Removal Efficiencies Of TP Research Articles

Recycled aggregates from construction and demolition waste as wetland substrates for pollutant removal

Large amounts of construction and demolition (C&D) waste have been generated due to the rapid urbanization process in China over recent decades. Hence, effective strategies for C&D waste reuse and recycling are urgently needed to reduce the impact of the generation of C&D waste. This work assessed the pollution control efficiency of recycled aggregates from C&D waste as substrates in vertical flow constructed wetlands (VFCWs) and the regeneration capability of these substrates. Six artificial experimental columns loaded with three recycled aggregates, namely, brick (RBA), concrete (RCA), and concrete-brick mixtures (C&B), and three natural aggregates, namely, limestone (LIM), lava rock (LAV), and zeolite (ZEO), were separately used. The results showed that recycled aggregates performed more effectively in terms of TP and COD removal than did natural aggregates, with the highest removal efficiency of 87.1% towards TP achieved by RCA and 74.9% towards COD achieved by C&B. Nemerow pollution index calculation demonstrated that the effluent water quality followed the order of RCA > C&B > RBA > LIM > ZEO > LAV. NH3–N, TP and COD removal efficiencies of 51.3%, 51.0% and 58.9%, respectively, were observed for RCA after in situ regeneration. The highest NH3–N and TP removal efficiencies were 54.7% and 84.8%, respectively, for RCA by aeration and NaOH washing, respectively, after four adsorption-desorption runs of ectopic regeneration. However, chemical regeneration of RCA and LIM severely destroyed the substrate structure over physical regeneration. Unfortunately, a low temperature led to a poor removal of TN in all systems, and the recycled aggregates from C&D waste were less resistant to impact than were the natural aggregates. Life cycle cost analysis showed that RCA as a substrate reduces the cost of wetland construction. This work provides a systematic comparison of recycled aggregates and natural aggregates as substrates in VFCWs in regard to their purification ability, regeneration methods and economic cost.

Pilot-scale constructed bypass channel for urban river restoration: the remedial efficiency and the variance in biodiversity.

Like the blood vessels of the cities, urban rivers play a significant role on maintaining the cities' sustainable development. In addition to the prevention of pollutants discharge and improving the river water quality, the restoration of the urban rivers' ecosystem should be well concerned. To fill this gap, a pilot-scale study with constructed bypass channel (CBC) was conducted. The pollutants reduction by the aquatic plants of the CBC was evaluated, and the similarities/differences of the aquatic biodiversity between the CBC and the natural rivers were analyzed. The results indicated that the mean removal efficiency of TP, NH3-N, TN, and COD by the CBC was 66%, 60%, 52%, and 36%, respectively. Chlorophyta, Bacillariophyta, and Cyanophyta were the dominant phytoplankton phyla in the CBC which was in accordance with the studies conducted in the Dongjiang River and the Pearl River. During the study period of about 6 months, the population density and the biomass of the phytoplankton and the zooplankton increased over time. The quality of the influent dominated the aquatic organisms' diversity of the CBC. N-element dominated not only the phytoplankton variability, but also the bacterial species of the CBC. The timber pile and the submerged plant root soil were more suitable for the growth of the functional bacteria; thus, the construction of the river restoration infrastructures should avoid using large-scale cement materials. Overall, the study would improve the understanding of urban river restoration practice and provide guidance for future restoration practice especially from the aquatic ecological perspectives.

