Combined Sewer Research Articles

Analysis of suspended solids emissions from a combined sewage system using the Stormwater Management Model (SWMM)

The protection of water bodies requires the reduction of pollutant emissions from all major sources. In urbanized areas, these include: wastewater treatment plants (WWTPs) and (depending on the type of sewage system) combined sewer overflows (CSOs) and stormwater drainage outlets. WWTPs are usually monitored and emitted pollutant loads are known, but it is more difficult to assess the pollutant load discharged by CSOs and stormwater drainage systems. The article attempts to use the Stormwater Management Model (SWMM) to assess emissions of suspended solids from a large urban combined catchment. Suspended solids are the main pollutant of stormwater runoff in urban areas, and the dynamics of their emission from catchments is very diverse. The amount of suspended solids discharged by CSOs functioning in the given city was assessed in comparison with emissions from a wastewater treatment plant. The results show that CSOs discharge a pollutant load to the receiver which is comparable to WWTPs, but in a much shorter time and in a violent manner which can lead to the severe deterioration of receiving water quality. The modelling took into account the quality of dry weather sewage, the build-up of suspended solids, wash-off processes in the catchment area, and local precipitation characteristics. Factors affecting the quality of the obtained model and the accuracy of the emission level assessment were analysed.

Effects of urban catchment characteristics on combined sewer overflows

Pollution from Combined Sewer Overflows (CSOs) cause diffuse environmental problems, which are still not satisfactorily addressed by current management practices. In this study, a sensitivity analysis was conducted on several CSO environmental impact indicators, with respect to parameters that characterise climate, urban catchment and the CSO structure activation threshold. The sensitivity analysis was conducted by running 10000 simulations with the Storm Water Management Model, using a simplified modelling approach. The indicators were calculated at yearly scale to evaluate overall potential effects on water bodies. The results could be used to estimate pollution load ranges, known the values of the input parameters, and to investigate suitable strategies to reduce pollution of the receiving water bodies. The percentage of impervious surface of the catchment was found the most influent parameter on all the indicators, and its reduction can contain the discharged pollutant mass. The activation threshold, instead, resulted the second least influent parameter on all the indicators, suggesting that its regulation alone would not be a suitable strategy to reduce CSO pollution. However, along with the reduction of the imperviousness, its increase could effectively decrease the concentration of pollutant in the overflow. The results also indicate that neither adopting sustainable urban drainage practices, nor interventions on the CSO device, significantly affect the frequency of the overflows. Therefore, restricting this latter was found to be ineffective for the reduction of both the discharged pollutant mass and the concentration of pollutant in the overflow.

Municipal wastewater monitoring revealed the predominance of blaGES genes with diverse variants among carbapenemase-producing organisms: high occurrence and persistence of Aeromonas caviae harboring the new blaGES variant blaGES-48.

We characterized carbapenemase-producing organism (CPO) detected in municipal wastewater to better understand the epidemiology of CPOs in the community. In total, 36 samples were collected at six sampling sites every other month from December 2020 to October 2021. CPOs were not recovered from influent taken from inlet A receiving separated sewer line, treated effluents, and river water samples upstream and downstream of the effluent outlet. By contrast, 75 CPOs were detected in all influent samples taken from inlets B and C receiving combined sewer lines collecting both domestic/industrial wastewater and rainwater runoff. Aeromonas caviae was the dominant species (25/75, 33.3%), and the other 11 Aeromonas spp. together accounted for 48% of CPOs. The remaining 39 Enterobacterales strains mainly comprised 17 Klebsiella spp. and 10 Raoultella spp. CPOs carrying blaGES carbapenemase genes were overwhelmingly dominant, accounting for 72 of 75 isolates, including two isolates harboring both blaGES-24 and blaIMP-1 (96%), followed by three blaIMPs-positive isolates, where those carbapenemase genes were mainly carried in diverse class 1 integrons. Among blaGES variants, including six new variants (blaGES-47, blaGES-48, blaGES-49, blaGES-50, blaGES-51, and blaGES-54), blaGES-5 was detected in 28 CPOs, with Aeromonas spp. accounting for 53.6% of these organisms. Quantitative analysis revealed that the repeated detection of blaGES-48-positive A. caviae ST1056 from both inlets B and C ranked the total number of this bacterial clone highest in the wastewater influent. In summary, our study revealed the high prevalence and persistence of diverse blaGES carbapenemase genes among CPOs isolated from influent inlets connected to combined sewer systems.IMPORTANCEThe emergence and spread of carbapenemase-producing organisms (CPOs) represent a global health threat because they are associated with limited treatment options and poor clinical outcomes. Wastewater is considered a hotspot for the evolution and dissemination of antimicrobial resistance. Thus, analyses of municipal wastewater are critical for understanding the circulation of these CPOs and carbapenemase genes in local communities, which remains scarcely known in Japan. This study resulted in several key observations: (i) the vast majority of blaGES genes, including six new blaGES variants, and less frequent blaIMP genes were carbapenemase genes encountered exclusively in wastewater influent; (ii) the most dominant CPO species were Aeromonas spp., in which a remarkable diversity of new sequence types was observed; and (iii) CPOs were detected from combined sewer wastewater, but not from separate sewer wastewater, suggesting that the load of CPOs from unrecognized environmental sources could greatly contribute to their detection in influent wastewater.

