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.

Modification of reinforced hollow fiber membranes with WO3 nanosheets for treatment of textile wastewater by membrane bioreactor.

In this study, performance of braid reinforced hollow fiber membrane containing polyvinylidene fluoride (PVDF) embedded with tungsten trioxide (WO3) nanosheets in a membrane bioreactor (MBR) was examined for textile wastewater treatment. The WO3 nanosheets was synthesized and blended at different concentrations (0.1-0.02 wt%) in casting solutions of the membranes. The WO3 nanosheets characterized using various tests such as XRD, FTIR, SEM, EDS, dot-mapping, and TEM. Furthermore, the effects of the increased WO3 nanosheets into the PVDF matrix on the membrane morphology, hydrophilicity, permeability, antifouling, and COD and color removal efficiency was investigated. The addition of 0.1 wt% of the nanosheets reduces the water contact angle from 69.3° to 62.5° while increasing overall porosity from 37.5 to 43.2%. COD and color removal for PVDF/0.10 wt% WO3 membrane was between 86-89% and 72-76%, respectively. While the TMP of modified WO3 membranes did not significantly increase due to antimicrobial properties of the WO3 nanosheets, the TMP of the pure PVDF membrane increase, indicating considerable cake layer fouling. The results of this study showed that modification of PVDF braid reinforced hollow fiber membrane using WO3 nanosheets is promising membrane for MBR systems.

Cellulose acetate in fabrication of polymeric membranes: A review.

Developing biodegradable polymers to fabricate filtration membranes is one of the main challenges of membrane science and technology. Cellulose acetate (CA) membranes, due to their excellent film-forming property, high chemical and mechanical stability, high hydrophilicity, eco-friendly, and suitable cost, are extensively used in water and wastewater treatment, gas separation, and energy generation purposes. The CA is one of the first materials used to fabricate filtration membranes. However, in the last decade, the possibility of modification of CA to improve permeability and stability has attracted the researcher's attention again. This review is focused on the properties of cellulose derivatives and especially CA membranes in the fabrication of polymeric separation membranes in various applications such as filtration, gas separation, adsorption, and ion exchange membranes. Firstly, a brief introduction of CA properties and used molecular weights in the fabrication of membranes will be presented. After that, different configurations of CA membranes will be outlined, and the performance of CA membranes in several applications and configurations as the main polymer and as an additive in the fabrication of other polymer-based membranes will be discussed.

Impact of salinity on the population dynamics of microorganisms in a membrane bioreactor treating produced water.

Biomass characteristics may change subject to a salinity increase when treating high strength wastewater. In this study, the impact of salinity in a membrane bioreactor (MBR) was investigated for the treatment of produced water (PW). MBR was operated as a pre-treatment prior to nanofiltration (NF) and reverse osmosis (RO). Mixed PW, that was originated from different oil, gas, and oil-gas wells, were subjected to pre-treatment for 146 days including three different operational phases: Low-salinity (~10 mS/cm), gradual increased salinity (10-40 mS/cm) and high salinity (~40 mS/cm). The results of this study showed that microorganisms could adapt using real wastewater and treat PW up to a certain level of the salinity. At high salinity levels of PW, the floc structure started to be disrupted and membrane fouling was accelerated. PCR-DGGE analysis confirmed the changes in microbial communities' composition in relation with high salinity. The results of the final treatment experiments presented that NF and RO treatment produced high-quality effluents that could be suitable for reuse.

Treatment of produced water originated from oil and gas production wells: a pilot study and cost analysis.

Produced water originated from oil and gas production wells was treated by a pilot-scale system including pre-treatment (chemical precipitation), pre-filtration, and post-filtration units. Pre-filtration unit consisted of sand filter, granulated activated carbon (GAC) filter, and ultrafiltration (UF) membrane. Post-filtration unit included reverse osmosis (RO) membrane unit. In this study, two different RO membranes including sea water (SW) and brackish water (BW) membranes were comparatively evaluated in terms of treatment and filtration performance. Besides, a cost analysis was conducted for a real scale RO membrane unit by using the data obtained from the pilot plant study. Average fluxes of 12.7 and 9.4 L/m2 h were obtained by SW and BW membrane units, respectively. Higher COD and conductivity removal efficiencies were obtained by SW membrane in comparison to BW membrane. Total cost of 0.88 €/m3 was estimated for a RO plant treating produced water with a flowrate capacity of 300 m3/d.

An Autopsy of Nanofiltration Membrane Used for Landfill Leachate Treatment.

Komurcuoda leachate treatment plant, Istanbul, which consists of membrane bioreactor (MBR) and nanofiltration (NF) system, faced rapid flux decline in membranes after 3-year successful operation. To compensate rapid flux decline in membranes, the fouled membranes were renewed but replacement of the membranes did not solve the problem. To find the reasons and make a comprehensive analysis, membrane autopsy was performed. Visual and physical inspection of the modules and some instrumental analysis were conducted for membrane autopsy. Membranes were found severely fouled with organic and inorganic foulants. Main foulant was iron which was deposited on surface. The main reason was found to be the changing of aerator type of MBR. When surface aerators were exchanged with bottom diffusers which led to increasing of dissolved oxygen (DO) level of the basin, iron particles were oxidized and they converted into particulate insoluble form. It was thought that probably this insoluble form of the iron particles was the main cause of decreased membrane performance. After the diagnosis, a new pretreatment alternative including a new iron antiscalant was suggested and system performance has been recovered.