Comparative study of biological nutrient removal (BNR) processes with sedimentation and membrane-based separation

Fast detection method for prostate cancer cells based on an integrated ResNet50 and YoloV5 framework

PURPOSE

To propose a fast detection method for prostate cancer abnormal cells based on deep learning. The purpose of this method is to quickly and accurately locate and identify abnormal cells, so as to improve the efficiency of prostate precancerous screening and promote the application and popularization of prostate cancer cell assisted screening technology.

METHOD

The method includes two stages: preliminary screening of abnormal cell images and accurate identification of abnormal cells. In the preliminary screening stage of abnormal cell images, ResNet50 model is used as the image classification network to judge whether the local area contains cell clusters. In the another stage, YoloV5 model is used as the target detection network to locate and recognize abnormal cells in the image containing cell clusters.

RESULTS

This detection method aims at the pathological cell images obtained by the membrane method. And the double stage models proposed in this paper are compared with the single stage model method using only the target detection model. The results show that through the image classification network based on deep learning, we can first judge whether there are abnormal cells in the local area. If there are abnormal cells, we can further use the target detection method based on candidate box for analysis, which can reduce the reasoning time by 50% and improve the efficiency of abnormal cell detection under the condition of losing a small amount of accuracy and slightly increasing the complexity of the model.

CONCLUSION

This study proposes a fast detection method for prostate cancer abnormal cells based on deep learning, which can greatly shorten the reasoning time and improve the detection speed. It is able to improve the efficiency of prostate precancerous screening.

Modeling, simulation and control of biological and chemical P-removal processes for membrane bioreactors (MBRs) from lab to full-scale applications: State of the art

Phosphorus (P) removal from the domestic wastewater is required to counter the eutrophication in receiving water bodies and is mandated by the regulatory frameworks in several countries with discharge limits within 1-2mgPL-1. Operating at higher sludge retention time (SRT) and higher biomass concentration than the conventional activated sludge process (CASP), membrane bioreactors (MBRs) are able to remove 70-98% phosphorus without addition of coagulant. In full-scale facilities, enhanced biological phosphorus removal (EBPR) is assisted by the addition of metal coagulant to ensure >95% P-removal. MBRs are successfully used for super-large-scale wastewater treatment facilities (capacity >100,000 m3d-1). This paper documents the knowledge of P-removal modeling from lab to full-scale submerged MBRs and assesses the existing mathematical models for P-removal from domestic wastewater. There are still limited studies involving integrated modeling of the MBRs (full/super large-scale), considering the complex interactions among biology, chemical addition, filtration, and fouling. This paper analyses the design configurations and the parameters affecting the biological and chemical P-removal in MBRs to understand the P-removal process sensitivity and their implications for the modeling studies. Furthermore, it thoroughly reviews the applications of bio-kinetic and chemical precipitation models to MBRs for assessing their effectiveness with default stoichiometric and kinetic parameters and the extent to which these parameters have been calibrated/adjusted to simulate the P-removal successfully. It also presents a brief overview and comparison of seven (7) chemical precipitation models, along with a quick comparison of commercially available simulators. In addition to advantages associated with chemical precipitation for P-removal, its role in changing the relative abundance of the microbial community responsible for P-removal and denitrification and the controversial role in fouling mitigation/increase are discussed. Lastly, it encompasses several coagulant dosing control systems and their applications in the pilot to full-scale facilities to save coagulants and optimize the P-removal performance.

Comparative study on treatment performance, membrane fouling, and microbial community profile between conventional and hybrid sequencing batch membrane bioreactors for municipal wastewater treatment

A sequencing batch conventional membrane bioreactor (SB-CMBR) and sequencing batch hybrid membrane bioreactor (SB-HMBR) were operated in parallel under two different hydraulic retention times (HRTs) (namely 12 h and 6 h), and their chemical oxygen demand (COD) and nutrient removal performance, membrane fouling behavior, and microbial community characteristics were compared. Both systems exhibited high organic matter (> 95%) and ammonium (> 98%) removal performance regardless of the HRT applied. As the HRT was reduced from 12 to 6 h, total nitrogen removal slightly increased in both reactors, being higher in the carrier-based MBR, where anoxic zones may have been established within the biofilm. Conversely, total phosphorus removal improved only in the SB-CMBR at the shorter HRT. Moreover, activity batch assays have shown a faster P uptake rate in the SB-CMBR than in the SB-HMBR, a result likely associated with the lower relative abundance of phosphate-accumulating organisms in both adhered and suspended biomass fractions in the hybrid MBR. The results also revealed that more pronounced increases in the transmembrane pressure and, consequently, in the membrane fouling rate at higher COD loading rates were observed in the SB-CMBR, where the soluble microbial products (proteins, polysaccharides, and especially, transparent exopolymer particles), supernatant turbidity, and filamentous bacteria were more significant. Overall, as compared to the conventional MBR, the plastic media-based SB-HMBR showed a lower fouling propensity at all hydraulic conditions tested.

