Landfill leachate treatment with a full-scale membrane bioreactor: impact of leachate characteristics on filamentous bacteria.

Bulking and foaming are extreme filamentous bacterial growths that present serious challenges for the biological leachate treatment process. The current study evaluates the performance of long-term full-scale membrane bioreactor (MBR) treating landfill leachate, specifically focusing on filamentous bacteria overgrowth in the bioreactors. The influence of the variation in leachate structure and operational conditions on floc morphology and filamentous bacteria overgrowth were analyzed for 11 months of operation of the full-scale MBR system. The average chemical oxygen demand (COD) and NH4-N removal efficiencies of the system were 87.8 ± 4% and 99.5 ± 0.7%. However, incomplete denitrification was observed when the F/M ratio was low. The high C/N ratio was observed to enhance the frequency of small flocs. Furthermore, a poor to medium diversity of the microbial community was observed. Haliscomenobacter hydrossis, Microthrix parvicella, and Type 021N were found as the most numerous filamentous organisms. Paramecium spp., Euplotes spp., and Aspidisca spp. were found in small quantities. The limited concentration of PO4-P in the leachate compared to high COD and NH4-N concentrations most probably caused phosphate deprivation and increased abundance of identified filamentous microorganisms. This work is the first study in Türkiye that investigates the bulking and foaming problem in full-scale MBR that treats landfill leachate. Hence, it may provide some pioneering perspectives into landfill leachate remediation by monitoring the hybrid biological system.

Enhanced removal of antibiotics using Eichhornia crassipes root biomass in an aerobic hollow-fiber membrane bioreactor.

The impact of water hyacinth (Eichhornia crassipes) root biomass (WHRB) on pharmaceutical wastewater treatment with an aerobic hollow-fiber membrane bioreactor (HF-MBR) was investigated. The performance of the bioreactor was assessed in terms of COD (Chemical Oxygen Demand) and antibiotic removal and membrane biofouling rate. For deeper insight, microbial communities in sludge and biofilm layers were analyzed through Illumina sequencing. The addition of WHRB into the HF-MBR increased the COD (by 6%), as well as antibiotics and transformation products removal efficiency. Removal efficiencies of 97%, 98% and 84% were obtained for removal of erythromycin, sulfamethoxazole, and tetracycline. Furthermore, WHRB modified the biodegradation network, increased the relative abundances of Chloroflexi, Proteobacteria and Nitrospirae and decreased Firmicutes, compared with the control with antibiotics. The addition of WHRB also enriched Actinobacteria and Bacteroidetes while decreasing the phylla Chloroflexi and Saccharibacteria in the biofilm.

Eichhornia crassipes root biomass to reduce antibiotic resistance dissemination and enhance biogas production of anaerobic membrane bioreactor.

ABSTRACTTo address the inadequate removal of antibiotic resistance genes in wastewater treatment plants, this study investigated the impact of bioaugmentation with dried Eichhornia crassipes roots on removal of antibiotics sulfamethoxazole, tetracycline and erythromycin from pharmaceutical wastewater while optimizing potential for reclaiming value through biogas production, utilizing an anaerobic membrane bioreactor (AnMBR). Three sets of AnMBRs were set up for the experiment, C1 (inoculum), C2 (inoculum + antibiotics) and EC (inoculum + antibiotics + E. crassipes). The results showed that E. crassipes mitigated some of the toxic effects of antibiotics on the microbial community and prevented negative impact on the archaeal community, and significantly increased average biogas production (by 37% compared to control without antibiotics and 42% compared to control with antibiotics) as well as antibiotics removal. Furthermore, bioaugmented reactor showed significant reduction of erythromycin (97%) and tetracycline (83%) concentrations in effluent. Utilization of E. crassipes root offers a simple yet powerful tool for preventing the emergence of antimicrobial resistance and dissemination of such pollutants into the environment.

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.

Bioaugmentation with immobilized endophytic Penicillium restrictum to improve quorum quenching activity for biofouling control in an aerobic hollow-fiber membrane bioreactor treating antibiotic-containing wastewater.

The effects of bioaugmentation with immobilized Penicillium restrictum on the removal efficiency of sulfamethoxazole (SMX), erythromycin (ERY) and tetracycline (TC) antibiotics as well as membrane biofouling was studied using hollow-fiber membrane bioreactor (HF-MBR). Bioaugmentation with P. restrictum led to a significant change in the antibiotic removal efficiency and relative abundance of aerobic microbial community, most probably as a result of its quorum quenching activity. Furthermore, in addition to its role in the increase of SMX and ERY removal efficiencies and the decrease of their sorption on solid phase, bioaugmentation significantly reduced the transmembrane pressure which in turn reduced membrane clogging. The most abundant phyla in sludge and biofilm samples in the presence of P. restrictum were observed to be Proteobacteria, Bacteroidetes and Firmicutes. Differences in bacterial compositions and their specificity in biodegradation of antibiotics in different reactors showed that bacteria were specifically selected under the pressure of antibiotics and growing fungus.

Long-term MBR performance of polymeric membrane modified with Bismuth-BAL chelate (BisBAL).

