Tertiary Treatment Unit Research Articles

Performance evaluation of integrated Upflow Anaerobic Sludge Blanket reactor with trickling filter used for municipal wastewater treatment and effluent reuse potential for agriculture

Effluent reuse is a rapidly growing field of research where assessing the quality of effluent is one of the focus areas. This research examines the viability of using wastewater in agriculture by testing an integrated Upflow Anaerobic Sludge Blanket (UASB) reactor with a trickling filter (TF) system during the dry season. Compliance monitoring was conducted for 30 days from May 11 to June 9 of 2021. Samples were collected, handled, and analyzed following standard wastewater analysis procedures for biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), volatile suspended solids (VSS), cations, anions, heavy metals, E. coli, and helminth egg. The UASB-TF system in Kality wastewater treatment performed well in removing COD, BOD5, and TSS with average removal rates of 80.5%, 82.9%, and 80.9%, respectively, compared well with similar treatment configurations. The effluent quality satisfied the national inland discharge limit with a residual concentration of 125.1 mg/L for COD, 61.7 mg/L for BOD5 and 85.8 mg/L for TSS. On the other hand, high concentrations of chromium, nitrate-nitrogen, and helminth egg count restricted effluent reuse for agricultural purposes due to high health risks and environmental contamination. We found out that discharging industrial sewage into the domestic sewer network could inhibit microbial growth and affect the biological treatment processes. Furthermore, adopting integrated treatment systems in developing countries might face operational challenges and monitoring nitrate, helminth egg, and heavy metals would help provide timely operational feedback. An appropriate tertiary treatment unit—constructed wetlands or polishing ponds—is therefore needed to be introduced to ensure effluent reuse for agricultural purposes.

Suppurative Cervicomediastinitis From the Perspective of the Head and Neck Surgeon in a Tertiary Treatment Unit.

Introduction Cervical suppurations represent an emergency pathology, with a dramatic evolution in the absence of adequate treatment. It frequently affects young people, hence the medico-legal implications of these cases. The anatomical substrate for the development of these deep cervical suppurations is represented by the cervical fascia and spaces. A distinct and extremely serious sub-chapter within diffuse cervical suppurations is necrotic cervical fasciitis, a polymicrobial infection with the most common oropharyngeal or odontogenic starting point, with rapidly progressive, destructive evolution in the deep fascial planes of the neck. Materials and method We will present a retrospective clinical study carried out on 26 cases diagnosed and treated between September 2013 and September 2018 in the ENT Clinic Department of the Bucharest University Emergency Hospital. Results Our retrospective analysis of a cohort of 26 patients in a tertiary referral center showed that deep cervical suppurations are slightly more common in men than in women. The most affected age groups were 50-59 years, followed by 20-29 years, representing a percentage of 53.84% of all cases. Also, 53.84% of the studied patients with deep cervical suppurations had a precarious and modest status. The most common clinical signs at presentation were malaise, cervical swelling, neck pain, dysphagia, fever, dysphonia, dyspnea, and cervical erythema. More than 60% of suppurations were odontogenic and 23% were caused by a traumatic element. Diabetes mellitus represents a comorbidity in 30.8% of patients, while 42.3% of patients had no personal pathological history, and thus this pathology has a lethal potential also in a patient in full health. In the study group, 46 (15%) had cervicomediastinitis, and 61.53% developed necrotizing fasciitis. One-third (34.61%) of our patients had undergone previous drainage surgery. Bacteriological examinations of the wound were with group C, D, G betahemolytic streptococcus, while 61.53% of the cultures were negative. Most patients required at least two cervicotomies. The average duration of hospitalization was 28.26 days, and the mortality rate was 23.07%; therefore, practically, one out of four cases resulted in death. In the studied group, no direct relationship can be established between the length of hospitalization and the favorable and unfavorable evolution of the patient. We propose a 10-step management protocol for the management of a cervical suppuration. Conclusion The multidisciplinary approach to these suppurations by the head and neck surgeon, the thoracic surgeon, the oromaxillofacial surgeon, anesthetist, imagist, specialist in infectious diseases, pathologist, psychologist, and so on, is the key to success in a patient who presents not only a suppuration in the throat but also a disease with systemic resonance and significant lethal potential.

