Secondary Biological Treatment Research Articles

Oxidation of sulfides following anaerobic municipal wastewater treatment for non-potable reuse applications

Anaerobic secondary biological wastewater treatment could increase energy efficiency by avoiding energy-intensive aeration while producing methane that could be harvested for energy production.

The photocatalyst with a strong internal electric field grown in situ on the surface of copper foam collaborates with peroxymonosulfate to enhance directional charge transfer and achieve ultra-fast Mn+/M(n+1)+ cycling

To address three pressing problems that limit the application of photocatalytic synergic peroxymonosulfate (PMS) technology, namely difficult reuse, low photogenerated carrier separation efficiency, and sluggish metallic ions redox cycle, we utilized an in-situ growth method to construct a vertical nanosheet heterojunction on the surface of copper foam (CF). This heterojunction is characterized by a strong internal electric field (IEF) that serves as both a “pump” for the rapid and efficient migration of electrons and a driving force for the activation of PMS by these electrons. In the CF@CCS@CO-3/7/Vis/PMS system, the photoelectrons generated by photocatalysis quickly replenish the high valence metals activated by PMS, allowing for highly efficient cycling of differently valenced metal ions and reducing the dissolution of high valence metal ions produced by PMS. As a result, close to 100 % of ciprofloxacin (CIP) was degraded within 60 min in the CF@CCS@CO-3/7/Vis/PMS system with a reaction rate constant k of 0.0621 min−1, which is about 3.22 times higher than that of the CF@CCS@CO-3/7/Vis system and 2.65 times higher than that of the CF@CCS@CO-3/7/PMS system. Moreover, the in-situ growth of active ingredients with vertical nanosheet structure on the CF surface can well maintain structure and reactivity in complex environments, allowing more than 10 cycles to be realized. The results of the free radical burst assay and EPR analysis indicated that SO4∙−, ∙O2− and h+ were the main reactive species involved in the catalytic process. Building upon CF@CCS@CO-3/7, we assembled a fixed-bed continuous treatment device that enables high mineralization flow treatment of pharmaceutical wastewater (after Secondary biological treatment).

Developments and expansions of a suite of trickling filters models

AbstractIn the United Kingdom, trickling filters remain the most widespread secondary biological treatment process for municipal sewage treatment in terms of number of installations. Ongoing improvement in environmental quality of surface waters requires many of these sites to meet stringent effluent standards. Since publication of the original model for nitrification on mineral media trickling filters by Pearce and Williams in 1999 and the model for nitrification on plastic media filters by Pearce and Edwards in 2010, they have attracted widespread use. Since publication, the models have undergone some refinement and benefitted from an increased application range. Furthermore, recent publications by Pearce and Yang have delivered widely based models for predicting average and seasonal humus tank effluent suspended solids and variability at a resolution of daily 95th percentile performance. This paper presents recent developments of the nitrification models and consolidates the suite of models now available for trickling filter design, evaluation and operation.

Life cycle energy use and greenhouse gas emissions for a novel algal-osmosis membrane system versus conventional advanced potable water reuse processes: Part I

This study applied a life cycle assessment (LCA) methodology for a comparative environmental analysis between an innovative algae resource recovery and near zero-liquid discharge potable reuse system (i.e., the main system) versus a conventional potable reuse system (i.e., the benchmark system) through energy use and greenhouse gas (GHG) emissions. The objective of this study is to demonstrate that pilot-scale data coupled with LCA would provide valuable information for system optimization, integration, and improvements for the design of environmentally sustainable full-scale systems. This study also provides decision-makers valuable information regarding the energy demand and environmental impact of this innovative main system compared to a typical tried-and-true system for potable water reuse. The main system consists of a novel algal-based wastewater treatment coupled with a dual forward osmosis and seawater reverse osmosis (Algal FO-SWRO) membranes system for potable water recovery and hydrothermal liquefaction (HTL) to recover biofuels and valuable nutrients from the harvested algal biomass. The benchmark system refers to the current industry standard technologies for potable water reuse and waste management including a secondary biological treatment, microfiltration (MF), brackish water reverse osmosis (BWRO), ultraviolet/advanced oxidation process (UV-AOP), and granular activated carbon (GAC), as well as anaerobic digestion for sludge treatment. Respective energy and GHG emissions of both systems were normalized and compared considering 1 m3 of water recovered. Based on an overall water recovery of 76% designed for the benchmark system, the energy consumption totaled 4.83 kWh/m3, and the system was estimated to generate 2.42 kg of CO2 equivalent/m3 with most of the emissions coming from the biological treatment. The main system, based on an overall water recovery of 88%, was estimated to consume 4.76 kWh/m3 and emit 1.49 kg of CO2 eq/m3. The main system has high environmental resilience and can recover bioenergy and nutrients from wastewater with zero waste disposal. With the application of energy recovery devices for the HTL and the SWRO, increase in water recovery of the FO membrane, and replacement of the SWRO membrane with BWRO, the main system provides an energy-competitive and environmentally positive alternative with an energy demand of 2.57 kWh/m3 and low GHG emissions of 0.94 kg CO2 eq/m3.

