COD Loading Research Articles

Urban wastewater treatment at ambient conditions using microalgae-bacteria consortia in a membrane high-rate algal pond (MHRAP): The effect of hydraulic retention time and influent strength

The effects of hydraulic retention time (HRT) and influent wastewater strength on microalgae-bacteria performance were studied in two sets of experiments in a 6-day biomass retention time membrane high-rate algal pond (MHRAP) pilot plant to assess its pollutants removal potential. In the first set of experiments, the MHRAP was continuously fed with effluent from primary settling and operated at 6-, 4- and 2-days HRT and in the second set, the MHRAP was operated at 4-, 2-, and 1-day HRT using pre-treatment effluent. Results showed a complex interaction between algae-bacteria consortium, ambient conditions and MHRAP operation. In set 1, the highest total nitrogen (T-N) and total phosphorus (T-P) removal efficiencies were reached with 6-day HRT (23.6±0.6 % and 32±4 %, respectively), partially due to free ammonia nitrogen stripping and phosphorus precipitation, because of abiotic factors, which reduces the activity of nitrite-oxidizing bacteria and led to partial-nitrification. On the other hand, the 4 and 2-day HRT T-N and T-P removal efficiencies were reduced (below 10 % and 5 %, respectively) because the abiotic factors limited the physicochemical processes, and less biomass was taken up. In set 2, a suitable equilibrium between the microalgae and bacterial communities at 2-days HRT achieved high T-N (91±5 %) and T-P (71±8 %) removal efficiencies. Mass balances indicated that the nitrogen was mostly removed by nitrification-denitrification (87 % of T-N) and T-P predominant removal mechanism was precipitation. The COD removal efficiencies were higher than 86 % in both sets, since the particulate COD and colloids were removed by ultrafiltration. The obtained results showed that MHRAP technology would allow reducing COD and nutrient loads in the effluent under certain operating conditions, demonstrating the potential for resource recovery and wastewater treatment of microalgae-bacteria consortia.

Spatio-temporal characteristics and multi-scale risk identification of pollution load based on sensitivity analysis in small watersheds located in Tuojiang River Basin, China.

High-quality development of water resources supports high-quality socio-economic development. High-quality development connects high-quality life, and clarifying the key management contents of small watersheds plays an important role in building ecologically clean small watersheds and promoting regional production and life. Previous research on pollution loads has focused on examining the impact of various external drivers on pollution loads but still lacks research on the impact of changes in pollution sources themselves on pollution loads. In this study, sensitivity analysis was used to determine the impact of changes from different sources on the total pollution loads, which can recognize the critical pollution sources. We first employed the pollutant discharge coefficient method to quantify non-point source pollution loads in the small watershed in the upstream Tuojiang River basin from 2010 to 2021. Then, combination sensitivity analysis with Getis-Ord Gi* was used to identify the critical sources and their crucial areas at the global, districts (counties), and towns (streets) scales, respectively. The results indicate: (1) The pollution loads of COD, NH3-N, TN, and TP all show a decreasing trend, reducing by 18.3%, 16.2%, 18.6%, and 28.1% from 2010 to 2021, respectively; (2) Livestock and poultry breeding pollution source is the most critical source for majority areas across watershed; (3) High-risk areas are mainly concentrated in Jingyang district and its subordinate towns (streets). There is a trend of low-pollution risk areas transitioning to high-pollution risk areas, with high-risk areas predominantly concentrated in the southeast and exhibiting a noticeable phenomenon of pollution load spilling around. This study can promote other similar small watersheds, holding significant importance for non-point source pollution control in small watersheds.