Somatic Coliphages as an Operational Tool to Assess Loss of Bathing Water Quality after Heavy Rain Events

Rapid population growth and coastal development has led to increased fecal contamination of coastal surface waters worldwide, enhancing the potential risk of waterborne human pathogens in bathing areas. More frequent heavy rainfall events, attributed to global warming, have further exacerbated the problem by causing sometimes sewer overflows into recreational waters. As traditional bacterial indicators have limited accuracy for predicting health risks associated with waterborne viruses, the additional use of viral indicators such as coliphages is recommended. In this study, we compared the behavior of bacterial and viral indicators of water quality at 10 Barcelona beaches during three bathing seasons, in dry conditions, and after four rainstorms that caused specific pollution events due to rain runoff with combined sewer overflows (CSO). Levels of all target indicators increased after the rainstorms, but compared to Escherichia coli and intestinal enterococci, somatic coliphages exhibited a slower decline and higher environmental persistence following a rain event. Daily continuous sampling carried out during the days following a rainstorm allowed not only the determination of the decay kinetics of each target indicator but also the day when the water quality recovered the values established in the current European regulation in approximately 2 -3 days after each CSO. These observations indicate that the combined use of bacterial and viral indicators can enhance the surveillance of microbial quality of bathing waters. Moreover, coliphages can swiftly provide insights into transient fecal pollution linked to rainfall episodes, thanks to available analytical techniques that enable same-day recommendations. The management of urban wastewater and recreational water regulations should consistently employ microbial indicators to address rainwater runoff or sewer overflows resulting from heavy rainfall.

Missing methane emissions from urban sewer networks

Methane emissions from sewer networks are an important source of anthropogenic greenhouse gases (GHGs) but are not currently reflected in the national GHG inventory. We found significant CH4 emissions of approximately 573 [395–831] CH4 t y−1 from sewer networks in the old residential and commercial areas of Seoul (Gwanak district) using an electric vehicle-based atmospheric GHG monitoring platform. The majority of ethane-to-methane ratios (<0.005) from the observations further suggest that distinctive CH4 emissions from sewer networks are likely related to microbial activity rather than to simple natural gas leakage. Because over 90% of the sewer network in Seoul is a gravity drain type of combined sewer network, where both wastewater and stormwater flow through the same pipes, resulting in the generation of methane emissions from the microbial activity and the manholes and rain gutters, which are directly connected to the combined sewer networks are major sources of atmospheric methane emissions. This study suggests that appropriate treatment of sewer networks can mitigate missing methane emissions in cities that were not originally included in GHG inventory of South Korea.