Human health risk assessment and uncertainty analysis of silver nanoparticles in water.

Despite frequent detection in environmental waters, literature which quantifies the health risk of silver nanoparticles (Ag NPs) through oral ingestion is scarce. This study compiled literature data to find the removal of Ag NPs from different treatment schemes (i.e., natural, engineered, or hybrid). Ag NP concentrations were found either in surface water or in groundwater based on where the effluent of treatment schemes was discharged, i.e.,either in surface water or in groundwater. Monte-Carlo simulation was carried out for probabilistic assessment of health risks for children for two hypothetical exposure scenarios: (a) ingesting river water while swimming and (b) drinking groundwater. Bio-accessible fraction, dietary metal adsorption factor, and concentrations of silver ions were incorporated to simulate realistic situations. Different treatment schemes were ranked for their nanoparticles' removal efficiency with respect to (i) exceedance probability from guideline value and (ii) health risk to children. Hybrid treatment combinations, i.e., conventional primary and secondary treatment units followed by nature-based units (constructed wetlands and soil aquifer treatment), were ranked the best. The health risk value was found to be less than 1, with the 99th percentile value less than 10-3 in all cases. The maximum allowable concentration of Ag NPs was found to be as low as 1.43 mg/L for groundwater, suggesting probable potential for risk. Uncertainty analysis revealed that the uncertainty of the influent NPs concentration in raw wastewater contributes > 99% to the variance of the hazard index. The results of this work indicate that the use of natural treatment technologies with existing engineered treatments provides higher nanoparticle removal from wastewater without the requirement of any tertiary treatment unit.

Life cycle assessment of a common effluent treatment plant: Case study of Mahad, India

Common effluent treatment plants (CETPs) offer extensive benefits for wastewater treatment in developing countries in terms of cost-effectiveness, industrial synergy, and resource conservation. Evaluating the performance of CETPs is essential to ensure sustainable practices in wastewater management. The present study aims to assess the environmental impacts of a CETP situated in Maharashtra, India, using the life cycle assessment method (LCA) as per ISO 14040:14044. The plant comprises a primary, secondary, and tertiary treatment unit along with a sludge handling unit. The inventory analysis was performed using the averaged data collected from the plant for a year. The secondary inputs were taken from the GaBi 10.6 database suited to the Indian context. The study employed a gate-to-grave LCA approach and the functional unit was assumed to be 1000 m3 of treated water. The impact analysis was conducted with the help of the CML 2001: Aug 2016 method. It was found that the primary and secondary treatment units offered the highest environmental burden. Both the treatment units contribute about 70–80 % to all the categories except for ADP-elemental, where the contribution is about 98 %. Electricity was identified as a predominant factor contributing to the impacts under most midpoint categories except for ADP-elemental. A scenario analysis was undertaken to estimate the possibility of adapting to renewable energy to reduce environmental footprints. The impacts generated under such a scenario were lower than the original observations, except for the ADP–elemental category. The study emphasizes how LCA helps optimize areas under investigation and fosters sustainable treatment practices in wastewater treatment.

Bacterial cell immobilized packed bed reactor for the elimination of dissolved organics from biologically treated post-tanning wastewater and its microbial community profile