Intensification of brewery wastewater purification integrated with CO2 fixation via microalgae co-cultivation

Microalgae has presented significant potential in wastewater and flue gas purification process. In the present work, co-cultivation of Scenedesmus sp. 336, Chlorella sorokiniana UTEX1602 and Chlorella sp. L166 were investigated to achieve the target of simultaneous biomass accumulation, wastewater treatment and biological carbon fixation. The experimental results showed that when the mixture ratio of Scenedesmus sp. 336 and Chlorella sorokiniana UTEX1602 was set at 1:1 with the ventilation period of 6 h/d, the cell dry weight could reach 796.89 mg/L. The maximum removal efficiency of NH3-N, TN, TP and COD were 96.22%, 90.57%, 97.37% and 78.83%. The contents of chlorophyll, carotenoid and carbohydrate were 16.05, 9.57 and 30.42 mg/L. The productivity of lipid and protein could achieve 20.82 and 142.12 mg/L. The CO2 fixation rate and carbon removal efficiency were 32.09 mg/L/d and 52.21%, respectively. It could be observed that co-cultivation of different microalgae has the potential to intensity simultaneous wastewater purification and CO2 mitigation.

Development of kinetic models for organic and nutrient removal in biofilm photobioreactor for treatment of domestic wastewater

In this study, four biofilm photobioreactors (BPBRs) were developed for treating septic tank effluent under different hydraulic retention times (HRTs), organic (OLR), nitrogen (NLR) and phosphorus (PLR) loading rates and light intensities. The HRT of 6 days, OLR of 390 mg COD/(m 2 .d), NLR of 90 mg N/(m 2 .d), PLR of 6.1 mg P/(m 2 .d) and light intensity of 150 μ m ol/(m 2 .s) were found to be optimum operating conditions for the BPBRs, resulting in the COD, TN and TP removal efficiencies of 85, 87 and 84 %, respectively, with the effluent quality meeting the discharge standards of Thailand and the ISO 30500. Moreover, the HRTs, OLRs, NLR, PLRs, light intensities as well as daily light integral (DLI) were observed to significantly affect treatment performance and biomass productivity of the BPBRs. Hence, the kinetic models involving these operating parameters including temperature were developed for COD, TN and TP removal in the BPBR system and validated satisfactorily with the data obtained from some previous studies. Application of the developed kinetic models in the design and operation of the BPBR system treating a domestic wastewater was also demonstrated. • Optimal operating conditions of biofilm photobioreactors (BPBRs) were investigated. • The operating parameters significantly affected the performance of the BPBRs. • Kinetic models for organic and nutrient removal were developed and validated. • Application of the developed kinetic models for design of BPBR was demonstrated.

Large-scale hybrid accidental urban wetland for polluted river purification in northern China: Evidence and implications for urban river management

Hybrid accidental urban wetlands (HAUWs) are expected to be a potential low-cost and highly efficient alternative means of minimizing pollutant loads from municipal areas as compared to the single-stage system being used. These unexpected HAUWs are created not through deliberate restoration, but as a result of water infrastructure decisions by local government. However, information on the long-term purification efficiency of large-scale HAUW improving eutrophic urban rivers is largely unexplored. An in-situ HAUW system consisting of a rubber dam, detention pond, accidental urban wetland, and overflow weir was evaluated at the field-scale for the purification of a eutrophic urban river in Zhangjiakou City, Hebei Province. The results for seven months of operation demonstrated that the effluent TP and NH4-N in the HAUW system could comply with the Grade III of Chinese National Surface Water Quality Standards. Average removal efficiencies for TN, NH4-N, NO3-N, TP, and PO4-P in the summer–autumn period of 52.6, 65,8, 56.6, 51.4, 58.2 and 88.3%, respectively, were recorded. These removal efficiencies were 59.4, 61.5, 65.6, 57.1, 59.4 and 65.7% higher than the respective values in the spring period. Furthermore, removal rates of nutrients were highly sensitive to temperature and showed seasonal trends. Further analysis showed that, with the application of the HAUW system, a total of 92.1, 69.5, 57.3, 37.8, 33.2, 12.4, 14.5, 7.3, 3.4% removal of Al, Mn, Cd, Pb, Zn, Ni, Fe, Ni, and As was achieved. Mean removal rates of TN, NH4-N, NO3-N, TP, TDP, PO4-P in the summer–autumn period were 2- 5 times higher than in those recorded in the early spring period. These results suggest that a variety of contaminant elimination mechanisms were offered by the HAUW, including enhanced hydraulic resistance, sedimentation, plant assimilation, microbial biofilm growth on roots’ surface and the HAUW design. Overall, this study demonstrated that the monitored HAUW could be another feature of the urban landscape that could help minimize pollutant loading to surface urban water bodies. This function is especially true in warm periods, in a similar way as natural wetlands or purposely built constructed wetlands. Nonetheless, managing these accidental treatment systems to maximize pollutant dissipation in the long-term would necessitate appropriate management strategies.