An ultrafiltration membrane prepared by polyethersulfone (PES) was modified with Bismuth-BAL chelate (BisBAL) and was used in submerged membrane bioreactor system. Moreover, a control membrane reactor was also tasked to evaluate the effect of BisBAL on the membrane performance. The flux profile, transmembrane pressure, the effect of chemical treatment, cake layer formation, anti-fouling properties against extracellular polymeric substances (EPS) and soluble microbial products (SMP) were studied. The UF modified membrane demonstrated a sustained permeability, low cleaning frequency, and longer filtration time. In terms of anti-EPS and SMP accumulation, the modified membrane showed a lower membrane resistance. It can be illustrated from scanning electron microscopy and confocal laser scanning microscope images that the modified membrane had presented better properties than bare PES membrane, as it was looser and thinner. Thus, the UF membrane proved to be more efficient in terms of permeability and lifetime.

Effects of high-concentration influent suspended solids on aerobic granulation in pilot-scale sequencing batch reactors treating real domestic wastewater.

The aim of this study was to investigate the effect of high-influent-concentration suspended solids (SS) on the cultivation, structure and long-term stability of aerobic granular sludge (AGS). Cultivation and long-term stability of AGS were monitored in two pilot-scale sequencing batch reactors fed with raw (R1) and settled (R2) domestic wastewater, representing high and medium SS content, respectively. The real domestic wastewater had high chemical oxygen demand (COD) content (1100 ±â€¯270 mg COD L-1). Aerobic granular sludge was cultivated in 44 days (R1) and 25 days (R2) under the conditions of high settling velocity (18 m h-1) and high organic loading rate (OLR) (2.1-2.4 kg COD m3 day). The AGS in both reactors had similar structural properties during long-term operation and remained structurally and functionally stable during the last five months of operation. Comparative evaluation of the results indicated that the high influent SS content of the real domestic wastewater had a positive influence on maintaining significantly lower SVI30 and relatively lower effluent SS concentration. Moreover, a higher influent SS content resulted in smaller mature granules during the stable period. Microbial community analyses helped to understand the aerobic granular sludge structure and showed that the sludge retention time and OLR affected the granular sludge population. The high influent SS increased biomass detachment from the granular sludge surface and caused wash-out of some bacteria colonizing the exterior of the granular sludge.

Effect of simultaneous nitrification and denitrification on nitrogen removal performance and filamentous microorganism diversity of a full-scale MBR plant.

The nutrient removal performance of a membrane bioreactor (MBR) plant treating the wastewater of 10,000 PE was investigated with dynamic simulations. The average process performance with respect to chemical oxygen demand and total nitrogen were reported to be 97 and 81%, respectively. The modeling study showed that low dissolved oxygen (DO) levels (0.2-0.3 mgO2/L) due to limited aeration capacity within aeration tank that provided additional total nitrogen removal of 15-20 mgN/L. Simultaneous nitrification and denitrification process was found to be the reason of performance increase. However, low DO levels <0.3 mgO2/L in the aeration tank triggered the proliferation of filamentous microorganisms within one month as a side effect. In this respect, the morphotypes of Type 0092 and Nocardia (Gordonia) amarae were found to be excessively abundant in the MBR system. Overflow of foam layer covering the tanks was frequently reported during bulking period. A hypochloride dosing of 4.5 gCL/kgMLSS/day was applied to get over filamentous bulking problem as a short term action.

Biodegradability and denitrification potential of settleable chemical oxygen demand in domestic wastewater.

The effect of settling on mass balance and biodegradation characteristics of domestic wastewater and on denitrification potential was studied primarily using model calibration and evaluation of oxygen uptake rate profiles. Raw domestic wastewater was settled for a period of 30 minutes and a period of 2 hours to assess the effect of primary settling on wastewater characterization and composition. Mass balances in the system were made to evaluate the effect of primary settling on major parameters. Primary settling of the selected raw wastewater for 2 hours resulted in the removal of 32% chemical oxygen demand (COD), 9% total Kjeldahl nitrogen, 9% total phosphorus, and 47% total suspended solids. Respirometric analysis identified COD removed by settling as a new COD fraction, namely settleable slowly biodegradable COD (X(ss)), characterized by a hydrolysis rate of 1.0 day(-1) and a hydrolysis half-saturation coefficient of 0.08. A model simulation to test the fate and availability of suspended (X(s)) and settleable (X(ss)) COD fractions as carbon sources for denitrification showed that both particulate COD components were effectively removed aerobically at sludge ages higher than 1.5 to 2.0 days. Under anoxic conditions, the biodegradation of both COD fractions was reduced, especially below an anoxic sludge retention time of 3.0 days. Consequently, modeling results revealed that the settleable COD removed by primary settling could represent up to approximately 40% of the total denitrification potential of the system, depending on the specific configuration selected for the nitrogen removal process. This way, the results showed the significant effect of primary settling on denitrification, indicating that the settleable COD fraction could contribute an additional carbon source in systems where the denitrification potential associated with the influent becomes rate-limiting for the denitrification efficiency.

