Effect of hydraulic retention time on pollutants removal from real ship sewage treatment via a pilot-scale air-lift multilevel circulation membrane bioreactor

An integrated process for struvite recovery and nutrient removal from ship domestic sewage

Marine pollution caused by the untreated and substandard discharge of ship domestic sewage has received widespread attention. A novel integrated process for struvite recovery and nutrient removal from ship domestic sewage (SRNR-SDS) based on seawater magnesium source was developed in this study. Removal efficiencies of the total nitrogen (TN) and total phosphorus (TP) for the activated sludge unit in SRNR-SDS process were approximately 67.61% and 41.35%, respectively, under the salinity of 7.85 g/L. The coupling-induced struvite crystallization unit significantly improved the removal efficiency of TN and TP, and the scanning electron microscopy and X-ray diffraction demonstrated that magnesium ammonium phosphate (MAP) crystals were successfully formed on the surface of zeolite. The SRNR-SDS process had an ideal performance for pollutant removal and MAP recovery under the optimal hydraulic retention time of 20 h. The effluent concentrations of COD, NH₄⁺-N, TN and TP in SRNR-SDS process were approximately 34.73 mg/L, 4.31 mg/L, 10.07 mg/L and 0.23 mg/L, respectively, which meet the Chinese and international ship sewage discharge standards. SRNR-SDS process has obvious environmental, social and economic benefits, which could save 6.20%∼57.14% of the operation cost of ship domestic sewage treatment via MAP recovery. The results could provide theoretical and technical support for the development and application of ship sewage treatment process with the functions of pollutant removal and resource recovery.

Mechanism of HMBR in Reducing Membrane Fouling under Different SRT: Effect of Sludge Load on Microbial Properties

Extracellular polymeric substances (EPS) are the main causative agents of membrane fouling, and the use of a hybrid membrane bioreactor (HMBR) can mitigate this by reducing the EPS content. Four bench scale sets of HMBRs were used simultaneously to treat domestic wastewater. The effect of sludge retention times (SRT) on membrane fouling in HMBRs and the underlying mechanism were investigated by comparing and analyzing the changes in sludge load, microbial characteristics, EPS distribution characteristics, and transmembrane pressure under different SRTs. Results revealed that, among the four SRTs (10 d, 20 d, 30 d, and 60 d), the best removal rates of chemical oxygen demand and total nitrogen were observed for an SRT of 30 d, with average removal rates of 95.0% and 57.1%, respectively. The best results for ammonia nitrogen and total phosphorus removal were observed at an SRT of 20 d, with average removal rates of 84.3% and 99.5%, respectively. SRT can affect sludge load by altering the biomass, which significantly impacts the microbial communities. The highest microbial diversity was observed at an SRT of 30 d (with a BOD sludge load of 0.0310 kg/kg∙d), with Sphingobacteriales exhibiting the highest relative abundance at 19.6%. At this SRT setting, the microorganisms produced the least amount of soluble EPS and loosely bond EPS by metabolism, 3.41 mg/g and 4.52 mg/g, respectively. Owing to the reduced EPS content, membrane fouling was effectively controlled and the membrane module working cycle was effectively enhanced up to 99 d, the longest duration among the four SRTs.

Wastewater treatment for ships experiencing large temperature changes： the activated sludge/membrane-biofilm reactor

A particular challenge to treatment systems for ship wastewater comes from low and variable temperatures. We evaluated the temperature response (35-15 °C) of a novel biological treatment system involving activated sludge followed by a membrane-biofilm reactor: the activated sludge/membrane-biofilm reactor (AS-ABfMemR). In this study, a pilot-scale AS-ABfMemR achieved over 96% chemical oxygen demand (COD) and 94% total nitrogen (TN) removal from a ship wastewater (550-960 mgCOD·L^-1 and 52-77 mgTN·L^-1) with a continuous operation with a hydraulic retention time of 12 h at 25 °C. The effluent COD and TN concentrations met IMO discharge standards at temperatures as low as 17 °C, which reduced the energy consumption for wastewater heating. The COD and TN removals of the biofilm stage became important (up to 34% and 35%, respectively) at low temperatures, and this compensated for the deterioration in performance of the aerobic sludge. The genus Azospira dominated in the biofilm's denitrification removal for TN at low temperature. In addition, the buildup of trans-membrane pressure was so slow that backwashing was not needed over the 90 days of continuous operation. These conclusions indicate that the pilot-scale AS-ABfMemR technology is an effective way for real ship sewage treatment under temperature variations.