In vitro bioanalytical assessment of the occurrence and removal of bioactive chemicals in municipal wastewater treatment plants in Korea

Effluents of wastewater treatment plants (WWTPs) contain various organic micropollutants, some of which can exert negative effects on the quality of receiving waters or drinking water sources. This study monitored two full-scale WWTPs in Korea for the occurrence and removal of bioactive chemicals for a one-year period using a battery of in vitro bioassays as a complementary approach to chemical analysis. Bioassays covering different endpoints were employed, such as hormone receptor activation (AR and ERα), xenobiotic metabolism (PAH and PXR), oxidative stress response (Nrf2), and cytotoxicity. The WWTP influents showed AR, ERα, and PAH activities at ng/L - μg/L and PXR and Nrf2 activities at μg/L - mg/L as bioanalytical equivalent concentrations of a reference compound for each bioassay. These bioactivities decreased along with the WWTP treatment train, with significant removals achieved by the secondary biological treatment processes. Cytotoxicity was observed only for some municipal wastewater (M-WWTP) influents but was below the limit of quantification for most cases. The influent and effluent bioactivities observed in this study were mostly comparable to those reported in other WWTPs in the literature. Comparison of the bioactivities with the effect-based trigger (EBT) values indicates that the impact of WWTP effluents on receiving water quality was low for most endpoints. For Nrf2, however, further investigation is required to evaluate the observed high bioactivities compared with the current EBT. The observed ERα activity could partly be explained by the presence of some steroid estrogens. Overall, our results contribute to an important database for the concentrations and removal efficiencies of bioactive chemicals in WWTPs and demonstrate bioassays as a useful tool for urban water quality monitoring.

The application of bioremediation in wastewater treatment plants for microplastics removal: a practical perspective.

Wastewater treatment plants (WWTPs) play the role of intercepting microplastics in the environment and provide a platform for bioremediation to remove microplastics. Despite, this opportunity has not been adequately studied. This paper shows the potential ways microplastics-targeted bioremediation could be incorporated into wastewater treatment through the review of relevant literature on bioaugmentation of watertreatment processes for pollutants removal. Having reviewed more than 90 papers in this area, it highlights that bioremediation in WWTPs can be employed through bioaugmentation of secondary biological treatment systems, particularly the aerobic conventional activated sludge, sequencing batch reactor, membrane bioreactor and rotating biological contactor. The efficiency of microplastics removal, however, is influenced by the types and forms of microorganisms used, the polymer types and the incubation time (100% for polycaprolactone with Streptomyces thermoviolaceus and 0.76% for low-density polyethylene with Acinetobacter iwoffii). Bioaugmentation of anaerobic system, though possible, is constrained by comparatively less anaerobic microplastics-degrading microorganisms identified. In tertiary system, bioremediation through biological activated carbon and biological aerated filter can be accomplished and enzymatic membrane reactor can be added to the system for deployment of biocatalysts. During sludge treatment, bioaugmentation and addition of enzymes to composting and anaerobic digestion are potential ways to enhance microplastics breakdown. Limitations of bioremediation in wastewater treatment include longer degradation time of microplastics, incomplete biodegradation, variable efficiency, specific microbial activities and uncertainty in colonization. This paper provides important insight into the practical applications of bioremediation in wastewater treatment for microplastics removal.

Establishing log reduction values for wastewater treatment processes from ambient influent and effluent pathogen monitoring data

In developing wastewater treatment regulations and guidelines for potable reuse, the reduction of pathogens is of critical importance. In draft regulations, the state of California has proposed overall treatment process log reduction values (LRVs) of 20, 14, and 15 respectively for viruses, Giardia cysts, and Cryptosporidium oocysts, for direct potable reuse. In meeting the log reduction requirements, agencies have sought to obtain credit for LRVs achieved consistently through secondary biological and tertiary wastewater treatment, in addition to the LRVs achieved through advanced water treatment. The purpose of this paper is to illustrate how to determine pathogen LRVs, using ambient wastewater treatment pathogen monitoring data and the rank-paired covariant method of analysis.

Pathogen reduction by ozone-biological activated carbon-based advanced water reclamation for reuse.

