Separation, Characterization and Fouling Potential of Sludge Waters from Different Biological Wastewater Treatment Processes

The major limitation, which hinders the wider application of membrane technology and increases the operating costs of membranes involved in wastewater treatment plants, is membrane fouling induced by organic matter. Extracellular polymeric products (EPS) and soluble microbial products (SMP) are the two most mentioned major foulants in publications, for which the debate on precise definitions seems to be endless. Therefore, a concept of sludge water, which conceptually covers both EPS and SMP, has been developed in this research. A standard procedure of sludge water separation, which is centrifugation at 4000g for 15 min followed by 1.2μm glass fiber filter filtration, was established based on separation experiments with membrane tank sludge from the KAUST MBR wastewater treatment plant. Afterwards, sludge waters from the KAUST MBR WWTP anoxic tank, aerobic tank and membrane tank as well as sludge waters from the Jeddah WWTP anoxic tank, aerobic tank and secondary effluent were produced through the previously developed standard procedure. The obtained sludge water samples were thereafter characterized with TOC/COD, LC-­-OCD and F-­-EEM, which showed that KAUST anoxic/ aerobic /membrane tank sludge waters had similar characteristics for all investigated parameters, yet the influent naturally had a higher DOC and biopolymer concentration. Moreover, lower TOC/COD, negligible biopolymers and low levels of humics were found in KAUST effluent. Compared with the KAUST MBR WWTP, the Jeddah WWTP’s sludge waters generally had higher DOC and biopolymer concentrations. To investigate sludge water fouling potential, the KAUST membrane tank sludge water as well as the Jeddah secondary effluent were filtrated through a membrane array consisting of an ultrafiltration (UF) Millipore RC10kDa at the first step followed by a nanofiltration (NF) KOCH Acid/Base stable NF200 at the second step. It was found that cake layer and standard blocking occurred simultaneously during both of these filtration processes. For the KAUST MBR membrane tank sludge water and the Jeddah WWTP effluent, the fouling potential of humic/building blocks was much higher than that of biopolymers. Compared with the KAUST MBR membrane tank sludge water, the Jeddah WWTP effluent had comparable biopolymer fouling potential and higher humic/building blocks fouling potential

Double Trouble of Air Pollution by Anthropogenic Dust

With urbanization worldwide in recent decades, anthropogenic dust (AD) emissions due to heavy urban construction and off-road vehicle use have been increasing. Its perturbations on urban air pollution at the global scale are still unclear. Based on observations, we found that a high urban AD optical depth is often accompanied by severe non-dust aerosol optical depth in the planetary boundary layer (PBL), both magnitudes even comparable. To investigate the causes, an AD emission inventory constrained by satellite retrievals is implemented in a global climate model. The results show that AD-induced surface radiative cooling of up to -15.9 +/- 4.0 W m(-2) regionally leads to reduced PBL height, which deteriorates non-dust pollution, especially over India and northern China, in addition to the tremendous direct AD contribution to pollutants. The estimated global total premature mortality due to AD is 0.8 million deaths per year and is more severe in populous regions.Peer reviewe

Analytical Methods for Pesticides and Herbicides

A review of the literatures published in 2017 on topics relating to analytical methods for pesticides and herbicides is presented in this paper. Based on different techniques, this review is divided into seven parts, i. e., extraction methods, chromatographic or mass spectrometric techniques, electrochemical techniques, spectrophotometric techniques, chemiluminescence and fluorescence methods, biochemical assays and immunoassays, and miscellaneous techniques

Physico-Chemical Processes

This review covers research articles published in 2017 on topics relating to physico-chemical processes for water and wastewater treatment. The paper divides into nine sections, i. e., membrane technology, ion exchange, capacitive deionization, granular filtration, coagulation/flocculation, sedimentation, flotation, oxidation and adsorption. The membrane technology part includes six parts, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), and membrane distillation (MD)

The role of ozone pretreatment on optimization of membrane bioreactor for treatment of oil sands process-affected water

Previously, anoxic-aerobic membrane bioreactor (MBR) coupled with mild ozonation pretreatment has been applied to remove toxic naphthenic acids (NAs) in oil sands process-affected water (OSPW). To further improve MBR performance, the optimal operation conditions including hydraulic retention time (HRT) and initial ammonia nitrogen (NH4+-N) need to be explored. In this study, the role of ozone pretreatment on MBR optimization was investigated. Compared with MBR treating raw OSPW, MBR treating ozonated OSPW had the same optimal operation conditions (HRT of 12 h and NH4+-N concentration of 25 mg/L). Nevertheless, MBR performance benefited from HRT adjustment more after ozone pretreatment. HRT adjustment resulted in NA removal in the range of 33–50% for the treatment of ozonated OSPW whereas NA removal for raw OSPW only fluctuated between 27% and 38%. Compared with the removal of classical NAs, the degradation of oxidized NAs was more sensitive to the adjustment of operation conditions. Adjusting HRT increased the removal of oxidized NAs in ozonated OSPW substantially (from 6% to 35%). It was also noticed that microbial communities in MBR treating ozonated OSPW were more responsive to the adjustment of operation conditions as indicated by the noticeable increase of Shannon index and extended genetic distances.</p

Dynamics of naphthenic acids and microbial community structures in a membrane bioreactor treating oil sands process-affected water: impacts of supplemented inorganic nitrogen and hydraulic retention time