Pollution load assessment in the form of TSS and COD emitted from an urbanized catchment in the aspect of administrative pollutant discharge fees on the example of the activity of the J1 CSO in Lodz (Poland)

The article presents the possibility of reducing fees for wastewater discharge from combined sewer overflows (CSOs) into the aquatic environment by minimizing the load emission of total suspended solids (TSS) and chemical oxygen demand (COD). The analysis was conducted based on limiting the wastewater volume discharged to the receiving water by one of the viable options, i.e., raising the overflow crest. The assessment was made on the example of the functioning J1 CSO in Lodz (in Polish: Łódź) in the years 2013–2015. An analysis of rainfall recorded in the J1 catchment area was also performed for this period. For the determination of the TSS and COD load emitted to the receiver, a predictive model based on rainfall parameters and the volume of discharged wastewater was used. To determine the wastewater volume emitted during individual activations of the J1 overflow, the model of the sewer network serving this catchment was calibrated in the EPA SWMM software. Simulations were conducted, considering different heights of the weir crest (static change). The results of the analyzes showed that raising the crest by 5 cm reduced the total fee for the J1 activity by 35% compared to its existing height in 2013 and about 40% for 2015. Raising the crest by 10 cm in 2015 enabled, for example, the J1 overflow activity to be in accordance with the applicable law. Reducing the amount of wastewater discharged to the receiver by using the overflow crest height adjustment method presented in the article may bring measurable financial and ecological benefits.

Comparison of leaching behaviour of heavy metals from sediments sampled in sewer systems - environmental and public health aspect.

The article analyzes the content of heavy metals and standard physical as well as chemical pollution indicators in different types of sediments from stormwater, combined sewer and sanitary sewer systems. Nickel, lead, chromium, copper, zinc and cadmium, as well as standard physical and chemical pollution indicators, were determined in sewage sediments. Aqueous extracts of sediments samples, taken from storm water sewer inlet sediments traps, storm sewers, sanitary sewers and combined sewers, were prepared in accordance with PN-EN 12457-2:2006. After mineralization, the concentrations of the metals: nickel, lead, chromium, copper, zinc and cadmium in the extracts were determined using the inductively coupled plasma emission spectroscopy technique. The results were analyzed with a non-metric multidimensional scaling algorithm. The heavy metal content was variable depending on the sediments collection site. The heavy metals nickel, lead, chromium, copper, zinc and cadmium were found in the sediments from stormwater inlets, storm sewer and sanitary sewer channels, with variability in the concentration of individual metals. The sediments from the flushing of sanitary sewers and combined sewers did not contain cadmium. The content of heavy metals in sediments varied depending on the sampling location and type of sewer system, indicating the need for detailed monitoring to identify the sources of emissions. Sediments from stormwater sewers have higher concentrations of heavy metals, with those from sewer inlets showing zinc concentrations exceeding regulatory limits, highlighting the variability and potential environmental impact of different sewer systems.

Potential for Conduit Hydropower at NYC's Newtown Creek Wastewater Treatment Plant

The Newtown Creek facility is New York City's largest wastewater treatment plant, with the capacity to treat up to 2.65 billion liters of combined sewage (rainfall and raw sewage) each day. After treatment at the plant, clean water flows out to the nearby East River via an outfall pipe. On average, the plant treats 810 million liters of combined sewage per day, which means there is potential to extract significant amounts of energy from the water flowing through the outfall. This paper first verifies that hydropower is a viable option at the plant by calculating the theoretical amount of power available from the running water, then determines what type of turbine would be the most appropriate for the outfall, and finally calculates how much electricity could realistically be generated by a turbine in the outfall. The bulb turbine was identified as the most appropriate type of turbine, and it was approximated that a bulb turbine in the outfall could produce, on average, 263 kilowatts of power. Considering that the plant runs year-round, a total of 2.24 gigawatt hours of clean electricity could be generated annually, which could be used to help power the energy-intensive wastewater treatment process or be fed back into New York City's electrical grid, where it could power up to 211 homes annually.

Improving the interpretability of deep reinforcement learning in urban drainage system operation