Investigation on the improved electrochemical and bio-electrochemical treatment processes of soilless cultivation drainage (SCD)

The soilless crop cultivation under cover generates wastewater called soilless cultivation drainage (SCD), being a nutrient-rich overflow. The average concentration of phosphorus- and nitrogen-based pollutants from soilless tomato cultivation usually ranges from 35.4 to 104.0 mg P/L and from 270.0 to 614.9 mg N/L, respectively. In bio-electrochemical reactors, nitrogen and phosphorus are removed via biological denitrification, electrochemical nitrate reduction, bio-electrochemical reduction, and electrocoagulation. The novelty of this study is due to the use of alternating current (AC), which can both mitigate the corrosion on the anode and solve the issue of insoluble oxide build-up on the cathode. Additionally, and crucially, it promotes bacterial growth and activity. The aim of the present study was to determine (1) the effectiveness of soilless cultivation drainage treatment methods that employ biological and electrochemical processes, with consideration given to (2) the quantity and quality of the produced sludge as a potential nutrient-rich product. The bio-electrochemical reactor proved more effective than the electrochemical one and ensured a high TP and TN removal efficiency exceeding 97% and 66%, respectively. The resulting sludge was rich in such elements as calcium, potassium, carbon, phosphorus, and nitrogen, and as such may serve as a viable alternative to conventional mineral fertilizers.

Application of synthetic and grafted polymeric flocculants in agricultural wastewater treatment

Due to the large amounts of freshwater consumed in Egypt by the agricultural sector that is more than 85% of Egypt share of freshwater in addition to the high concentrations of salts, chemicals and nutrients produced from fertilizers. Reduction of these pollutants concentrations to an acceptable level and breaking the sedimentation stability of colloidal substances and organic particles for reuse for irrigation purposes was associated with the application of biological treatment with coagulants addition. The flocculation process was performed by using polydiallyldimethylammonium chloride (polyDADMAC) and polyacrylamide grafted oatmeal (OAT-g-PAM). The scale-pilot consists of an aeration tank equipped with an air blower, sedimentation tank followed by a filtration stage through 20 cm of pottery scrubs media. To study the performance of synthetic and grafted polymeric flocculants, 3 trials were performed. Activated sludge process without adding any polymeric flocculants was the control trial. In the second trial, polyDADMAC was added with a dose of 5 mg/l. Finally, OAT-g-PAM with a dose of 1.25 mg/l was used in the third trial. The physicochemical properties of agricultural wastewater were measured at the national research center in Cairo. It was found that OAT-g-PAM incorporated with activated sludge process was the most effective in treating agricultural wastewater as it achieved COD, BOD,TKN, TP, and TSS removal efficiency up to 92.29%, 93.13%, 90.64%, 90.46%, and 92.5%, respectively which made it suitable to reuse for agricultural purposes, in addition to its ability to biodegrade, environmentally friendly, and low dosage required compared to polyDADMAC.