Biophysics indicators as the sustainable strategy for river pollution control (case study in Jangkok River, Mataram City, West Nusa Tenggara)

Background: Sungai Jangkok is one of those considered heavily polluted in NTB. The Biochemical Oxygen Demand (BOD) value has exceeded the standard for Class II water quality, and according to the Family Biotic Index (FBI) value, the river falls under the category of heavy organic pollution. The research objective is to realize sustainable management of the Jangkok Watershed in accordance with its river functions by implementing pollution control strategies. Methods: Data collection was conducted using questionnaires and interviews with the public and stakeholders (government and NGOs). Water quality data was obtained from DLHK NTB and DLH Mataram City, and sampling was carried out using the composite sample technique. The methods employed were STORET, QUAL2Kw, logistic regression, and SWOT. Findings: The research findings indicate that, in general, the Jangkok River in Mataram City falls into the heavily polluted category from 2015 to 2022, with an average STORET score of -79.25. Moreover, the pollution loads of BOD, COD, and TSS entering the river have exceeded the pollution carrying capacity. The condition is influenced by several factors, including the less favorable perception of pollution status (67%) and the usefulness of the river (59%) by the community. Additionally, the persistent behavior of littering and/or defecating in the river (23%), inadequate preventive practices (59%), insufficient wastewater disposal facilities (40%), and improper waste management (58%) are contributing factors. Moreover, the existence of houses backing up to the river (59%) also plays a role in the current condition. Some of the causes are the lack of synergy across administrative regions between stakeholders, the absence of law enforcement for the community, dependency on government budget for work programs, and the lack of incentives. Conclusion: The conclusion of this research suggests that the most effective strategy for taking is to develop a program for reducing pollutant loads that is integrated across districts and cities, integrated across agencies with various levels of authority, integrated with the community, and in accordance with the river's actual conditions and the socioeconomic community. Novelty/Originality of this Study: This study provides a novel approach by integrating quantitative water quality modeling (QUAL2Kw) with community behavior analysis to develop a sustainable and comprehensive strategy for controlling river pollution in the Jangkok watershed, Mataram City.

Effect of lactose as a co-substrate in the biodegradation of an anionic surfactant “LAS” by anaerobic digestion

Sodium alkylbenzenesulfonate (LAS) is the most widely used anionic surfactant in the manufacture of commercial detergents due to its excellent detergent properties and low cost. However, they are highly polluting products due to their chemical composition, causing a serious problem of pollution and eutrophication in natural bodies of water, if the amount dumped and the frequency with which they are dumped is taken into account. In addition, damage to health and ecosystems by remaining in the environment for a long time, is a relevant issue of immediate attention. This article presents the results found when using lactose as a co-substrate on the simultaneous biodegradation of the LAS surfactant in an arrangement of UASB-type anaerobic reactors in two stages; with a hydraulic retention time of 0.25 days in the acidogenic reactor in which two surfactant concentration rates were evaluated: 200 ± 0.49 mg/L with an organic load of 5.92 ± 0.5 KgCOD/m3.d (experiments II, III and V) and 300 ± 0.05 mg/L with organic loading. of 6.8 ± 0.11 KgCOD/m3.d (experiment VI) and of one day, in the methanogenic reactor. The results showed that the acidogenic reactor was able to eliminate COD by 42.24% and biodegrade LAS by 86.65% (experiment V). At 300 mg/L (experiment VI), these values are reduced to 36.6 and 55% respectively. For its part, the methanogenic reactor fed with the effluent of the acidogenic reactor (experiment V) with a lower concentration of COD, LAS and organic load, showed a COD removal and LAS biodegradation efficiency of 83.17 and 13.85% respectively.

Separation of Cellulose from Wastewater and Valorisation via Pyrolysis: A Case Study in the Czech Republic