Transcriptomics investigation of thyroid hormone disruption in the olfactory system of the Rana [Lithobates] catesbeiana tadpole

Thyroid hormones (THs) regulate vertebrate growth, development, and metabolism. Despite their importance, there is a need for effective detection of TH-disruption by endocrine disrupting chemicals (EDCs). The frog olfactory system substantially remodels during TH-dependent metamorphosis and the objective of the present study is to examine olfactory system gene expression for TH biomarkers that can evaluate the biological effects of complex mixtures such as municipal wastewater. We first examine classic TH-response gene transcripts using reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) in the olfactory epithelium (OE) and olfactory bulb (OB) of premetamorphic Rana (Lithobates) catesbeiana tadpoles after 48 h exposure to biologically-relevant concentrations of the THs, 3,5,3'-triiodothyronine (T3) and L-thyroxine (T4), or 17-beta estradiol (E2); a hormone that can crosstalk with THs. As the OE was particularly sensitive to THs, further RNA-seq analysis found >30,000 TH-responsive contigs. In contrast, E2 affected 267 contigs of which only 57 overlapped with THs suggesting that E2 has limited effect on the OE at this developmental phase. Gene ontology enrichment analyses identified sensory perception and nucleoside diphosphate phosphorylation as the top affected terms for THs and E2, respectively. Using classic and additional RNA-seq-derived TH-response gene transcripts, we queried TH-disrupting activity in municipal wastewater effluent from two different treatment systems: anaerobic membrane bioreactor (AnMBR) and membrane enhanced biological phosphorous removal (MEBPR). While we observed physical EDC removal in both systems, some TH disruption activity was retained in the effluents. This work lays an important foundation for linking TH-dependent gene expression with olfactory system function in amphibians.

Effect of solids retention time on nitrogen and phosphorus removal from municipal wastewater in a sequencing batch membrane bioreactor

This study evaluated the removal of organic matter, nitrogen and phosphate from a municipal wastewater in a sequencing batch membrane bioreactor (SBMBR) operated at different solids retention times (SRTs) and subjected to different aeration profiles. The results demonstrated that SRT reduction from 80 to 20 d had a negligible effect on chemical oxygen demand (COD) removal and only a slight negative effect on nitrification. COD removal efficiency remained stable at 97%, whereas ammonium removal decreased from 99% to 97%. The total nitrogen removal efficiency was improved by SRT reduction, increasing from 80% to 86%. Although the total phosphorus (TP) removal was not significantly affected by the SRT reduction, ranging from 40-49%, the P-release and P-uptake processes were observed to increase as the SRT was reduced. The implementation of a pre-aeration phase in the SBMBR operating cycle allowed a higher TP removal performance, which reached up to 76%. Batch tests suggested that the fraction of phosphate removed anoxically from the total (anoxic + aerobic) phosphate removal decreased with the SRT reduction.

Production and characterization of foam in the anoxic zone of a membrane-enhanced biological phosphorus removal process

A pilot-scale membrane-enhanced biological phosphorus removal process accumulated substantial quantities of stable foam on the surface of the anoxic zone. The foam contained 4 to 6% dry matter, with specific nitrogen and phosphorus contents that were similar to those of the underlying anoxic zone mixed liquor. Kinetic studies demonstrated that the specific rate of phosphorus release from the foam was only 25 to 30% of that observed with mixed liquor from the aerobic zone. Molecular techniques demonstrated that the calculated similarity of the microbial communities in the foam and the underlying mixed liquor was approximately 80%, with two phylotypes (Gordonia amarae and Microthrix parvicella) being uniquely enriched in the foam and one phylotype (Epistylis sp.) more abundant in the underlying mixed liquor. The production of foam was demonstrated to be a consistent phenomenon that depended on the concentration of the suspended solids in the bioreactor.