Reshaped structure of microbial community within a subsurface flow constructed wetland response to the increased water temperature: Improving low-temperature performance by coupling of water-source heat pump

To evaluate the pollutant removal mechanisms and pathways in traditional constructed wetlands (CWs), and remove its operation bottleneck under low temperature, a co-system was established by coupling a subsurface flow constructed wetland (SFCW) and the water-source heat pump (WSHP) units. Experimental consequence demonstrated that the water temperature had increased significantly, and the mean temperature of influent was 8 ± 3 °C while that of effluent was 15 ± 5 °C. High average removal efficiencies of COD (64.5%), NH3-N (89.5%), NO3-N (90.2%), TN (58%), and TP (93.5%) were achieved in the experimental co-system. Optimal removal efficiency was achieved when pH was 6–7.5 and hydraulic retention time (HRT) was 4 days. Nitrification led to the higher organic pollutants removal efficiency. Meanwhile, it was considered to be due to the significant variation of the microbial community structure after the application of the WSHP units, in which the species richness and community equitability significantly improved. The thermophilic communities grew and reproduced in large numbers. The results also showed the application of co-system was an effective and sustainable strategy for removing diverse pollutants in cold climate.

Semi-batch cultivation of Chlorella sorokiniana AK-1 with dual carriers for the effective treatment of full strength piggery wastewater treatment

In this study, process optimization for the microalgae-based piggery wastewater treatment was carried out by growing Chlorella sorokiniana AK-1 on untreated piggery wastewater with efficient COD/BOD/TN/TP removal and high biomass/protein productivities. Integration of the immobilization carriers (sponge, activated carbon) and semi-batch cultivation resulted in the effective treatment of raw untreated piggery wastewater. With 100% wastewater, 0.2% sponge and 2% activated carbon, the semi-batch cultivation (90% media replacement every 6 days) exhibited a COD, BOD, TN and TP removal efficiency of 95.7%, 99.0%, 94.1% and 96.9%, respectively. The maximal protein content, protein productivity, lutein content, and lutein productivity of the obtained microalgal biomass was 61.1%, 0.48 g/L/d, 4.56 mg/g, and 3.56 mg/L/d, respectively. The characteristics of the treated effluent satisfied Taiwan Piggery Wastewater Discharge Standards (COD < 600 mg/L, BOD < 80 mg/L). This innovative approach demonstrated excellent performance for simultaneous piggery wastewater treatment and microalgal biomass production.

Effects of substrate combinations on greenhouse gas emissions and wastewater treatment performance in vertical subsurface flow constructed wetlands

Climate warming would be generally influenced by the quantity and component of greenhouse gases during the carbon and nitrogen removal in constructed wetlands (CWs). In this study, the impacts of the combinations by walnut shell (organic-rich substrate improving denitrification), manganese (Mn) ore (electron-exchange substrate transferring CH4 to CO2) and activated alumina (phosphorus-adsorption substrate) on global warming potentials (GWPs) were investigated to propose a strategy for both mitigating GWPs and performing well in wastewater treatment. During hybrid CWs, the highest COD and TP removal efficiencies were respectively 89.4% and 98.1% in CWs with the substrate combination of Mn ore and activated alumina, and the highest TN removal efficiency was in CWs with walnut shell and Mn ore. The substrate combination of walnut shell and Mn ore would simultaneously strengthen the nitrification and denitrification process resulting in the lowest N2O flux in CWs. The combinations of Mn ore with walnut shell or activated alumina could significantly decrease the GWPs through promoting the conversion of CH4 to CO2 due to the better redox potential environment favorable for methanotrophs (pmoA) instead of methanogenesis (mcrA) provided by Mn ore. This study provided a feasible way to mitigate climate warming during wastewater treatment in CWs by using substrate combination of Mn ore and walnut shell.