Effect of hypochloride on microbial ecology of bulking and foaming activated sludge treatment for tannery wastewater.

This study investigates the effect of hypochloride application for controlling bulking and foaming on the microbial ecology of an activated sludge system treating tannery wastewater. Detailed characterization of the wastewater treatment influent and effluent is also reported for the study period. During the study, bulking and foaming are first monitored with a sudden burst in the sludge volume index over 250 mL g(-1), creating a significant deterioration of the effluent quality. The corresponding upset in the microbial ecology is the combined excessive proliferation of M. parvicella, N. limicola II and Gordona (Nocardia) spp., but mainly triggered by Gordona contamination of the floc structure and the rapid outward growth of this filamentous microorganism extending to adjacent flocs. Chlorine application at an average rate of 3 g Cl(-1)(kg MLSS.day)(-1) for 12 days provide an effective solution for bulking and foaming, restoring the effluent quality. It destroys filamentous texture between the flocs, leaving only a lot of loose and chopped filament fragments and, totally removes the Gordona spp. from solution which retrieves back into the flocs. Therefore, chlorine remediation of bulking and foaming, although temporarily effective, is only superficial as the Gordona seeding inside the floc remains intact and potentially available for excessive growth in the next favorable conditions.

Microbial ecology of bulking and foaming activated sludge treating tannery wastewater.

This study involves a comprehensive survey of the microbial ecology of the activated sludge process treating tannery wastewater, emphasizing evaluation during periods of bulking and foaming. The survey also includes a detailed characterization of process influent and effluent. Observations always associate bulking with significant increase in protozoa species and rotifers, but decrease or disappearance of nematodes. Activated sludge sustained under normal conditions with a sludge volume index lower than 80 ml g(-1), exhibits all the properties of a compact and healthy zoogleal floc structure. Three types of filamentous bacteria prevail in the microscopic examinations. Two of the filamentous bacteria, Microthrix parvicella and Nostocoida limicola II, always appear as components of the floc structure under normal conditions and abundant or even excessive levels. The study identifies Gordona spp. as the main microorganism responsible for bulking and foaming, which starts by a Gordona contamination process inside the floc, later branching out and extending through adjacent flocs. When completed, this process increases sludge volume index values to over 200 ml g(-1). Microscopic examinations indicate significant morphological differences between filamentous microorganisms observed in this study and reported in the literature mostly for domestic sewage treatment.

Bacteriological indicators of anthropogenic impact prior to and during the recovery of water quality in an extremely polluted estuary, Golden Horn, Turkey.

Five years of monthly data of indicator bacteria from 1998 to 2002 were evaluated to find out the changes in water quality during the rehabilitation of the Golden Horn, an estuary severely polluted from industrial and domestic discharges since the 1950s. Surface fecal coliform was above 10(6) CFU/100 ml at the inner part in 1998. Following the achievement of healthy water circulation and control of most surface discharges, fecal coliform and fecal streptococci counts decreased below 10(3) CFU/100 ml in the summer of 2002. However, the decrease was interrupted by sudden shifts in rainy periods. Runoff, enhanced by domestic inputs during rainfall, has become the main factor influencing water quality in the estuary today. Increasing values of fecal coliform were observed during periods of low salinity, pH, dissolved oxygen and high ortho-phosphate, whilst decreasing values were detected during high salinity, pH and dissolved oxygen and low ortho-phosphate periods. Striking changes were observed within five years, promising that even an anoxic water body can turn into a recreational area with appropriate treatment.

Conventional morphological and functional evaluation of the microbial populations in a sequencing batch reactor performing EBPR.

To help confirm and interpret the Enhanced Biological Phosphorus Removal (EBPR) performance of the microbial populations in a laboratory-scale activated sludge (AS) system, conventional microscopic examinations were carried out. A lab-scale sequencing batch reactor (SBR), named ARC, was fed with acetate, as the sole carbon source, and operated for EBPR. Daily monitoring and cyclic behavior evaluation studies indicated that the system always worked for EBPR in the long run, with efficiencies depending on the influent characteristics and operational stability. Poly-P and PHB-staining experiments revealed that the enriched biomass of the reactor was quite diverse in terms of morphology, hosting populations of traditional rod-shaped PAOs, tetrad/sarcina-like cells (referred here as TFOs, rather than GAOs), diplococci-shaped cells, and staphylococci-like clustered populations, in addition to few filaments. Although the microscopic observations were qualitative, rather than quantitative, they seemed likely to correlate well to the biochemical performance of the reactor.

Enhanced biological phosphate removal by granular sludge in a sequencing batch reactor.

A laboratory-scale sequencing batch reactor was started-up with flocculated biomass and operated primarily for enhanced biological phosphate removal. Ten weeks after the start-up, gradual formation of granular sludge was observed. The compact biomass structure allowed halving the settling time, the initial reactor volume, and doubling the influent COD concentration. Continued operation confirmed the possibility of maintaining a stable granular biomass with a sludge volume index less than 40 ml g-1, while securing a removal efficiency of 95% for carbon, 99.6% for phosphate, and 71% for nitrogen. Microscopic observations revealed a morphological diversity.