Marine environment and maritime safety assessment using Port State Control database

Port State Control (PSC) is the inspection of foreign ships in national ports assists in the removal of substandard ship commerce from the global sea and ensures that no ship poses a threat to maritime safety and the marine environment. When a clear ground is discovered during an inspection, the inspector has the authority to detain the ship until the flaws are corrected in order to assure safety and reduce pollution hazards. This paper adopted a traditional literature review method using the selected six (6) years data from the inspections conducted by maritime authorities from 2016 to 2021 and incorporate with qualitative and quantitative analysis to ascertain the influence of each risk factor on the number of arrests, including the relationship between risk factors and the type of detain deficiency, which is a critical part of the study. This study's findings provide important insights into how to facilitate an effective way in selecting the ship to be inspected, followed by identifying the ship's risk profile and designing the inspection area, which plays a critical role in assisting the inspector in terms of time efficient and effective inspection (especially for the ships, which have a short duration at berth) during inspection to further strengthen maritime safety, ship's safety, seafarers' health and marine environmental protection.

Environmental impact, treatment technology and monitoring system of ship domestic sewage: A review

Marine pollution caused by the substandard discharge of domestic sewage from ships has received considerable attention in recent years. Thus, the research and application of efficient treatment and supervision system of domestic ship sewage are matters of considerable interest in marine pollution prevention. The environmental impacts of black and grey water on marine and river environments were reviewed to emphasize the urgency and importance of sewage treatment. Development and changes of emission indexes revealed the emphasis on marine environmental protection and domestic sewage discharge. Based on summarizing the difficulties of high salinity, high organic load and poor stability in ship sewage treatment, the technologies of physical-, chemical- and biochemical-based processing were reviewed. Case study of online monitoring system was displayed to provide research trends. The challenges and future perspectives were also provided to promote supervision and disposal of domestic sewage from ships.

Microbial community structure analysis in a hybrid membrane bioreactor via high-throughput sequencing

Compared to the suspended culture (sludge) of a conventional bioreactor, hybrid membrane bioreactors (HMBRs) are more effective at removing pollutants owing to the addition of fillers addition of fillers that facilitate biofilm formation. However, the microbial community structure and composition in an HMBR remain unclear. We ran three laboratory-scale HMBRs at room temperature under different sludge retention times (SRTs; 10 d, 20 d, and 30 d) to compare the microbial diversity and community structure among the membrane surface, suspended filler surface, and mixed liquor using high-throughput sequencing. The results showed that SRT can markedly affect microbial community structure in the HMBR, and different trends appeared in the three functional units. The largest number of mutual operational taxonomic units was found in the activated sludge mixture and suspended carrier with an SRT of 20 d and 30 d. Species belonging to Proteobacteria in the 10 d SRT group had the greatest contribution to between-group differences. A longer SRT could mitigate membrane fouling by decreasing the relative abundance of Thauera and Sphaerotilus attached on the membrane surface. Comamonadaceae, a family of denitrifying bacteria, offer high denitrification potential for bioreactors operating under a long SRT.

Nanoparticles Synergistic Effect with Various Substrate Pretreatment and their Comparison on Biogas Production from Algae Waste

Algae waste is one of the potential substrates for biogas and biohydrogen production and can comprehend multiple benefits of waste treatment and resource utilization. In view of the key bottlenecks such as low substrate degradation rate and poor productivity of algae waste production process, this study analyzes the combined effect of two metallic and metallic oxide nanoparticles with different substrate pretreatment methods (autoclave, ultrasonic, and microwave methods) to investigate the effect of anaerobic digestion of green algae (Enteromorpha). The results showed that out of the three pretreatment methods, microwave pretreatment and nanoparticles' synergistic effect significantly increases biogas production. The microbial community composition at the phylum level was analyzed. It was observed that the Firmicutes were most abundant across all samples. The relative abundance of Firmicutes for control, Ni NPs + MW, Co NPs + MW, and Fe3O4 NPs + MW groups were 51.78, 70.37, 75.77, and 83.93%,      respectively. The second most abundant was of Bacteroidetes that also contributes to hydrogen production. This relatively high abundance of Firmicutes and Bacteroidetes promises its potential applications in a hydrogen production facility. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Implementation of environmental surveillance for SARS-CoV-2 virus to support public health decisions: Opportunities and challenges

Analysing wastewater can be used to track infectious disease agents that are shed via stool and urine. Sewage surveillance of SARS-CoV-2 has been suggested as a tool to determine the extent of COVID-19 in cities and serve as an early warning for (re-)emergence of SARS-CoV-2 circulation in communities. The focus of this review is on the strength of evidence, opportunities and challenges for the application of sewage surveillance to inform public health decision making. Considerations for undertaking sampling programs are reviewed including sampling sites, strategies, sample transport, storage and quantification methods; together with the approach and evidence base for quantifying prevalence of infection from measured wastewater concentration. Published SARS-CoV-2 sewage surveillance studies (11 peer reviewed and 10 preprints) were reviewed to demonstrate the current status of implementation to support public health decisions. Although being very promising, a number of areas were identified requiring additional research to further strengthen this approach and take full advantage of its potential. In particular, design of adequate sampling strategies, spatial and temporal resolution of sampling, sample storage, replicate sampling and analysis, controls for the molecular methods used for the quantification of SARS-CoV-2 RNA in wastewater. The use of appropriate prevalence data and methods to correlate or even translate SARS-CoV-2 concentrations in wastewater to prevalence of virus shedders in the population is discussed.