Deep reinforcement learning (DRL) has been increasingly used as an adaptive and efficient solution for real-time control (RTC) of the urban drainage system (UDS). Despite the promising potential of DRL, it is a black-box model whose control logic and control consequences are difficult to be understood and evaluated. This leads to issues of interpretability and poses risks in practical applications. This study develops an evaluation framework to analyze and improve the interpretability of DRL-based UDS operation. The framework includes three analysis methods: Sobol sensitivity analysis, tree-based surrogate modelling, and conditional probability analysis. It is validated using two different DRL approaches, i.e., deep Q-learning network (DQN) and proximal policy optimization (PPO), which are trained to reduce combined sewer overflow (CSO) discharges and flooding in a real-world UDS. According to the results, the two DRLs have been shown to perform better than a rule-based control system that is currently being used. Sobol sensitivity analysis indicates that DQN is particularly sensitive to the flow of links and rainfall, while PPO is sensitive to all the states. Tree-based surrogate models effectively reveal the control logic behind the DRLs and indicate that PPO is more comprehensible but DQN is more forward-looking. Conditional probability analysis demonstrates the potential control consequences of the DRLs and identifies three situations where the DRLs are ineffective: a) the storage of UDS is fully utilized; b) peak flows have already passed through actuators; c) a substantial amount of water enters one location simultaneously. The proposed evaluation framework enhances the interpretability of DRL in UDS operations, fostering trust and confidence from operators, stakeholders, and regulators.

Forecasting and optimization for minimizing combined sewer overflows using Machine learning frameworks and its inversion techniques

Combined sewer overflows (CSOs), which typically occur during heavy rainfall events, pose significant threats to both public health and the environment. These threats encompass various concerns, including contamination of drinking water. Numerous studies have developed strategies aimed at mitigating the adverse effects of CSOs. These strategies include Green Infrastructure, Integrated Planning, and Smart Control Strategies. Among these, Smart Control Strategies have gained the most traction due to their exceptional cost-effectiveness. Nevertheless, the existing control methods face a challenge in striking the right balance between precision and computational efficiency. While employing full numerical methods as predictive models can provide high accuracy, they often prove inefficient in terms of runtime, especially when applied to real-world complex combined sewer systems. Conversely, reduced-order models tend to offer quicker results but may sacrifice accuracy. To address this issue, we propose an exploration of various mainstream machine learning models for CSO predictions. Additionally, we introduce a novel approach known as “inversion of neural networks” to bridge the gap between prediction and optimization. This innovative method enables us to use a single neural network for both CSO prediction and optimization tasks, resulting in a significant enhancement in terms of computational efficiency. The accuracy of our predictive approach has been validated through simulation results. In terms of optimization performance, it provides similar outcomes to the genetic algorithm, while significantly improving computational speed.

Small villages and their sanitary infrastructure—an unnoticed influence on water quantity and a threat to water quality in headwater catchments

In rural catchments, villages often feature their own, separate urban water infrastructure, including combined sewer overflows (CSOs) or wastewater treatment plants (WWTPs). These point sources affect the water quantity and quality of the receiving low order streams. However, the extent of this impact is rarely monitored. We installed discharge and water quality measurements at the outlet of two small, neighbouring headwater catchments, one that includes a village, a WWTP, and two CSOs, while the other is predominantly influenced by agricultural activities. We also deployed electrical conductivity (EC) loggers at the CSOs to accurately detect discharge times. Discharge from the WWTP and CSOs led to higher peak flows and runoff coefficients during events. Less dilution of EC and increasing ammonium-N (NH4 − N) and ortho-phosphorus (oPO4 − P) concentrations indicate a significant contribution of poorly treated wastewater from the WWTP. During CSO events, water volumes and nutrient loads were clearly elevated, although concentrations were diluted, except for nitrite-N (NO2 − N) and particulate phosphorus (PP). Baseflow nitrate-N (NO3 − N) concentrations were diluted by the WWTP effluent, which led to considerably lower concentrations compared to the more agriculturally influenced stream. Concentrations of oPO4 − P, NH4 − N, and NO2 − N, which are most likely to originate from the WWTP, vary throughout the year but are always elevated. Our study shows the major and variable impact rural settlements can have on stream hydrology and water quality. Point sources should be monitored more closely to better understand the interaction of natural catchment responses and effects caused by sanitary infrastructure.