In conventional, the biologically treated tannery wastewaters are rich in dissolved organics and the application of reverse osmosis (RO) to biologically treated tannery wastewater was challenged with fouling and failure of RO membrane due to existence of lingering dissolved organic compounds. In present investigation the bacterial cell immobilized packed bed reactor (CIPBR) was operated to remove the dissolved organic compounds in biologically treated post-tanning wastewater to avoid membrane fouling in RO. The efficient microbial syndicate to eliminate dissolved organics in post-tanning wastewater was isolated and immobilized on to the carbon silica matrix (CSM) in the range of 2.98 ± 0.2 × 107 cells gm−1 of CSM and the same was used as a carrier matrix in the packed bed reactor. The CIPBR established the CODtot, CODdis and BOD removal efficiency by 61 ± 4%, 57 ± 4% and 87 ± 3% respectively with CODtot, CODdis and BOD remained in the treated wastewater as 236 ± 21 mg/L, 228 ± 21 mg/L, and 12 ± 3 mg/L under continuous operation. The removal of dissolved organic compounds from the post-tanning wastewater was confirmed using UV–Visible and FT-IR spectroscopic studies. Among the total microbial community, the phylum Proteobacteria played most abundant role with 48.47% of relative abundance for the removal of dissolved organics in biologically treated post-tanning wastewater. The significance of the study is to replace the tertiary treatment unit operation in the conventional ETP/CETP to remove dissolved organics in wastewater.

Application of a new baffled horizontal flow constructed wetland-filter unit (BHFCW-FU) for treatment and reuse of petrochemical industry wastewater

The shortage of water resources and generation of large quantum of wastewater has posed a significant concern to the environment and public health. Recent research on wastewater treatment has started to focus on reusing wastewater for different activities to reduce the stress on natural water resources. Constructed wetland (CWs) is a low-cost wastewater treatment option. However, some drawbacks include large areal requirements and the need for tertiary treatment units for reusable effluent. In this study, a novel composite baffled horizontal flow CW filter unit (BHFCW-FU) was developed to overcome the drawbacks of the conventional CW. The BHFCW-FU planted with Chrysopogon zizanioides provided a nine times longer flow path, and the adjoined variable depth dual media filter reduced the total area requirement and served as a polishing unit. On average, the BHFCW-FU with horizontal sub-surface flow regime could efficiently remove around 93.93%, 87.20%, and 66.25% of turbidity, phenol, and COD, respectively, from real petrochemical wastewater (initial turbidity: 29.6 NTU, phenol: 4.52 mg/L, and COD: 381 mg/L) and rendered the effluent quality reusable for irrigation, industrial, and other environmental purposes. In synthetic wastewater (initial turbidity: 754 NTU, phenol: 10.87 mg/L, and COD: 1691 mg/L), the removal efficiency of turbidity, phenol, and COD were 99.50%, 93.73%, and 87.05%, respectively. In-depth substrate characterization was done to study the removal mechanism. The developed BHFCW-FU required less space and maintenance, provided reusable effluent, and overcame the drawbacks of conventional CWs. Hence, it may show immense potential as an effective wastewater treatment.

Design of hydrodynamic cavitation assisted intensified tertiary treatment unit for effective degradation of organic micropollutants in pharmaceutical industrial effluent: A Case study with triclosan

Increasing occurrence of micropollutants and trace amount of persistent organic contaminants (POC's) in the wastewater streams even after the well-established conventional treatment is a threat to human health, aquatic entities, and constitute a formidable challenge for the ecological security. In this regard, hydrodynamic cavitation based advanced oxidation treatment has attracted extensive attention towards removal of such micro scale pollutants from wastewater streams in the present scenario. Hence, the present work demonstrates the design and application of a rotating hydrodynamic cavitation (RHC) reactor with stator-rotor arrangement for effective degradation of organic micropollutants (triclosan being taken as the target pollutant) from tertiary effluents occurring in the pharmaceutical sector. The process performance was evaluated through optimization of geometric parameters of the reactor, various operating parameters as well as by studying the sole and synergistic performance of the HC process combined with other AOPs. The maximum degradation of Triclosan (TCS) achieved by RHC alone was found to be 35.2 % and in synergism, with ozone, a maximum of 97.6 % degradation was observed. Further, to ensure the mineralization of the components, total organic carbon (TOC) contents of the samples were measured and the degradation pathway was predicted through LC-MS analysis. The techno-economic feasibility of the process were understood through economic and energetic analysis and technology transfer was done for replicating the same study for a pilot scale reactor.