A sustainability anti-infective pharmaceutical wastewater treatment technology: multi-stage vertical variable diameter membrane bioreactor with DO online controlling

The proper choice of dissolved oxygen (DO) is important in aerobic treatment. In this paper, a multi-stage vertical variable diameter membrane bioreactor was developed to treat pharmaceutical wastewater containing 6-APA and ceftriaxone sodium. In the 180 days of operation, the performance of COD, BOD₅, 6-APA, ceftriaxone sodium removal, sludge index, and microbial enzyme activity under different DOs (from 0.5 to 6.0 mg/L) were investigated. The results showed that the optimal range of DO was 1.5-2.1 mg/L, and the highest removal rates of COD and BOD₅ were observed 87.3%±2.4% and 95.3%±1.8%, the corresponding effluent COD and BOD₅ were 189 mg/L and 24 mg/L, respectively. To reduce the energy consumption and ensure stability of DO in the reactor, a control strategy based on an improved differential evolution BP fuzzy neural network was built and found that the performance and cost of the controlled DO were improved effectively than that of uncontrolled DO.

Social Cost Benefit Analysis of Port Handling Plans for Annex IV waste of MARPOL: A Case Study in Las Palmas Port

This paper analyzes the effectiveness of Directive (EU) 2019/883 from the social interest perspective. To achieve this aim, it assesses the performance of the sewage treatment plan (Annex IV of MARPOL) in Las Palmas Port and the accomplishment of the Cost Recovery System. This involves reviewing the mandatory fees for landing the sewage in the port, the sewage treatment costs and the environmental impact of the treated effluent from the vessels (environmental benefits) and addressing technical difficulties in order to meet the normative standard required from the vessels’ sewage in the framework of Las Palmas Port. Through a cost–benefit analysis not only the current protocol for the reception and treatment of Annex IV waste in the port is assessed, but also alternative waste treatment plans (sewage routes) are discussed in terms of social interest. The results of the paper show that only when the treated sewage is reused are the costs assumed to implement the directive overtaken by the benefits gained from complying with it. Consequently, the port authorities should address their efforts in this direction, as should the policy makers, who should integrate in the international normative the collaboration of the on-board sewage treatment plants to meet the PPP (Polluter Pays Principle).

Box-Behnken response surface approach to identify factors affecting membrane fouling in a hybrid membrane bioreactor treating domestic sewage

The effect of hydraulic retention time (HRT) and sludge retention time (SRT) on extracellular polymer substrate (EPS) content and resistance of a hybrid membrane bioreactor (HMBR) treating domestic sewage was analyzed by Box-Behnken response surface methodology. The quadratic response surface model demonstrated significant effects of both HRT and SRT on EPS content (both P value < 0.05), SRT on membrane resistance (P value = 0.0119), and their interaction was significant (P value = 0.0273) for EPS but not membrane resistance (P value = 0.0609). Model optimization indicates that the optimal conditions for the HMBR to control membrane fouling were an HRT of 10 h and SRT of 30 days. Under these optimal conditions, both the EPS content and the predicted membrane resistance closely matched the actual average value with the error about 8%. Thus, the feasibility of applying response surface methodology to an HMBR for treating domestic sewage was demonstrated. According to the detection result of the three-dimensional fluorescence (excitation-emission matrix), humic acid-like and fulvic acid-like substances gain much higher levels in the suspended carriers than those in the membrane and sludge, suggesting that these are key components of the membrane pollutants. Graphical abstract .

Influence of salinity on the biological treatment of domestic ship sewage using an air-lift multilevel circulation membrane reactor

Recently, strict standards for ship domestic sewage discharge have been implemented by the International Maritime Organization (IMO). The high salinity of ship sewage was considered a key factor influencing the removal efficiency of ship sewage treatment systems. In the present study, the salinity effect on the removal of chemical oxygen demand (COD) and ammonia nitrogen (NH₄⁺-N) from ship domestic sewage was investigated by using a novel air-lift multilevel circulation membrane reactor (AMCMBR). Enzyme activity analysis and wavelet neural network (WNN) models were built to determine the mechanisms of the process. The experimental results indicate that high salinity levels (> 21 g/L) had a negative impact on COD and NH₄⁺-N removal efficiencies, and low saline concentrations (≤ 21 g/L) caused a negligible effect. The COD and NH₄-N removal efficiencies were 84% and 97%, respectively, at a salinity of 21 g/L, which were higher than those at low salinities (i.e., 7 g/L and 14 g/L). Invertase and nitrate reductase had a close relationship with removal performance, and they can be considered important indicators reflecting the operation effort under saline environments. With high predictive accuracies, the constructed WNN models simulated the complex COD and NH₄⁺-N removal processes well under different saline concentrations, ensuring the long-term stable operation of the AMCMBR under different salinities.