Currently, the recovery of resources from urban wastewater (WW) represents a priority. On this topic, the potential recovery of cellulose for its subsequent reuse in different sectors is gaining interest. In this work, a large-size conventional wastewater treatment plant (WWTP) was selected as a case study. A preliminary mechanical treatment was used, with the aim of separating, quantifying, and characterizing cellulose in WW. The results suggest that the per-capita production of dry primary cellulosic sludge (D-PCS) is equal to 1.46 ± 0.13 kgD-PCS PE−1 y−1, with an average calorific value of 21.04 MJ kg−1DM. Cellulosic fibres have an average length of >100 µm and a thickness of 2–5 µm. The D-PCS was subsequently treated via medium-temperature pyrolysis; a total of 29.5% of the initial D-PCS was converted into pyrolyzed primary cellulosic sludge (P-PCS) and only 26% into pyrolytic gas. More than 44.5% of the dried cellulose can be converted into pyrolytic oil. Moreover, three different scenarios of recovery have been considered, and the impact of cellulose separation in terms of COD fluxes entering the WWTP and potential energy recovery has been studied. The results suggested that, in this case study, the potential separation of the primary cellulosic sludge from the influent water flux would have no significant impact on COD load entering the biological treatments and biogas production in the anaerobic digestion of the secondary sludge.

Deciphering the photoelectrochemical behaviour of MoSe2-decorated BiVO4 as a dual system for concurrent degradation of methylene blue and hydrogen generation

Green hydrogen production through photoelectrochemical (PEC) water splitting offers a sustainable energy solution, but the utilization of low-quality water is essential to conserve freshwater resources. Repurposing industrial wastewater, a substantial global issue, for PEC water splitting remains underexplored due to challenges in photoelectrode efficiency and stability. In this study, we present a MoSe2-decorated BiVO4 heterostructured photoelectrode (MoSe2/BiVO4 or BM) for green hydrogen production and efficient wastewater treatment. The optimized system yields a hydrogen production rate of 0.113 mmol from synthetic textile water (utilizing methylene blue as a model pollutant) while achieving a 94.74% degradation of pollutants. Synthesized via a hydrothermal route, BM demonstrates a high photocurrent density of 2.57 mA/cm2 at 1.23 V vs RHE, surpassing BV alone (0.14 mA/cm2). Further, BM shows incident photon to current efficiency (IPCE) of 12.24% and applied bias to photocurrent efficiency (ABPE) of 0.59%. Scavenger studies elucidate the role of holes in MB degradation. Tested in textile wastewater treatment outlets, BM exhibits a hydrogen production rate of 6.155 μmoles alongside reduced COD, BOD, TOC, and microbial load, showcasing its dual capability for hydrogen generation and simultaneous wastewater treatment. Thus, the efficiently designed type-II heterostructure formed between BV and MS behaves as a dual system with demonstrated usage in low-quality water for hydrogen generation with its simultaneous treatment.

Innovative approach for predicting biogas production from large-scale anaerobic digester using long-short term memory (LSTM) coupled with genetic algorithm (GA)

An artificial neural network (ANN) model called long-short term memory (LSTM), coupled with a genetic algorithm (GA) for feature selection, was used to predict biogas production of large-scale anaerobic digesters (ADs) of Tehran South Wastewater Treatment Plant (Iran), with a biogas production of approximately 30,000 Nm3/d. In order to employ the real conditions, the hydraulic retention time (HRT) of the ADs (21 days) was considered as the LSTM look-back window. To evaluate the model predictions, three different scenarios were defined. In the first scenario, the model predicted the produced biogas by using raw wastewater characteristics and reached the coefficient of determination of R2 = 0.84. The GA selected four out of eleven parameters of raw wastewater, including loads of BOD5, COD, TSS, and TN (kg/d), as the most informative data for the model. In the second scenario, the model predicted the produced biogas by employing the data of the thickened sludge streams entering the ADs and yielded a higher accuracy (R2 = 0.89). In this scenario, GA selected two out of six parameters of the sludge streams, including total flow rate (m3/d) and average solids content (w/w%). Finally, in the third scenario, by putting the parameters of the two previous scenarios together, the model's prediction accuracy increased slightly (R2 = 0.90). The results demonstrated that the GA-LSTM modeling technique could achieve reliable performance in predicting biogas production of large-scale ADs by including HRT in modeling procedure. It was also found that the raw wastewater characteristics severely affect AD behavior and can be successfully used as the input data of the AD models.