What is hiding below the surface – MPs including TWP in an urban lake

Inland lakes play an important role as habitats for local species and are often essential drinking water reservoirs. However, there is limited information about the presence of microplastics (MPs) in these water bodies. Thirteen sediment samples were collected across a Danish urban lake to map MPs, including tyre wear particles (TWP). The lower size detection limit was 10 µm. MPs were quantified as counts, size, and polymer type by Fourier-transform infrared microspectroscopy (µFTIR) and mass estimated from the 2D projections of the MPs. As TWP cannot be determined by µFTIR, counts and sizes could not be quantified by this technique. Instead, TWP mass was determined by pyrolysis gas chromatography mass spectrometry (Py-GC/MS). The average MP abundance was 279 mg kg−1 (µFTIR), of which 19 mg kg−1 (Py-GC/MS) were TWP. For MPs other than tyre wear, the average MP count concentration was 11,312 counts kg−1. Urban runoff from combined sewer overflows and separate stormwater outlets combined with outflow from a wastewater treatment plant were potential point sources. The spatial variation was substantial, with concentrations varying several orders of magnitude. There was no pattern in concentration across the lake, and the distribution of high and low values seemed random. This indicates that large sampling campaigns encompassing the entire lake are key to an accurate quantification. No preferential spatial trend in polymer characteristics was identified. For MPs other than TWP, the size of buoyant and non-buoyant polymers showed no significant difference across the lake, suggesting that the same processes brought them to the sediment, regardless of their density. Moreover, MP abundance was not correlated to sediment properties, further indicating a random occurrence of MPs in the lake sediments. These findings shed light on the occurrence and distribution of MPs, including TWP, in an inland lake, improving the basis for making mitigation decisions.

Model-based prediction of bathing water quality in a lake polluted by fecal coliform bacteria from combined sewer overflows

In the European Union, recreational water quality is regulated by the bathing water directive, which requires authorities to regularly take water samples to identify fecal bacterial pollution, which can compromise the bathing water quality at designated recreational bathing water areas. Using a case study from Lake Knudsøin Denmark, this paper shows that the bathing water quality occasionally is compromised by overflows from combined sewer systems. Due to the randomness in the frequency of overflow occurrences, the entailing decrease in bathing water quality is not normally detected by the regulatory sampling campaigns. By dedicated sampling campaigns conducted in this project in the proximity of outlets and recreational bathing areas and by hydrodynamical transport modeling, it is shown that the transport patterns of pollutants are crucially and rapidly dependent on dynamic conditions. The occasional short-term pollution by fecal bacteria and consequent decrease in bathing water quality are, therefore, challenging to capture (both spatially and temporally) by regular water sampling. Rather than increasing the frequency of water sampling, an online model-based warning system for fecal bacteria contamination in bathing areas is proposed. This warning system framework includes: (1) dynamical modeling of combined sewer overflow based on rainfall over a catchment area, (2) a hydrodynamical model that simulates current fields in multiple vertical layers based on wind forcing and water fluxes, and (3) a particle dispersion model which provides an estimate of pollutant concentrations. The output from the model has shown potential to issue bathing prohibition if there is a risk of fecal bacteria concentrations below the criteria for good bathing water quality.

A probabilistic-deterministic approach for assessing climate change effects on infection risks downstream of sewage emissions from CSOs

The discharge of pathogens into urban recreational water bodies during combined sewer overflows (CSOs) pose a potential threat for public health which may increase in the future due to climate change. Improved methods are needed for predicting the impact of these effects on the microbiological urban river water quality and infection risks during recreational use. The aim of this study was to develop a novel probabilistic-deterministic modelling approach for this purpose building on physically plausible generated future rainfall time series. The approach consists of disaggregation and validation of daily precipitation time series from 21 regional climate models for a reference period (1971–2000, C20), a near-term future period (2021–2050, NTF) and a long-term future period (2071–2100, LTF) into sub-daily scale, and predicting the concentrations of enterococci and Giardia and Cryptosporidium, and infection risks during recreational use in the river downstream of the sewage emissions from CSOs. The approach was tested for an urban river catchment in Austria which is used for recreational activities (i.e. swimming, playing, wading, hand-to-mouth contact). According to a worst-case scenario (i.e. children bathing in the river), the 95th percentile infection risks for Giardia and Cryptosporidium range from 0.08 % in winter to 8 % per person and exposure event in summer for C20. The infection risk increase in the future is up to 0.8 log10 for individual scenarios. The results imply that measures to prevent CSOs may be needed to ensure sustainable water safety. The approach is promising for predicting the effect of climate change on urban water safety requirements and for supporting the selection of sustainable mitigation measures. Future studies should focus on reducing the uncertainty of the predictions at local scale.