Biosorption of Cd(II) by Nordic microalgae: Tolerance, kinetics and equilibrium studies

The amount of heavy metals released into the environment has significantly increased. Industrial wastewaters, e.g. from mining or battery manufacturing, are often polluted with heavy metals such as Cd, Cr or Pb. These metals threat the environment and can cause health problems even at low concentrations. Therefore, their proper removal from industrial wastewater before its disposal is of paramount importance (Javanbakht et al. [1]). Here the ability of fourteen wild Nordic microalgal strains to remove cadmium (Cd(II)) from aqueous solutions has been studied. Three of the chosen strains, namely Chlorella vulgaris (13-1), Coelastrella sp. (3-4) and Scenedesmus obliquus (13-8), demonstrated high tolerance towards Cd(II) concentrations up to 2.5 mg L−1 and their sorption kinetics and equilibrium were studied. Metal sorption by Chlorella vulgaris (13-1) and Coelastrella sp. (3-4) was described best by pseudo-second order kinetics, whereas the removal kinetics of Scenedesmus obliquus (13-8) was best fitted by the intraparticle diffusion model. Starting from an initial concentration of 2.5 mg L−1Chlorella vulgaris (13-1) and Coelastrella sp. (3-4) removed 72% and 82%, respectively, of the Cd(II) within only 24 h. Modeling their Cd(II) sorption equilibria revealed that the SIPS- and Dubinin-Radushkevich models were best suited for living microalgae, and the maximum adsorption capacity (qmax) was calculated. While Chlorella vulgaris (13-1) and Coelastrella sp. (3-4) were able to remove about 49 mg g−1 and 65 mg g−1 Cd(II), respectively, Scenedesmus obliquus (13-8) only removed around 25 mg g−1. Fourier-Transform Infrared Spectroscopy (FTIR) analyses of the biomass revealed the carboxylic moieties of the cell wall to be the key player in Cd(II) removal. This study demonstrates the high potential of Nordic microalgae to remove heavy metals at conditions relevant for an industrial tertiary wastewater treatment unit and will support the development of new, biobased, innovative technologies for the bioremediation of heavy metal polluted streams.

Enhancing Microplastics Removal from Wastewater Using Electro-Coagulation and Granule-Activated Carbon with Thermal Regeneration

Discharge from sewage treatment plants (STPs) is a significant pathway of entry for microplastics (MPs) to the environment. Therefore, STPs should be considered as an important barrier to the distribution and circulation of MPs in the aquatic environment. In this study, the fate and material-specific properties of MPs were investigated in an STP-equipped and granule-activated carbon (GAC) tower with a thermal regeneration system. This system functioned with a tertiary treatment unit. The GAC with thermal regeneration removed 92.8% of MPs and was useful for removing MPs with a specific gravity less than that of water and with a size of 20–50 µm, which had negligible removal in the conventional STP process. In addition, a lab-scale electric-coagulation experiment was conducted to examine its potential utility as a pretreatment process for further enhancing the removal efficiency of MPs by GAC. After 30 min of electro-coagulation using aluminum electrodes, 90% of MPs were converted into separable flocs by centrifugation. These flocs may be effectively removed by GAC or other tertiary treatment steps. This study demonstrates that GAC with thermal regeneration is a tertiary process that can efficiently prohibit the release of MPs from STPs and circulation of MPs in the natural environment.

Treatment of wastewater with modified constructed wetland system as a tertiary treatment unit

Incorporation of constructed wetlands into the sewage treatment process is done in order to mimic processes found in the natural ecosystems where wetland plants and their associated microorganisms remove pollutants from wastewater. Vegetation in a wetland provides a substrate upon which microorganisms can grow, and break down organic materials. These organisms and natural chemical processes are responsible for approximately 90% of pollutant removal and waste breakdown in nature. This research work has been undertaken with a view to integrating the natural ecosystem into the existing treatment plant on a large scale, which will be instrumental in minimising the use of machineries and reducing high investment and operating cost as well as energy consumption. The greywater can be reused for purification but the currently adopted process to obtain a secondary water source is complicated and expensive. The conventional process constructed wetlands can be used as a tertiary treatment unit of sewage treatment process.