Phosphorus recovery from municipal wastewater with improvement of denitrifying phosphorus uptake based on a novel AAO-SBSPR process

Both synthetic and real municipal wastewaters were used to verify the applicability of a novel AAO-SBSPR (Anaerobic-Anoxic-Oxic/Sequencing Batch Sidestream Phosphorus Recovery) process developed for the phosphorus (P) recovery and nutrients removal. P recovery strategy based on P mass balance of the process was employed where sludge retention time (SRT) of the systems was extended. Meanwhile, the anoxic/aerobic volume ratio was increased to enhance the activity of denitrifying P uptake. The results show that up to 59.8% and 75.2% of P from real and synthetic wastewaters were continuously recovered at the SRT of 35 d, respectively. The lower P recovery efficiency of the system fed with real wastewater was due to its lower influent P load and P content in activated sludge after P recovery was decreased from 0.059 mgP/mgVSS to 0.033 mgP/mgVSS. The analysis of the kinetic and stoichiometric parameters suggested that activities of the polyphosphate accumulating organisms (PAOs) in P recovery systems were retained under high P recovery efficiency, and more glycogen was degraded to provide energy for acetate uptake. This resulted in the highest average TP removal efficiency of 94.0% for the AAO-SBSPR process fed with real wastewater. Moreover, the enhancement of denitrifying P uptake activity was observed in P recovery systems. It was further improved by increasing the volume of the anoxic tank, which resulted in better TN removal performance. Meanwhile, the diversity of the microbial community was increased as the system was changed from the AAO process to the AAO-SBSPR process, and the relative abundances of the key functional bacteria such as nitrifiers, denitrifiers, PAOs and DPAOs were increased which strengthened the N-related metabolic pathways of the system remarkably.

Novel approach to improving wastewater treatment and sewage sludge combustion using pulverized coal-activated sludge.

Sewage and sludge are usually treated separately. Considering improving sludge treatment while improving sewage treatment is beneficial to the synergetic effect of sewage treatment and sludge treatment. The efficiency of pulverized coal-activated sludge (PAS) on contaminant removal, sludge calorific value, and combustion characteristic was investigated in contrast to conventional activated sludge (CAS) using the laboratory-scale sequencing batch reactor (SBR). Results indicated that the average chemical oxygen demand, ammonium nitrogen, total nitrogen, and total phosphorus removal efficiency of PAS were highest under a dosage of 0.4g/L, which were 98.56%, 94.22%, 68.60%, and 95.96%, respectively. The average effluent concentration satisfied the Level A discharge standard of pollutants for municipal wastewater treatment plants (GB18918-2002). The calorific value and maximum weight loss of PAS gradually increased adjusting the dosage of pulverized coal. At the pulverized coal dosage of 0.2g/L, the calorific value of PAS with 70% water content is 3,824.07kJ/kg, which can satisfy the requirement of self-maintained combustion. Overall, the pulverized coal can simultaneously improve the treatment of wastewater in SBR and promote the sludge combustion by increasing calorific value. Therefore, PAS system is an innovation based on improving the sewage treatment sludge combustion. PRACTITIONER POINTS: An innovative method to simultaneously improving wastewater treatment and sewage sludge combustion using pulverized coal-activated sludge was developed. The average COD, , TN, and TP removal efficiency of PAS-0.4 is best. The 70% moisture content sludge calorific values of 3,824.07kJ/kg in PAS-0.2 can satisfy the requirement of self-maintained combustion.

Characteristics of Nutrient Removal in a Pilot-scale A2/O with Mixture of Sludge Fermentation Liquor and Tail Water as External Carbon Source