The Use of Fly Ash and Bottom Ash to Reduce COD, TSS, and Color in Textile Industry Wastewater Effluent

The textile industry wastewater effluent contains some levels of COD, TSS, and color, it must be reprocessed as a tertiary treatment using the filtration method. The goal of this research was to examine the ability of fly ash and bottom ash as filtration media to reduce the pollutant / organic load of COD, TSS, and color in textile industry wastewater effluent. The slow sand filter method was used in this study, and the filter media was derived from coal combustion waste. The variation used in this study is a variation of filter media (fly ash and bottom ash), with fly ash diameters of 0.11 and 0.35 mm, bottom ash diameters of 0.85 - 1.50 mm, and media thickness of 1.50 - 2.00 mm (10 cm and 20 cm). The study’s findings demonstrated that using bottom ash and fly ash media in the filtration process with a slow sand filter system could maximize the efficiency of reducing COD, TSS, and color levels in textile industry wastewater effluent. In fly ash media, it can reduce COD, TSS, and Color by 90.58%, 81.87%, and 100%. Meanwhile, Bottom Ash filter media has an average COD, TSS, and Color reduction of 87.80%, 81.87%, and of 100%.

Water quality management by enhancing assimilation capacity with flow augmentation: a case study for the Yamuna River, Delhi.

This paper aims to assess the requirement of load reductions and flow augmentation to enhance the assimilation yield of the Yamuna River, Delhi. The framework QUAL2kw was used to predict river quality. The model was calibrated and confirmed in critical flow conditions of pre-monsoon periods. Three strategies were established for varying pollutant loads. The DO concentration was predicted with changing BOD and COD loads. The 16 outfalling drains were considered pollutant sources between the 22 km stretch of the river. Four cases with 41 scenarios were studied with varying flow augmentation upstream and varying load. It has been observed that with 80 cumecs of upstream flow, the reach can assimilate 31.33 tonnes per day of BOD and 142.85 tonnes per day of COD load, maintaining the desired level of DO (≥4 mg/L) and BOD (≤3 mg/L) throughout the reach.

Machine learning model optimization for removal of steroid hormones from wastewater

In the past few decades, there has been a significant focus on detecting steroid hormones in aquatic environments due to their influence on the endocrine system. Most compounds of these pollutants are the natural steroidal estrogens, i.e., estrone (E1), 17β-Estradiol (E2), and the synthetic estrogen 17α-Ethinylestradiol (EE2). The Moving-Bed Biofilm Reactor (MBBR) technique is appropriate for eliminating steroid hormones. This study centers on creating a model to estimate the effectiveness of the MBBR system regarding its ability to eliminate E1, E2, and EE2. The results were modeled with artificial neural networks (ANNs). The Particle Warm Optimization (PSO) and Levenberg Marquardt (LM) algorithms were selected for network training. The models incorporated five input parameters, encompassing the COD loading rate, initial levels of E1, E2, and EE2 steroid hormones, and Hydraulic Retention Time (HRT). The optimum removal conditions (three steroid hormones and COD) were determined using the optimized ANN based on both PSO and LM algorithms. The optimal transfer functions for the hidden and output layers were identified as tan-sigmoid and linear, respectively. The best ANN structures (Neurons in input, hidden, and output layers) and correlation coefficients (R) were 5:9:4, with R = 0.9978, and 5:10:4, with R = 0.9982 for the trained networks with LM and PSO algorithms, respectively. Eventually, the input parameters' importance was ranked using sensitivity analysis (SA) through Pearson correlation and developed ANNs.