Treatment of wastewater with modified constructed wetland system as a tertiary treatment unit

Treatment of wastewater with modified constructed wetland system as a tertiary treatment unit

Occurrence and risk assessment of fluoroquinolone antibiotics in reclaimed water and receiving groundwater with different replenishment pathways

Artificial recharge to groundwater with reclaimed water is considered a promising method to alleviate groundwater depletion and over-exploitation. However, the occurrence of fluoroquinolone antibiotics (FQs) was ubiquitous in wastewater, surface water, groundwater and even drinking water threating human health and ecology. In this study, the occurrence of six selected FQs in reclaimed water effluent and their removal by tertiary treatment units were investigated. The overall removal efficiencies in average of the tertiary treatment processes in Beijing and Changzhou were ranging from 21.2% to 55.2%. Activated carbon exhibited better performance for FQs removal than ozone and biological treatment such as membrane bioreactor, anaerobic-anoxic-oxic and biofilter. The results of two pilot study showed that the impact of reclaimed water to groundwater quality in terms of FQs concentration by direct injection in GBD was stronger than surface spreading in Changzhou, which might be due to the recharge strategy and the physical and chemical characteristics of sediment and aquifer soil. The hazard quotient (HQ) values of ofloxacin (OFL) in reclaimed water was up to 12.54, indicating the extreme eco-toxicological risk, while enrofloxacin (ENR) exhibited medium risk. After recharge with reclaimed water, the HQ values of OFL and ENR in groundwater ranged from low to medium ecological risk to the environment. Thus, the FQs in reclaimed water need to be paid more attention during their reuse for groundwater recharge, especially by direct injection. It is suggested that FQs should be considered in the priority substances lists in standards and guidelines of reclaimed water reuse for groundwater recharge to ensure the safety of groundwater.

Effect of treated sewage characteristics on duckweed biomass production and microbial communities

Duckweed biomass production in a duckweed pond fed with three differently treated sewage (i.e. sewage treated by primary sedimentation (PS); conventional activated sludge process (CAS); and downflow hanging sponge process (DHS)) was evaluated in order to assess the effects of water quality on biomass yield. Higher and stable biomass production was observed when the duckweed pond was fed with PS or DHS-effluent than with CAS-effluent, evidently due to the difference in nutrient loads. Availability of nutrients, especially phosphorus, affected the biomass production rate: higher the nutrient, faster the production. Microbial community analysis revealed that the members of Rhizobiales were likely to contribute to stable and high biomass growth. From the results of the study, a sewage treatment system consisting of a primary sedimentation followed by a duckweed pond and a tertiary treatment unit can be proposed to maximize biomass production without compromising treatment objectives. Size and operational parameters of the duckweed pond should be determined primarily based on the nutrient availability in the influent water to maximize duckweed growth.

Impact of activated sludge bulking and foaming on the quality of Kuwait’s irrigation water

Treated municipal wastewater produced in Kuwait is used mainly in agricultural and landscape irrigations. However, there are strong doubts that severe sludge bulking and foaming problems, particularly during winter seasons, may render this water unsuitable for irrigation purposes. To assess the impact of these problems on the quality of irrigation water in Kuwait, samples of secondary and tertiary effluents and sludge-mixed liquor were collected weekly from two wastewater treatment plants for nine months. Routine wastewater quality parameters were then determined for the collected influent and effluent samples. Further, dominant filamentous bacteria in the sludge-mixed liquor samples collected from the aeration tanks were also identified and quantified using a molecular method called Vermicon Identification Technology (VIT). Obtained results of the effluents’ qualities were then statistically analyzed and compared to Kuwait’s irrigation water standards. Statistical results indicated that secondary effluents were greatly impacted by sludge bulking and foaming problems, while tertiary effluents were slightly affected. This finding highlights the importance of having tertiary treatment units in plants to encounter sludge bulking and foaming problems.