To resolve the issue of sewage fluctuation and discontinuity in a rural district of China, a new operation mode of replenishing the mixture of fermentation liquor and tail water during the off-flow period was proposed, and the nutrient removal performance of a pilot-scale A2/O system with this operation mode was investigated. The results of beaker experiments found that the mixture of tail water and fermentation liquor at a ratio of 12:1 had better denitrification and phosphorus release/absorption characteristics than the raw water, and theoretically had the function of enhancing denitrification and phosphorus removal performances. The results of a 97 d pilot test showed that the removal efficiency of TN and TP was improved after the system was adjusted from the constant flow mode to this new operation mode, and the average removal rate of TN and TP increased from 69.27% and 86.94% to 73.34% and 89.94%, respectively. The corresponding average effluent concentration decreased from 15.77 mg·L-1 and 0.80 mg·L-1 to 13.76 mg·L-1 and 0.64 mg·L-1. The sequencing results of the 16S rRNA gene showed that this new operation mode was beneficial to the enrichment of five common hydrolytic acidizing bacteria genera, six phosphorus-accumulating organisms genera, and four denitrifying bacteria genera. This was also the main reason for the improved nutrient removal performance. According to the long-term monitoring of the characteristics of activated sludge, this new operating mode will degrade the sedimentation performance of activated sludge in the system, and the average SVI increased from 106 mL·g-1 to 131 mL·g-1. However, this degree of deterioration did not adversely affect the sludge activity and nutrients removal performance of the system, and there was no sludge bulking in the entire experiment. The results of this study have shown that the A2/O system can maintain and improve the performance of nutrients removal by replenishing the mixture of tail water and sludge fermentation liquor when the flow is cut off. This will provide new ideas for the design and operation of sewage treatment plants in rural areas in the future.

Treatment of high-strength sewage by textile fibers-based sequencing batch biofilm reactor for simultaneous removal of organics and nutrients

This study investigates the effectiveness of SBBR with low-cost textile fibers-based bio-carrier namely polypropylene fibers for the treatment of real sewage. The influent loading rates of COD, TN, and TP were averaged at 0.2780, 0.0170, and 0.0077 kg/m3.d, respectively. The removal efficiencies of BOD, COD, TN, and TP recorded in SBBR were 98%, 93%, 82%, and 44%, respectively at an aeration time of 4 h. The TN and TP removal achieved in SBBR were 2.05 and 2.75 times, respectively higher than SBR. The COD removal efficiency was more than 90% under all SRT conditions (10, 14, 18, 22, and 26 d) in SBBR, and the highest efficiency of 93% was obtained at an SRT of 22 days. As the SRT increased, the nitrogen and phosphorus removal decreased, because the denitrification rate and phosphorus release and uptake rate decreased at longer SRT. Simultaneous nitrification and denitrification (SND) efficiency was 85% in SBBR and 44% in SBR, indicating the co-existence of aerobic nitrifiers and anoxic denitrifiers in the biofilm reactor. In SBBR, the nitrogen mass balance showed 74% of nitrogen removed by denitrification, 9% was removed through sludge wasting process, and 13% was removed in effluent at an SRT of 22 days and DO concentration of 3 mg/L. The t-test results suggest that the performance of SBBR was better than SBR in nitrogen and phosphorus removal at a 95% confidence interval.

Performance of novel constructed wetlands for treating solar septic tank effluent

To improve treatment performance of the solar septic tank technology, novel constructed wetland systems have been proposed as an effective post-treatment system. This study aimed to investigate the treatment performance of the multi-soil layer based constructed wetland (MSL-CW) and comparing with the modified constructed wetland (mCW) for treating solar septic tank effluent in long-term operation. Pilot-scale MSL-CW and mCW units were operated in parallel under the same conditions during the period of 2016–2019. Removal efficiencies of TCOD, SCOD and TBOD in the MSL-CW were not significantly different (p < 0.05) from those of the mCW unit, which were 70–72%, 63–68% and 78–82%, respectively. The removal efficiencies of TSS, TKN, NH4-N and TP were found in the same magnitude in both units. The total coliform and E.coli counts in the effluent of MSL-CW and mCW units were reduced from 105 MPN/100 mL to be lower than 103 MPN/100 mL. These long-term operational results demonstrated that the effluent from the MSL-CW and mCW units could meet the global standards of non-sewered sanitation systems and the WHO guidelines. The effects of seasonal variations and plant harvesting on the monthly treatment performance are discussed in this study.