Enhanced nitrogen removal performance of microorganisms to low C/N ratio black-odorous water by coupling with iron-carbon micro-electrolysis

Black-odorous water was caused by urbanization, industrial sewage and domestic sewage. Black-odorous water with low carbon nitrogen ratio (C/N) may inhibit the activity of microorganisms due to the lack of C source during microbial treatment. In this study, iron-carbon micro-electrolysis (ICME) was used to couple nitrifying and denitrifying bacteria. The external factors affecting microbial activity were optimized through experiments, and the effect of low C/N wastewater was studied. The optimal external factors were temperature of 30 ℃, C/N of 3, DO of 3 mg/L and iron-carbon dosage of 150 g/L. Coupled with ICME, it was found that the removal rate of nitrate nitrogen in water increased by 50.74 %, indicating that ICME could make up for the deficiency of microbial C source and improve the removal rate of nitrate nitrogen in low C/N black-odorous water. The improvement of removal rate had much to do with ICME's role as electron donor to provide electrons for denitrification. In addition, the performance of wastewater treatment by this process is tested. The maximum load of ammonia nitrogen, COD, nitrate and total nitrogen was increased to 0.1928, 1.7732, 0.2691 and 0.5181 kg/(m3·d), respectively. High-throughput sequencing results showed that the species of dominant plant population changed after ICME coupling, but the abundance increased significantly, which further indicated that ICME played a synergic role in microbial nitrogen removal, which was related to the release of trace iron by ICME. This study can provide some guidance for the treatment of black-odorous water with high ammonia nitrogen and low C/N.

Penyisihan COD, TSS, dan TN pada Lindi TPA Klotok Menggunakan Anoxic-Oxic Moving Bed Biofilm Reactor

Leachate is a liquid containing extracted, dissolved, and suspended materials from waste in a landfill. Leachate from Klotok landfill contains pollutant loads that do not meet the water quality standards, necessitating treatment. In this study, parameters considered were COD, TSS, and TN. Anoxic-Oxic Moving Bed Biofilm Reactor (MBBR) was chosen due to its compact footprint, low sludge production, ability to handle high COD loads, and not requiring periodic backwash. Variations including media type, media volume, and Hydraulic Retention Time (HRT) were applied to reduce pollutant parameter concentrations. The experiment was conducted in batch-continuous mode. The derived parameter concentrations yielded promising results using a biocube/sponge media in the reactor, constituting 50% of the leachate volume, with an HRT of 45 hours. Upon continuous operation under the best variations for parameter reduction, COD, TSS, and TN values were achieved as 160 mg⁄L, 132 mg⁄L, and 31.5 mg⁄L, respectively. Meanwhile, the average removal percentages for COD, TSS, and TN were 87%, 50%, and 87% respectively. Additionally, microorganism identification was performed in the anoxic-oxic moving bed biofilm reactor, revealing the presence of microorganisms such as coliforms, Bacillus sp., and Pseudomonas sp.

Performance evaluation and optimization of simultaneous phosphorus and nitrogen removal from anaerobically digested liquid-dairy-manure using an intermittently-aerated-extended-idle sequencing batch reactor

Wastewater from confined dairy operations requires efficient treatment to reduce its potential to pollute the surrounding environments. In this study, a novel intermittently-aerated-extended-idle sequencing batch reactor (IA-EI SBR) process was developed, evaluated, and optimized for simultaneously removing phosphorus (P) and nitrogen (N) from anaerobically digested liquid-dairy-manure (ADLDM) with lower carbon-to-nutrient-ratios. Four influential operating parameters including cycle-time of 5–9 h, intermittent-aeration strategy of 10–50 min/h, two feed-phases of 6–30 min, and idle-phase of 40–120 min were statistically analyzed using central-composite design coupled with response-surface methodology for optimal removal efficiencies of ortho-phosphorus (%OPremoval), total-phosphorus (%TPremoval), ammonia-nitrogen (%NH3-Nremoval), total-nitrogen (%TNremoval), and chemical oxygen demand (%CODremoval). Results showed that the interactions of cycle time-idle phase, and aeration strategy-feed phases were significant in affecting %TPremoval (p-value ≤ 0.005). The synergistic effect of aeration strategy-idle phase was significant for %TNremoval and %CODremoval (p-value ≤ 0.006), while the cycle time-feed phases interaction had significant effect on %NH3-Nremoval. The maximum simultaneous nitrification-denitrification (SND) efficiency of 85.7% was recorded under influent COD and TN loading of 3,999.2 and 785.7 mg L−1 at 30 min/h aeration time in 7 h. The quadratic regression models based on statistical analysis of the experimental results adequately described the IA-EI SBR performance and showed that the applied levels of operating parameters were highly correlated with all five responses (p-value ≤ 0.030). Operating conditions for optimal IA-EI SBR process efficiency determined by desirability analysis were cycle-time of 8 h, intermittent-aeration strategy of 36 min/h, feed-phases of 24 min, and idle-phase of 100 min. Under these optimal conditions, the corresponding removal efficiencies for OP, TP, NH3-N, TN, and COD of 82.64, 95.82, 92.92, 73.84, and 90.94%, respectively, were achieved in validation experiments.