Ecological assessment of combined sewer overflow management practices through the analysis of benthic and hyporheic sediment bacterial assemblages from an intermittent stream

Combined sewer overflows (CSO) are used to avoid overloading unitary sewers and wastewater treatment plants. Following the European Council Directive on Urban Wastewater Treatment (UWT), CSO discharges are regulated using guidelines that aim to reduce their ecological impact on aquatic systems. A model CSO, which is part of a long-term experimental field observatory, was modified according to these guidelines and used to evaluate the benefits of compliance through analyses of the bacteriological and chemical states of the receiving intermittent stream. The benthic and hyporheic sediments of similar geomorphic units located upstream and downstream of a monitored CSO outlet were compared before and after changes in CSO regimes. Hydrological, pollutants (Metal Trace Elements, MTE; Polycyclic Aromatic Hydrocarbons, PAH; fecal indicator bacteria, FIB), and tpm-based DNA meta-barcoding datasets resolving the occurrences of >700 bacterial species of nearly 200 genera were studied. The frequency of overflow was confirmed to have significantly decreased following the application of the UWT guidelines. Overflows became almost limited to periods of heavy summer thunderstorm events. These changes were not associated with a significant decrease in most of the surveyed MTE, PAH, and FIB among stream sediments, except for chromium. Ecological benefits were highlighted by significant changes in tpm-based meta-barcoding community patterns between the UWT compliant sampling period and the previous one. Bacterial community change point analyses confirmed this segregation in the meta-barcoding dataset according to hydrological indices such as the number of CSO events and discharged volumes. A significant decline in CSO bacterial taxa in the benthic and hyporheic sediments was observed. Thirty-four CSO indicator species were identified, including Aeromonas caviae, Aeromonas media, and Pseudomonas oleovorans. These indicators, often documented as opportunistic pathogens (to humans, animals or plants) and/or pollutant degraders, were proposed as ecological sentinels for the assessment of CSO impacts.

Contemplation of Improvement Efforts to Manage Combined Sewer Overflows

Combined sewer overflow (CSO) is a significant environmental concern and public health risk (e.g., water contamination, eutrophication, and beach closure). The Environmental Protection Agency (EPA) has introduced the National Pollutant Discharge Elimination System (NPDES) permitting program to regulate and address this matter. This program mandates the control of CSOs for more than 700 municipalities obligated to devise Long-term Control Plans (LTCPs) to curb combined sewer overflows and reduce them to safe levels. The LTCP involves diverse strategies, including sewer separation, green infrastructure improvements, and conventional gray infrastructure upgrades. This study investigates several municipalities’ solutions for CSO problems that use conventional methods and wireless sensor technology as real-time control, mainly focusing on a comparative analysis of two cities, Richmond, Virginia, and South Bend, Indiana, such as their average rainfall, the frequency of overflows, and the capacity of treatment plants. The findings indicate that integrating sensor technology could significantly enhance modeling endeavors, bolster the capacity of existing structures, and substantially enhance preparedness for storm events. The EPA’s Storm Water Management Modeling (SWMM) software is utilized. Through an analysis of SWMM data, the study suggests the potential for leveraging wireless sensor technology to achieve more robust control over CSOs and significant cost savings as a part of LTCPs.

Prevention of water pollution through combined sewer overflow using high-speed biofiltration in urban watershed

Over recent decades, the rural areas of Korea, including containing source waters, have become extensively developed. Combined sewer systems (CSSs) have been constructed to collect the sewage generated from these areas. Presently, it is common to experience localized heavy rain events, likely due to climate change, and sometimes, the volume of rainfall can become too high for a CSS to handle. In these cases, combined sewer overflow (CSOs) occurs, contaminating surface water, which may have been used as source water. Therefore, the Korean government will begin regulating the biochemical oxygen demand (BOD) of CSOs occurring during first flushes of less than 40 mg/L from 2024 onwards. In this study, a biofiltration-based technology was proposed to treat CSOs. Thus, this study aimed to remove BOD from CSO using this biofiltration system to contain cube-type media. For this, two different loading rates were tested on a pilot scale. Although the proposed system resulted in a footprint of only 10 % of that of a conventional activated sludge system, it was still capable of achieving efficient BOD removal. At a high loading rate, BOD removal efficiency was observed at approximately 53 %, and when this loading rate was reduced by 50 %, the removal efficiency was slightly improved to about 58 %. In both cases, the BODs of treated CSOs could be maintained below the proposed future standard: 31 mg/L and 28 mg/L for high and low loading rates, respectively. Therefore, the proposed system could potentially be preventing environmental contamination from COSs.