Pilot-scale experience with biological nutrient removal and biomass yield reduction in a liquid-solid circulating fluidized bed bioreactor

A pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor was developed at the Adelaide Pollution Control Plant, London, Ontario, Canada, to study its commercial viability for biological nutrient removal. Lava rock particles of 600 microm were used as a biomass carrier media. The LSCFB removed approximately 90% organic, 80% nitrogen, and 70% phosphorus at loading rates of 4.12 kg COD/m3 x d, 0.26 kg N/m3 x d, and 0.052 kg P/m3 x d, and an empty bed contact time of 1.5 hours. Effluent characterized by < 1.0 mg NH4-N/L, < 5.0 mg NO3-N/ L, < 1.0 mg PO4-P/L, < 10 mg TN/L, < 10 mg SBOD/L, and 10 to 15 mg volatile suspended solids (VSS)/L can easily meet the criteria for nonpotable reuse of treated wastewater. The system removed nutrients without using any chemicals, and the secondary clarifier removed suspended solids removal without chemicals. A significant reduction (approximately 75%) in biomass yield to 0.12 to 0.16 g VSS/g chemical oxygen demand (COD) was observed, primarily because of long biological solids retention time (SRT) of 20 to 39 days and a combination of anoxic and aerobic COD consumption.

Biological nutrient removal in an MBR treating municipal wastewater with special focus on biological phosphorus removal

The performance of an MBR pilot plant for biological nutrient removal was evaluated during 210days of operation. The set point values for the internal recycles were determined in advance with the use of an optimisation spreadsheet based on the ASM2d model to optimise the simultaneous removal of C, N and P. The biological nutrient removal (BNR) efficiencies were high from the start of operation with COD and N removal efficiencies of 92+/-6% and 89+/-7, respectively. During the course of the experiment P removal efficiencies increased and finally a P-removal efficiency of 92% was achieved. The activity of poly-phosphate accumulating organisms (PAOs) and denitrifying poly-phosphate accumulating organisms (DPAOs) increased and the specific phosphate accumulation rates after 150days of operation amounted to 13.6mgPg(-1)VSSh(-1) and 5.6mgPg(-1)VSSh(-1), for PAOs and DPAOs, respectively.

Effect of membranes on refractory dissolved organic nitrogen

A 500-day comparative study with a novel membrane bioreactor (NMBR), anaerobic-anoxic-aerobic (A2/O) process, and University of Cape Town-adapted MBR (UMBR) investigated the effect of membrane on effluent dissolved organic nitrogen (efDON) using synthetic (SWW) and municipal wastewater (MWW). The runs, comparing an NMBR and A2/O process, indicated 0.3 mg/L lower efDON in the former than the latter. However, NMBR and UMBR achieved similar efDON quality, with an average of 0.8 mg/L, and the DON reduction by membrane averaged 0.4 mg/L, while the A2/O efDON was slightly higher than DON in the aeration tank, by 0.08 mg/L, on average. The efDON during the MWW run increased by as much as 0.8 mg/L compared with the SWW run. The efDON is a component of a protein found in soluble microbial products, and it followed a cyclical temporal pattern during the runs. Membrane fouling propensity increased the efDON. This study presents evidence that membranes are effective in reducing efDON.

Comparative performance of A2/O and a novel membrane-bioreactor-based process for biological nitrogen and phosphorus removal

The comparison between a novel membrane bioreactor (MBR) system and a conventional anaerobic-anoxic-aerobic (A2/O) system was conducted using synthetic wastewater (SWW) and municipal wastewater (MWW). Each system was operated at an overall hydraulic retention time of 8 hours and solids retention time of 10 days. The MBR exhibited better overall system performance than the A2/O system, in terms of phosphorus removal. Nitrogen removal efficiencies were close in the two systems at 73 to 74% in both runs, while phosphorus removal efficiencies were 96 and 74% (SWW run) and 80 and 75% (MWW run), for the MBR and A2/O, respectively. Effluent soluble chemical oxygen demand (COD) was less than 15 mg/L in the two systems during both runs. Phosphorus uptake by denitrifying phosphate-accumulating organisms accounted for 49% of the total uptake in the MBR compared with 33% in the A2/O during the SWW run. The dynamic test clearly showed that the MBR had better denitrification capacity than the A2/O system. The MWW run indicated that MBR ferments particulate COD better than A2/ O. The effect of the intermediate clarifier on MBR phosphorus removal was significant, with phosphorus uptake of 0.16 g/d in the SWW run and phosphorus release of 0.08 g/d in the MWW run, thus enhancing thetotal phosphorus removal in both cases.

Phosphorus fractionation in membrane-assisted biological nutrient removal processes

A comparison between a patented novel membrane bioreactor (NMBR) and conventional University of Cape Town adapted MBR (UMBR) was conducted using two different municipal wastewaters at a total bioreactor hydraulic retention time of 6h and sludge retention time of 10d. Total nitrogen removal efficiencies were 73-80% and 70-77% for the NMBR and UMBR, respectively, with 1-1.7 mgL(-1) lower effluent nitrates in the NMBR. The average effluent P in the NMBR and UMBR were 0.5 and 0.8 mgL(-1), respectively. P uptake by denitrifying phosphate accumulating organisms (DPAO) accounted for 37-40% of the total uptake in both systems and DPAOs were 40% of PAO. Sludge P fractionation substantiated that poly-P content increased from 27-37% to 57-59% of the total phosphorus, with P increasing from around 3% to 6% by weight upon the supplementation of the wastewater volatile fatty acids.