This study was focused on how different operating conditions affected the biodegradation of naphthenic acids (NAs) and the microbial community architectures in an anoxic-aerobic membrane bioreactor (MBR) for oil sands process-affected water (OSPW) treatment. After 442 days of continuous optimization, a supplemented NH4-N concentration of 25 mg L-1 and a hydraulic retention time (HRT) of 12 h demonstrated the best removal rates of total classical NAs (37.6%) and total oxidized NAs (23.9%). Neither higher HRTs nor higher supplemented NH4-N concentrations resulted in a better overall removal of NAs. In addition, NAs with larger carbon numbers were generally better degraded, whereas higher cyclicity tended to lessen the biodegradability of NAs. MiSeq sequencing analysis disclosed that orders under Proteobacteria (i.e., Rhodocyclales, Burkholderiales and Nitrosomonadales), Bacteroidetes (i.e., Cytophagales, [Saprospirales] and Flavobacteriales), and Nitrospirae (i.e., Nitrospirales) were the major microbes over the whole study though their relative abundances varied. The results of this study provide insightful information for future studies and application of biological processes for OSPW treatment on a large scale.</p

Effects of ozone pretreatment and operating conditions on membrane fouling behaviors of an anoxic-aerobic membrane bioreactor for oil sands process-affected water (OSPW) treatment

Two identical anoxic-aerobic membrane bioreactors (MBRs) were operated in parallel for 742 consecutive days for raw and ozonated oil sands process-affected water (OSPW) treatment. The MBRs not only substantially degraded OSPW classical and oxidized NAs, but also demonstrated outstanding membrane fouling control performance (the MBR receiving raw OSPW experienced its first severe fouling with a transmembrane pressure (TMP) of −35 kPa on Day 433). The mild ozonation (30 mg O 3 /L) pretreatment of OSPW remarkably enhanced OSPW NA degradation, and improved the MBR's fouling control in terms of prolonged long-term slow TMP growth phase and reduced TMP jump frequency. Ozonation substantially altered the feed water organic composition, reshaped the microbial community (e.g., reduced growth of extracellular polymeric substances (EPS) producers and biofilm formation facilitators), and lowered EPS production and EPS protein/polysaccharides (PN/PS) ratio, consequently leading to the better fouling control. Examination on fouling behaviors at different HRTs of the raw OSPW MBR indicates that HRT also played a role in determining the dominating fouling mechanism during the sharp TMP rise phase. Therefore, the results of this study suggest that the low-dose ozone pretreatment is a good option to enhance organic contaminant degradation and alleviate membrane fouling in the MBR for OSPW treatment.</p

Treatment of raw and ozonated oil sands process-affected water under decoupled denitrifying anoxic and nitrifying aerobic conditions: a comparative study

Batch experiments were performed to evaluate biodegradation of raw and ozonated oil sands process-affected water (OSPW) under denitrifying anoxic and nitrifying aerobic conditions for 33 days. The results showed both the anoxic and aerobic conditions are effective in degrading OSPW classical and oxidized naphthenic acids (NAs) with the aerobic conditions demonstrating higher removal efficiency. The reactors under nitrifying aerobic condition reduced the total classical NAs of raw OSPW by 69.1 %, with better efficiency for species of higher hydrophobicity. Compared with conventional aerobic reactor, nitrifying aerobic condition substantially shortened the NA degradation half-life to 16 days. The mild-dose ozonation remarkably accelerated the subsequent aerobic biodegradation of classical NAs within the first 14 days, especially for those with long carbon chains. Moreover, the ozone pretreatment enhanced the biological removal of OSPW classical NAs by leaving a considerably lower final residual concentration of 10.4 mg/L under anoxic conditions, and 5.7 mg/L under aerobic conditions. The combination of ozonation and nitrifying aerobic biodegradation removed total classical NAs by 76.5 % and total oxy-NAs (O3–O6) by 23.6 %. 454 Pyrosequencing revealed that microbial species capable of degrading recalcitrant hydrocarbons were dominant in all reactors. The most abundant genus in the raw and ozonated anoxic reactors was Thauera (~56 % in the raw OSPW anoxic reactor, and ~65 % in the ozonated OSPW anoxic reactor); whereas Rhodanobacter (~40 %) and Pseudomonas (~40 %) dominated the raw and ozonated aerobic reactors, respectively. Therefore, the combination of mild-dose ozone pretreatment and subsequent biological process could be a competent choice for OSPW treatment.</p

Treatment of oil sands process-affected water using membrane bioreactor coupled with ozonation: A comparative study

The huge amount of toxic oil sands process-affected water (OSPW) stored in northern Alberta is of great concern to the public health and aquatic life. Therefore, cost-effective and more efficient approaches for OSPW treatment are urgently needed. In this study, mild ozonation followed by a modified Luzack-Ettinger membrane bioreactor (MLE-MBR) were employed for the treatment of OSPW. It was shown that with a utilized ozone dose of 30 mg/L, 42.5-47.4% of classical naphthenic acids (NAs) were removed with toxicity reduction towards Vibrio fischeri. While ozonation targeted the heteroatomic NAs and classical NAs with high cyclicity and carbon number, MBR showed its advantages in removing oxidized NAs and classical NAs with less hydrogen deficiency. With excellent nitrification and denitrification performance, MBR achieved the removal of 46% for classical NAs, indicating the success of sludge acclimation in the MBR. Thauera became the most dominating bacterial genus in MBR, revealing its potentials in OSPW treatment. Compared with MBR treating raw OSPW, ozone pretreatment contributed to improved denitrification and NA removal in MBR. Moreover, it altered microbial community structure, thus delaying the occurrence of membrane fouling. During 426 days of continuous operation, no severe membrane fouling was observed as the transmembrane pressure (TMP) of the MLE-MBR never exceeded -12 kPa. With a reduction of classical NAs by around 70%, our results indicated that the MLE-MBR coupled with ozonation, is a promising approach for removing recalcitrant organics in OSPW.</p