Characteristics of a hepatitis C patient cohort at a specialized tertiary care facility: Identifying criteria to improve the allocation of public health resources

OBJECTIVES:Our objective was to analyze, in a population treated for hepatitis C infection at a tertiary care treatment unit, the prevalence of comorbidities and extrahepatic manifestations, the range and degree of the clinical complexity and the associations between advanced liver disease and clinical variables.METHODS:Medical records from chronically infected hepatitis C patients seen at a dedicated treatment facility for complex cases in the Infectious Diseases Division of Hospital das Clínicas in Brazil were analyzed. Clinical complexity was defined as the presence of one or more of the following conditions: advanced liver disease (Metavir score F3 or F4 and/or clinical manifestations or ultrasound/endoscopy findings consistent with cirrhosis) or hepatocellular carcinoma and/or 3 or more extrahepatic manifestations and/or comorbidities concomitantly.RESULTS:Among the 1574 patients analyzed, only 41% met the definition of being clinically complex. Cirrhosis or hepatocarcinoma was identified in 22.2% and 1.8% of patients, respectively. According to multiple logistic regression analysis, male sex (p=0.007), age>40 years (p<0.001) and the presence of metabolic syndrome (p=0.008) were independently associated with advanced liver disease.CONCLUSION:The majority of patients did not meet the criteria for admittance to this specialized tertiary service, reinforcing the need to reevaluate public health policies. Enhanced utilization of existing basic and intermediate complexity units for the management of less complex hepatitis C cases could improve care and lower costs.

Improving small-scale wastewater treatment plant performance by using a filtering tertiary treatment unit

The demand for wastewater treatment plants purposed for a single household or groups of households continues to increase as the quality requirements for wastewater treatment become increasingly rigorous. Researchers are constantly searching for new methods to remove phosphorus compounds from wastewater that do not require the use of chemicals.This article describes a newly designed tertiary wastewater treatment unit that increases the effectiveness of the main small-scale (up to 1 m3/d) biological wastewater treatment unit. The tertiary treatment unit is filled with the sorbent material Filtralite P., after the main treatment wastewater flows through the filler without the use of electric power. A compact system consisting of a main (secondary) treatment unit and the newly designed tertiary wastewater treatment unit was tested in accordance with the harmonised European Standard EN 12566-3. During the testing period, no surplus sludge was discharged from the system, no reagents were dosed into it, the system only consumed 119 kW of electric power, and the treated wastewater contained <1 mg/L of phosphorus. The total wastewater treatment efficiency can be explained as follows: COD – 95.2%, BOD5 – 99.2%, SS – 99.4%, NH4-N – 99.6%, Nt – 82.2%, and Pt – 91.8%. The system is efficient, the operational cost is relatively low, it does not use chemical reagents, and it is environment friendly.

Heterogeneous fluidized-bed Fenton process: Factors affecting iron removal and tertiary treatment application

In this research, the factors affecting iron removal were determined for a fluidized-bed Fenton reactor using construction sand as the medium. Most of the particulate iron could be removed by the fluidized-bed Fenton process under optimum conditions. The surface area of the fluidized media available for iron crystallization via heterogeneous nucleation and hydraulic retention time were found to be the key factors controlling the iron removal efficiency. Bed expansion of 50% was sufficient for satisfactory iron removal. Further bed expansion did not provide any significant improvement, and could deteriorate the iron removal performance through scouring effect and increase energy consumption. Formic acid, one of the carboxylic intermediates from organic pollutant oxidation with hydroxyl radicals, remarkably deteriorated the iron removal performance. This is because it not only increased iron solubility through complexation but also hindered heterogeneous nucleation of ferric hydroxide onto the fluidized material. Therefore, in terms of iron removal, the fluidized-bed Fenton process should be applied to treat low-strength wastewater or to serve as a polishing unit to limit the formation of Fe3+-chelating intermediates. As a tertiary treatment unit, the fluidized-bed Fenton reactor could successfully and consistently reduce the COD and color of secondary effluents from pulp and paper mills to below the new and more stringent standards of 120 mg/L and 300 ADMI, respectively. Depending on the water characteristics, total iron removal of 53–81% could be achieved at the optimum retention time.

