic digestion of synthetic sludge. whereas for the same interval VSS reduction could only be achieved by 32% in primary sludge at 35 degrees C in the pH-controlled reactors. When both types of sludges were used as substrates, the reactors removed VSS with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). However, in the pH-controlled reactors production of VFAs and SCOD was ceased after 5 days in primary sludge whereas VFAs and SCOD production continued after 5 days in synthetic sludge which indicated that hydrolysis and fermentation in the anaerobic solubilization reactors were not complete and continued longer. On the other hand, in the pH-controlled reactor of primary sludge, methanogenic phase could operate after 5 days of operation as hydrolysis/acidogenesis stopped.