A series anaerobic-aerobic down-flow hanging sponge (DHS) reactor for the treatment of palm oil mill effluent (POME)

Palm oil mill effluent (POME) contains very high organic compounds that must be treated before being discharged into the environment. Pond technology has been widely used for the treatment of POME; however, it requires a huge area of land. Down-flow hanging sponge (DHS) reactor has shown a high pollutant removal efficiency, less energy, and land area requirement. This study aimed to investigate the performance of a series of anaerobic (R3) and aerobic (R4) DHS reactors in treating POME. The reactor was continuously supplied with POME in three different phases for 165 days. The COD loading rate was set at 3.06, 6.12, and 12.24 kg-COD/m³·day in Phase 1, Phase 2, and Phase 3, respectively. Hydraulic retention time (HRT) was set at 47 min and 50 min, in R3 and R4, respectively. The reactors showed good performance for pollutant removal efficiency, especially COD. In Phase 1, the average COD removal rate was 2.68 and 0.27 kg-COD/m³·d in R3 and R4, respectively. In Phase 2, when the COD loading rate was increased, the average COD removal rate achieved 4.12 and 1.53 kg-COD/m³·d in R3 and R4, respectively. In Phase 3, the COD loading rate was doubled to 12.24 kg-COD/m³·day and the average COD removal rate of 5.81 and 2.90 kg-COD/m³·d was achieved in R3 and R4, respectively. During operation, the concentration of nitrate fluctuated in R4, which indicated that nitrification had occurred. Phosphate could be reduced in R3, but only a small portion could be removed in R4. Total suspended solids (TSS) could be effectively removed in R4. These results revealed that a combination of anaerobic-aerobic DHS reactors showed good performance in removing pollutants such as COD and TSS. Therefore, DHS technology can be used as a polishing treatment for treated POME.

Palm oil mill effluent (POME) treatment using a combined anaerobic-microalgae down-flow hanging sponge (DHS) reactor

Palm oil mill effluent (POME) generated from the production of palm oil contains organic and inorganic contaminants that can be a nutrient source for microorganisms such as bacteria, fungi, and microalgae. In this study, POME was treated using a combined anaerobic (R1) and microalgae (R2) in down-flow hanging sponge (DHS) reactor. Chlorella pyrenoidosa was immobilized in sponge carriers of R2 and LED lights were used for 12 hours per day to support microalgae growth. The DHS reactors were continuously operated for 165 days in three phases with different COD loading rates, namely 3, 6, and 12 kg-COD/m³·day in Phase 1, Phase 2, and Phase 3, respectively. The hydraulic retention time (HRT) was set at 46 min and 52 min in R1 and R2, respectively. The highest COD removal rate was achieved at 6.93 kg-COD/m³·day and 4.85 kg-COD/m³·day in R1 and R2, respectively. In addition, maximum phosphate removal was 68% in both reactors. Increased concentration of nitrate in R-2 indicated that nitrification may occur in the reactor. The pH of R1 effluent was relatively stable at neutral conditions, while the pH value of R2 effluent slightly increased. Based on visual observation, bacteria biofilm also grew in the microalgae reactor (R2). Synergistic bacteria-microalgae may play an important role in pollutant removal. The results of this study show that a combined anaerobic and microalgae DHS reactor can be used as an alternative for POME treatment because they have a shorter HRT and can be applied in a small area.