Treatment of microcystin (MC-LR) and nutrients in eutrophic water by constructed wetlands: Performance and microbial community

Cyanobacterial harmful algal blooms and microcystins (MCs) pollution pose serious threat to aquatic ecosystem and public health. Planted and unplanted constructed wetlands (CWs) filled with four substrates (i.e., gravel (G-CWs), ceramsite (C-CWs), iron-carbon (I-CWs) and slag (S-CWs)) were established to evaluate nutrients and a typical MCs variant (i.e., MC-LR) removal efficiency from eutrophic water affected by the presence of plant and different substrate. The response of the microbial community to the above factors was also analyzed in this study. The results indicate that the presence of plant can generally enhance nutrients and MC-LR removal efficiency in CWs, except for I-CWs. Throughout the experiment, all CWs exhibited good nitrogen removal efficiency with removal percentages exceeding 90%; TP and MC-LR average removal efficiency of C-CWs and I-CWs were greater than G-CWs and S-CWs irrespective of the presence of plant. The best MC-LR removal efficiency under different MC-LR loads was observed in planted C-CWs (ranged from 91.56% to 95.16%). Except for I-CWs, the presence of plant can enhance relative abundances of functional microorganisms involved in nutrients removal (e.g., Comamonadaceae and Planctomycetaceae) and MCs degradation (e.g., Burkholderiaceae). The microbial community diversity of I-CWs was simplified, while the relative abundance of Proteobacteria was highest in this study. The highest relative abundances of Comamonadaceae, Planctomycetaceae and Burkholderiaceae were observed in planted C-CWs. Overall, ceramisite and iron-carbon were more suitable to be applied in CWs for nutrients and MC-LR removal. This study provides a theoretical basis for practical application of CWs in eutrophication and MCs pollution control.

Achieving simultaneous biological nutrient removal and sludge minimization from marine ship sewage based on an innovative Landscape Integrated Ecological Treatment System (LIETS)

The implementation of latest emission standards of International Maritime Organization (IMO) has raised more stringent dicharge limitations for marine domestic ship sewage. Hence, availability of highly-efficient, eco-friendly and profitable ship-generated sewage biological strategy is necessary. In this study, an innovative landscape integrated ecological treatment system (LIETS) based on modified denitrifying phosphorus removal (mDPR) process for sustaining marine ship sewage treatment was investigated. Over 200 days experimental results revealed that the satisfactory TN, TP and COD removal efficiencies of 82.0%, 81.0% and 94.0% were achieved, leading to the effluent concentration were 10.9 mg·L−1, 0.97 mg·L−1 and 17.8 mg·L−1, respectively. The mean nutrient removal efficiency maintained above 90.0% despite 1.5–2.0 times influent organic loading rate (OLR) shock, along with the SS and BOD5 achieving less than 20.0 mg·L−1 and 17.0 mg·L−1, while polysaccharide (PS)/protein (PN) ratio reached the valley value causing the excellent sludge flocculation and sedimentation during anaerobic period. Promoting aeration rate rather than NOx−-N recirculation was demonstrated as an efficient strategy for minimizing the inhibitory effect of excess organic shock. Furthermore, Aeromonas (42.31%) belonging to γ-Proteobacteria was identified as critical denitrifying phosphorus accumulating organisms (DPAOs) responsible for the desirable performance. The mixture mode of excess sludge and feed played significant roles in sludge reduction, and LIETS was proved to be a promising opportunity for marine ship sewage treatment application.

Study of pyrite based autotrophic denitrification system for low-carbon source stormwater treatment