Enhanced biological nutrient removal using MUCT-MBR system

Biological nutrient removal was investigated in a combined modified University of Cape Town and membrane bioreactor system. When the influent nutrient mass ratio (COD/TN/TP) was 28.5/5.1/1 to 28.5/7.2/1, average removal efficiencies of COD, TN and TP were 90%, 81.6%, 75.2%. Obvious denitrifying phosphorus removal occurred with C/N ratio 3.98. When nitrite was the main electron acceptor, the ratio of denitrifying phosphate uptake to the total phosphate uptake were 99.8% and the sludge yield was 0.28kg VSS/kg COD; when nitrate was the main electron acceptor, the ratio was 92% and the yield was 0.32kg VSS/kg COD. In case of nitrite, the system not only kept TP and TN removal at 89.1% and 82.2%, but also ensured less sludge production. Batch tests showed that the proportion of denitrifying phosphorus-accumulating organisms in the total phosphorus-accumulating organisms in the system was higher than 80%.

Comparison of nitrification rates in conventional and membrane-assisted biological nutrient removal processes

A membrane-assisted and a conventional activated sludge system, both operated in an enhanced biological phosphorus removal (EBPR) mode and under identical operating conditions, were studied to investigate the effect of the membrane solids-liquid separation on nitrification activity. Both the membrane EBPR (MEBPR) and conventional EBPR (CEBPR) processes achieved stable and complete removal of ammonium-nitrogen from the influent wastewater. However, when the intrinsic nitrification activity was assessed in offline batch tests, the CEBPR mixed liquor exhibited 15 to 75% greater nitrification potential than the MEBPR counterpart. These results were further validated by monitoring nitrification rates of conventional mixed liquor as it evolved toward a membrane mixed liquor. It was also demonstrated that the larger aerobic mass fraction of the MEBPR system could not be the only factor influencing the reduced intrinsic nitrification rate. The present study strongly suggests that the presence of a membrane solids-liquid separation per se may be sufficient to alter the nitrification kinetics of an EBPR mixed liquor and that this possibility should be considered in arriving at an appropriate process design.

Biological nutrient removal in a small-scale MBR treating household wastewater

The biological nutrient-removal potential of an on-site Membrane bioreactor (MBR) located in the basement of a four-person house treating domestic wastewater was investigated. The reactor consists of two tanks in series. This treatment plant differs from other conventional MBRs by a highly fluctuating influent water flow and a lack of pretreatment. During the first period, the first reactor was operated as a primary clarifier, resulting in nitrogen and phosphorus removals of 50% and 25%, respectively. Primary sludge production and bad odors in the basement were further disadvantages. When using the first reactor as an anaerobic/anoxic reactor by recycling activated sludge and mixing the first reactor, nitrogen and phosphorus removals of over 90% and 70% were achieved, respectively. By applying a dynamic model of the plant, the return sludge ratio was identified as the most important parameter. With a return sludge ratio of about 1.2, optimal PAO growth and phosphorous removal up to 90% was reached. Since only activated sludge is produced with this operational mode, on-site sludge dewatering is possible. During vacation periods without loading, the Bio-P activity is kept constant if the aeration is reduced to 5-20 min d(-1).

Toward a high-rate enhanced biological phosphorus removal process in a membrane-assisted bioreactor

A membrane enhanced biological phosphorus removal (MEBPR) process was studied to determine the impact of hydraulic retention time (HRT) and solids retention time (SRT) on the removal of chemical oxygen demand (COD), nitrogen, and phosphorus from municipal wastewater. The MEBPR process was capable of delivering complete nitrification independent of the prevailing operating conditions, whereas a significant improvement in COD removal efficiency was observed at longer SRTs. In the absence of carbon-limiting conditions, the MEBPR process was able to achieve low phosphorus concentrations in the effluent at increasingly higher hydraulic loads, with the lowest HRT being 5 hours. The MEBPR process was also able to maintain optimal phosphorus removal when the SRT was increased from 12 to 20 days. However, at higher suspended solids concentrations, a substantial increase was observed in carbon utilization per unit mass of phosphorus removed from the influent. These results offer critical insights to the application of membrane technology for biological nutrient removal systems.