Sewage treatment effluents in Delhi: A key contributor of β-lactam resistant bacteria and genes to the environment

Rapid emergence of antibiotic resistance (AR) in developing countries is posing a greater health risk and increasing the global disease burden. Lack of access to safe drinking water, poor sanitation and inadequate sewage treatment facilities in these countries are fueling the problem associated with emergence of AR. Rapid proliferation of AR mediated by treated and untreated discharges from sewage treatment plants (STPs) is a prime public health concern. This study aims to understand the occurrence, fate, and routes of proliferation of carbapenem (KPC) and extended spectrum β-lactam (ESBL) resistant bacteria, and selected resistant genes in the samples collected from different unit operations in 12 STPs in New Delhi over two seasons. Strong correlation observed between faecal coliform levels and KPC (R = 0.95, p = 0.005, n = 60) and ESBL (R = 0.94, p = 0.004, n = 60) resistant bacteria levels indicates possible association of resistant bacteria with faecal matter. Different unit operations in STPs proved inefficient in treating resistant bacteria and genes present in the wastewater. However, inclusion of tertiary treatment (chlorination) unit and anaerobic digester in the present STPs resulted in better removal of AR. Significant correlations between antibiotic resistant genes (ARGs) and integron levels indicates a potential for higher rate of AR proliferation in the environment. Microbial culturing indicated the presence of clinically significant drug-resistant pathogens such as Escherichia coli, Pseudomonas putida, Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella pneumoniae, Klebsiella oxytoca, Acinetobacter baumannii, Shigella dysentery and Aeromonas caviae in the STP effluents. The emergence and spread of resistant bacteria through STP effluents poses exposure risk for the residents of the city.

Sources, mechanisms, and fate of steroid estrogens in wastewater treatment plants: a mini review

Steroid estrogens, such as estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethinylestradiol (EE2), are natural and synthetic hormones released into the environment through incomplete sewage discharge. This review focuses on the sources of steroid estrogens in wastewater treatment plants (WWTPs). The mechanisms and fate of steroid estrogens throughout the entire wastewater treatment system are also discussed, and relevant information on regulatory aspects is given. Municipal, pharmaceutical industry, and hospitals are the main sources of steroid estrogens that enter WWTPs. A typical WWTP comprises primary, secondary, and tertiary treatment units. Sorption and biodegradation are the main mechanisms for removal of steroid estrogens from WWTPs. The fate of steroid estrogens in WWTPs depends on the types of wastewater treatment systems. Steroid estrogens in the primary treatment unit are removed by sorption onto primary sludge, followed by sorption onto micro-flocs and biodegradation by microbes in the secondary treatment unit. Tertiary treatment employs nitrification, chlorination, or UV disinfection to improve the quality of the secondary effluent. Activated sludge treatment systems for steroid estrogens exhibit a removal efficiency of up to 100%, which is higher than that of the trickling filter treatment system (up to 75%). Moreover, the removal efficiency of advance treatment systems exceeds 90%. Regulatory aspects related to steroid estrogens are established, especially in the European Union. Japan is the only Asian country that implements a screening program and is actively involved in endocrine disruptor testing and assessment. This review improves our understanding of steroid estrogens in WWTPs, proposes main areas to be improved, and provides current knowledge on steroid estrogens in WWTPs for sustainable development.

A case study for upgrading existing carousel process to achieve low effluent phosphorus discharges

In this study, Al-Qateef wastewater treatment plant was selected as a case representing the upgrade of carrousel technology with tertiary treatment. This technology is applied in many cities in the Eastern province, Kingdom of Saudi Arabia. The use of chemical treatment alternative for phosphorous removal was evaluated versus the newly implemented tertiary treatment unit. The study showed that chemical phosphorous removal has an additional advantage of reducing the final effluent total phosphorus concentration to less than 1 mg/L at an alum dose of 50 mg/L without any significant alteration of the expected final effluent quality that could be achieved by the newly installed sand filters. Furthermore, the study showed that the use of chemical treatment for phosphorous removal could reduce the chlorine dose required for the treated effluent disinfection.