Effects of combined mineral and sewage sludge fertilization on soil properties and growth of two &lt;i&gt;Zea&lt;/i&gt; &lt;i&gt;mays&lt;/i&gt; (L.) varieties in Western Highlands of Cameroon

This study aimed at evaluating the effects of combined application of dewatered sewage sludge (SS) and mineral fertilizer on the chemical properties of the soil and growth of &lt;i&gt;Zea&lt;/i&gt; &lt;i&gt;mays&lt;/i&gt;. Six treatments: T0, negative control; T1, positive control of 120 kg N/ha; T2, 2 t/ha sewage sludge (SS) + 60 kgN/ha; T3, 4 t/ha SS + 60 kgN/ha; T4, 8t / ha SS+ 60 kgN/ha and T5, 8 t/ha SS were applied in completely randomized block experimental design. The following parameters: height of plants, diameter of stem, number of healthy leaves, leaves area index, root and shoot biomasses were measured on plants at 30, 44 and 58 days after sowing. For the soil parameters, electrical conductivity (EC), redox and hydrogen potentials were measured at the same frequency. The results showed that the height, the stem diameter, the number of leaves, the leaves area index and the biomass of Zea mays increased in response to soil supplementation with sewage sludge combined with mineral fertilizers. The treatment that best stimulated the growth of maize was T4 (8t/ha SS+ 60 kgN/ha). The soil chemical properties were modified by sewage sludge application. In general, pH and conductivity decrease with sludge application, while, redox potential increased. This shows that combined sewage sludge to NPK (20 10 10) leads to changes in chemical parameters of the soil and thus, influencing the nutrients uptake by plants to improve their growth.

A simple and rapid method for detecting fecal pollution in urban rivers by measuring the intrinsic β-D-glucuronidase activity of Escherichia coli

As urban rivers are domestic, industrial, and agricultural water resources, fecal pollution poses human health and environmental risks. In this study, we developed a simple and rapid method to detect fecal pollution in urban rivers. Water samples were mixed with liquid medium, including a fluorescent substrate and fluorescence intensity (F.I.) was measured using a microplate reader to determine Escherichia coli (E. coli) β-D-glucuronidase (GUS) activity instead of E. coli concentration. GUS activities measurements in pure E. coli cultures revealed that E. coli incubated with a GUS substrate accumulated GUS enzymes in their cells, whereas those incubated without a GUS substrate did not. The increase in GUS activity corresponded to the proliferation of E. coli and the GUS activity increased linearly even during the lag growth phase of E. coli, indicating the presence of intrinsic GUS (iGUS) in E. coli cells before incubation. iGUS activity persisted at 81 % in the chlorinated samples, even though the E. coli concentration was reduced by a factor of 106. The iGUS activity persisted for approximately three days. Therefore, we assumed that E. coli present in fecal contaminants, in which GUS substrates are present, could be distinguished from those surviving in the natural environment for three days or longer by measuring iGUS activity. River water samples were collected upstream and downstream of the discharge outlets of municipal wastewater treatment plants and a combined sewer outlet. The iGUS activities were <0.24 mMFU/mL for the upstream samples and >0.21 mMFU/mL for the downstream samples. Interestingly, E. coli concentrations were not necessarily associated with fecal pollution. This indicates that by setting a threshold for iGUS activity, our method can be used as a simple and rapid method for detecting fecal pollution in urban rivers. Because the limit of detection for our method is 20 CFU/mL, our method is applicable to detecting high fecal pollution in a small river.

Cloud-Based Artificial Intelligence Analytics to Assess Combined Sewer Overflow Performance

Cloud-Based Artificial Intelligence Analytics to Assess Combined Sewer Overflow Performance