Pollutant removal modeling in a hybrid wetland system for industrial wastewater treatment

Modeling of treatment wetlands allows the prediction of system behavior and facilitates large-scale design by evaluating the effects of modifying the operating parameters. The aim of this study was to calibrate and verify applicable models in vertical flow (VF) and horizontal subsurface flow (HSSF) wetlands -first and second stage of the hybrid wetland (HW) system- operating in site-specific environmental conditions. Stepwise multiple linear regression analysis, oxygen demand model, and k-C* model, were applied to each stage of the HW system as appropriate. All models were calibrated and verified based on the data observed by monitoring the HW system. Afterwards, simulations were performed at each stage of the HW system. The simulations show the dependence of nitrification on the availability of NH4+-N and also that both, the increase in Org-N and COD loading, affect the efficiency of nitrification in the VF stage. In the HSSF stage, simulations show that the increase in hydraulic or pollutants loading rate has a positive impact on the performance of the system. The fit achieved in the models was satisfactory and the results obtained by simulation provide a useful tool to evaluate the performance of the HW system in different possible operating scenarios.

Effect of High Hydrostatic Pressure Processing on the Microbiological Quality and Bacterial Diversity of Sous-Vide-Cooked Cod

High hydrostatic pressure (HP) is a promising method to improve the microbiological quality of sous-vide foods. Monitoring the composition and behavior of the microbial communities in foods is of most importance for the production of high-quality and safe products. High-throughput sequencing (HTS) provides advanced approaches to determine food's microbial community composition and structure. The aim of the present study was to determine the impact of different HP treatments on the microbial load and bacterial diversity of sous-vide Atlantic cod. Sous-vide cooking at 57.1 °C for 30 min followed by HP treatment at 500 MPa for 8 min reduced viable cell counts (total aerobic mesophiles) in the cod samples below detectable levels for 45 days of storage under refrigeration. In a second trial with cod cooked sous-vide at 52 °C for 20 min followed by HP treatments at 300 or 600 MPa (with HP treatment temperatures of 22 °C or 50 °C for 4 or 8 min, depending on treatment), only the treatments at 600 MPa delayed bacterial growth for at least 30 days under refrigeration. The optimal HP conditions to improve the microbiological quality of sous-vide cod cooked at low temperatures were obtained at 600 MPa for 4 min at a pressurization temperature of 50 °C. Bacterial diversity was studied in cod cooked sous-vide at 52 °C for 20 min by HTS. In the absence of HP treatment, Proteobacteria was the main bacterial group. A succession of Pseudomonadaceae (Pseudomonas) and Enterobacteriaceae was observed during storage. Firmicutes had low relative abundances and were represented mainly by Anoxybacillus (early storage) and Carnobacterium (late storage). The HP-treated sous-vide cod showed the greatest differences from controls during late storage, with Aerococcus and Enterococcus as predominant groups (depending on the HP conditions). The application of HTS provided new insights on the diversity and dynamics of the bacterial communities of sous-vide cod, revealing the presence of bacterial genera not previously described in this food, such as Anoxybacillus. The significance of Anoxybacillus as a contaminant of seafoods should be further investigated.