Improving the nitrogen removal capacity of stormwater runoff has been the main research direction of bioretention systems in recent years. Heterotrophic denitrification in traditional bioretention systems was often used, but insufficient carbon sources in the runoff limit it. In this study, two bioretention systems using natural pyrite and zeolite as substrates were constructed to explore the feasibility of pyrite-based autotrophic denitrification in bioretention for nitrogen removal. During eight months of operation at natural conditions, the results showed that pyrite had no negative effects on the removal of NH4+—N, but enhanced denitrification in the bioretention system with no or low carbon source in the influent. Pyrite based bioretention system (PBS) can adapt to low temperature and irregular wet and dry alternation. The average NH4+—N, TN, and TP removal efficiency of PBS during eight months were 87.6 %, 89.3 %, and 81.6 %. The average NH4+—N, TN, and TP removal efficiency of zeolite-based bioretention system (ZBS) were 98.7 %, 47.1 %, and 47.5 %. By-products (SO42- and Total iron) of PBS were all at an acceptable level. The dominant genera in PBS were Denitratisoma (3.6 %), Ellin6067 (2.7 %), Thiobacillus (2.6 %), Thauera (2.1 %), CL500−29 marine group (1.8 %), Sulfuritalea (1.7 %), Subgroup 10 (1.4 %). Genera Thiobacillus, Thauera, and Sulfuritalea were highly related to autotrophic denitrification. Moreover, genera Denitratisoma was highly related to heterotrophic denitrification. This study shows that pyrite could be a promising eco-friendly substrate in the bioretention system for nutrient removal.

Formation and characteristics of filamentous granular sludge.

Aerobic granular sludge process as a promising biotechnology has been one of the research hotspots in the area of wastewater treatment during the last two decades. In our study, after around 60 days' operation, filamentous granular sludge (FGS) was formed under low aeration (SAV = 0.085 cm/s) and multi-feeding conditions. The characteristics of FGS and the performance of the FGS system for organic matter and nutrients removal were investigated. The results showed that chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies were relatively stable, while COD removal efficiency increased from 82% to 94% in the presence of sulfamethoxazole (SMZ) at low concentration (1 mg/L). At the same time, the TP removal efficiency could be improved and maintained at around 75%, while TN removal efficiency was flocculated at around 50%. The analysis of microbial diversity showed that Thiothrix and Trichococcus as typical filamentous species were detected and dominant in the FGS system. The abundance of Thiothrix increased from 15% to 34%, while Trichococcus decreased from 23% to 3% in the presence of SMZ.

Nutrient removal, methane and nitrous oxide emissions in a hybrid constructed wetland treating anaerobic digestate

A pilot hybrid constructed wetland (CW) planted with reeds (Phragmite australis) and rice (Oryza sativa L.) was designed to treat liquid anaerobic digestate in the Yangtze River Delta, China. The hybrid CW system was composed of four stages: two reed vegetated vertical subsurface flow beds (VSSF: U1 and U2) in sequence, followed by a reed vegetated horizontal subsurface flow bed (HSSF: U3) and a rice vegetated surface flow bed (SF: U4). The average loading rate of digestate was 3.6 m3 per day during the experimental period.The average concentrations of TN and TP in the influent were 379 ± 58 mg L−1 and 29.6 ± 9.2 mg L−1, while the average removal efficiencies of TN and TP were 94.6% and 88.4%. Both TN and TP removal efficiencies in the second VSSF containing zeolite gave the highest removal performance, in which the mass removal rates were 21.3 ± 8.0 g-N m−2 d−1 and 0.99 ± 0.69 g-P m−2 d−1, respectively. Similarly, the highest removal performance for COD was also observed in the second VSSF with a mass removal rate of 79.9 ± 72.4 g-COD m−2 d−1.On the other hand, the average CH4 and N2O fluxes were highest in the first VSSF, at 31.8 ± 12.9 mg m−2 h−1 and 3.7 ± 2.8 mg m−2 h−1, respectively. There was a significant linear relationship between CH4 flux and DOC concentration in the pore water as well as a correlation between N2O flux and TN concentration. Total GWP of the hybrid CWs, derived from CH4 and N2O emissions, was 792.4 kg CO2-eq, of which CH4 and N2O emissions accounted for 66.0% and 34.0%, respectively. Consequently, the hybrid CWs emitted on average 0.93 kg CO2-eq to remove 1 kg COD while the average EF of TNin was 0.34%, suggesting that the use of multistage hybrid CWs could be efficiency-wise and environmentally a promising strategy for anaerobic digestate treatment.