High-rate activated sludge at very short SRT: Key factors for process stability and performance of COD fractions removal

In high-rate activated sludge (HRAS) processes, reducing the solid retention time (SRT) minimizes COD oxidation and allows to obtain the maximum energy recovery. The aim of this research was to operate a pilot plant with an automatic control strategy to assure the HRAS process stability and high COD fractions removal at very low SRT. This study combines simulation and experimental tools (pilot plant 35 m3·d − 1) operating at SRT (0.2 d), HRT (0.6 h) and DO (0.5 mg·L − 1) treating high-strength raw wastewater, at 18–26°C, at variable flow. The research includes the effects of temperature, influent concentration and MLSS reactor concentration over the sCOD, cCOD and pCOD removal.The study points out that the best parameter to control the HRAS at a low SRT is not strictly the SRT but rather the reactor MLSS concentration: operating at 2,000±200mg·L − 1 assured a stable process despite the large influents variation. Low SVI values of 50–70ml·g − 1 indicated the good settling properties of the biomass. With only a 6.9% COD oxidation, a high organic matter removal (57±9% for COD and 56±10% for BOD5), was reached. The high removal efficiencies for pCOD (74%) compared to the (29%) for sCOD and (12%) for cCOD also confirmed the importance of settling efficiency and stability in the HRAS. The direct correlation between COD influent and COD removal makes advisable to use the HRAS as a replacement of the primary clarifier. The HRAS acted efficiently as a filter for COD and pCOD peak loads and, in a lesser extent, for BOD5, while sCOD peaks were not buffered. The adopted model presented a good fit for COD fractions except for pCOD when the temperature exceeds 23 °C.

HIGH TURBIDITY AND COD REMOVAL IN RIVER WATER USING LOW DOSAGE PLANT-BASED TACCA LEONTOPETALOIDES FLOCCULANT (TBPF) FOLLOWED BY ACTIVATED CARBON TREATMENT

Pollution in river water affects human, plant and animal health and activities, and its removal using chemical coagulants is a huge concern. This study aims to reduce turbidity and COD pollutants in river water through coagulation-adsorption process by using Tacca leontopetaloides biopolymer flocculant (TBPF) and powder activated carbon (PAC). In coagulation experiment, TBPF dosages were varied to evaluate the effect on turbidity and COD removal in river water by using Bioblock flocculator followed by adsorption process by adding PAC. The results found that at 200 mg/L of TBPF dosage with 2000 mg/L of PAC, the maximum turbidity and COD removal were obtained at 49% and 81%, respectively. The final turbidity and COD loads were 4.2 NTU and 9.3 mg/L, respectively, which were below the standard limit set for CLASS IIB provided by the National Water Quality Standards of Malaysia (NWQSM). High turbidity and COD removal using low dosage of environmental friendly plant-based TBPF-PAC through coagulation-adsorption process in this study has a great potential for river water treatment, particularly at the domestic area.

High-resolution mapping of the rainfall runoff pollution: case study of Shiwuli River watershed, China.

Rainfall runoff is the key factor of water quality deterioration in highly urbanized area, which is characterized by intensive human activities and frequent extreme weather events. Urban landscape system is composed of highly diverse and heterogeneous land patches, which makes the effective management of urban runoff pollution difficult. Therefore, high-resolution land-use data is imperative for the identification and analysis of spatial-temporal characteristics of urban runoff pollution. In this study, Shiwuli River watershed, a rapidly urbanizing area in China, is selected as the study area. We first interpret nine kinds of land-use types with a high-resolution remote sensing data of 2m [Formula: see text] 2m. Then, a localized Soil Conservation Service model based on field observation and rainfall experiments is applied to map the spatial-temporal pattern of runoff pollution. The results indicate that the COD, NH3-N, TP, and TN load generated by the runoff in the watershed accounted for 23.4%, 3.7%, 8.2%, and 9.0% of the total pollution load in 2016, respectively. Furthermore, the spatial-temporal pattern of the assessed runoff pollution was mainly subject to the distribution of rainfall and land-use patterns. We suggest that the sponge city construction combined with surface pollution control is an effective way to reduce the runoff pollution. This study highlights the necessity to identify spatial-temporal hotspots in developing precise pollution control measures, which provides valuable information for pollution control policy-making in Shiwuli River watershed and could serve as a reference for other river watersheds undergoing rapid urbanization.