Ozone-biological activated carbon (ozone-BAC)-based technologies are emerging as an appealing option for potable reuse systems; however, uncertainty remains regarding the reduction of waterborne pathogens. Common log reduction requirements have been modeled after California Department of Drinking Water's 12-10-10 log reduction value (LRV) for enteric virus, Cryptosporidium, and Giardia, respectively. The objective of this research was to investigate appropriate LRVs of pathogens that can be achieved in ozone-BAC-based treatment systems and to assess the applicability of employing drinking water pathogen guidelines for potable reuse applications. A pilot scale ozone-BAC-based treatment train was operated at two water reclamation facilities in Reno, Nevada, USA. Virus, Cryptosporidium, Giardia, and bacterial indicators were monitored across individual and combined treatment processes. Pathogen barriers investigated include conventional filtration, ozonation, and ultraviolet disinfection. Based on sampling and treatment validation strategies, the three pathogen barriers can provide minimum LRVs of 13-9-9.5 for virus, Giardia, and Cryptosporidium. Secondary biological treatment can provide additional pathogen LRVs with site-specific sampling. The present study addresses regulatory uncertainties associated with ozone-BAC pathogen reduction. PRACTITIONER POINTS: Ozone-biological activated carbon-based advanced treatment can meet pathogen LRV requirements with a minimum of three pathogen barriers. Successfully applied drinking water pathogen reduction guidelines for potable reuse applications verified by operational criteria. Low presence of pathogens requires surrogates and indicator analyses and variety of monitoring techniques to verify pathogen log reduction.

Wastewater substrate disinfection for cyanobacteria cultivation as tertiary treatment.

Cultivation of microalgae or/and cyanobacteria in nutrient-rich wastewaters offers an opportunity for enhancing sustainability of tertiary wastewater treatment processes via resources/energy recovery/production, mitigation of emitted GHGs and provision of added value products. However, maintaining a monoculture in wastewater-media constitutes a significant challenge to be addressed. In this regard, the present work assesses the efficiency of the low-cost wastewater substrate disinfection techniques of filtration, use of NaClO, H2O2 or Fe(VI), as a preliminary treatment stage upstream a cyanobacteria cultivation photobioreactor. The growth rate of cyanobacterium Synechococcus elongatus PCC 7942, and nitrate and phosphate removal rates, were experimentally assessed in cultivation setups with biologically treated dairy wastewater that had been subjected to a single or a synergetic couple of disinfection techniques. The results showed that filter thickness has a greater effect on disinfection efficiency than filter pore size. Furthermore, the disinfection efficiency of Fe(VI), which was produced on-site by electrosynthesis via a Fe0/Fe0 cell, was greater than that of NaClO and H2O2. Filtration at ≤ 1.2-μm pore size coupled with chemical disinfection led to unhindered Synechococcus elongatus PCC 7942 growth and efficient nitrate and phosphate removal rates, at dosages, in terms of Concentreation-Time (CT) product,of CT ≥ 270mgmin L-1 for NaClO and CT ≥ 157mgmin L-1 for Fe(VI). The coagulation action of Fe(III) species that result from Fe(VI) reduction and the oxidation action of Fe(VI) can assist in turbidity, organic compounds and phosphorous removal from wastewater media. Moreover, the residual iron species can assist in Synechococcus elongatus PCC 7942 harvesting and may enhance photosynthesis rate by increasing light transfer efficiency. Thus, a filtration configuration coupled with chemical disinfection, preferably using ferrates, downstream of sedimentation tank of a secondary biological wastewater treatment stage is proposed as a necessary, efficient and low-cost disinfection technique for full-scale scale implementation of cyanobacteria cultivation as tertiary wastewater processes.

Psychrophilic treatment of municipal wastewater with a combined UASB/ASD system, and perspectives for improving urban WWTP sustainability

According to new paradigms of urban wastewater management, energy savings and resources and energy recovery from sewage will assume an ever-increasing importance. Anaerobic processes, aside from being more energy efficient than conventional aerobic ones, are particularly suited to recover embedded organic energy, improving the overall energy balance of treatment processes, however, their performance is limited by low temperatures and slower kinetics. In this study, a pilot Upflow Anaerobic Sludge Blanket (UASB) reactor was operated to treat municipal wastewater at low temperature regime (16.5–18.5 °C) for 22 weeks, both as standalone process and combined with a sidestream anaerobic sludge digester. Process performance highlighted good system robustness, as proved by stable pH and volatile fatty acid/total alkaline buffer capacity ratio, even though observed methane yield was low. Observed COD and TSS removal efficiencies were in the ranges of 60–69% and 63–73%, respectively. Methane production ranged between 0.106 and 0.132 Nm3CH4/kgCODrem. An economic assessment was carried out to evaluate the feasibility and benefits of implementing UASB pre-treatment of municipal wastewater in existing conventional facilities (activated sludge and anaerobic sludge digestion), showing that significant energy demand reduction could be achieved for both biological secondary treatment and sludge management, leading to considerable operational economies, and possible positive economic returns within a short pay-back period (3–4 yrs).

Variation of mercury fractionation and speciation in municipal sewage treatment plant: effects of mercury on the atmosphere.

The speciation of mercury in various processing units of sewage treatment in autumn and winter were studied to understand the conversion and fate of mercury. The results show that the average concentrations of total mercury (THg) in the influent were 130.5 ± 69.8ng/L and 231.3 ± 107.2ng/L in autumn and winter, respectively, and the particulate mercury was the main speciation (accounting for 59.3% and 86.9%, respectively). The proportion of dissolved mercury increased after treatment, and the total removal efficiencies of THg were 78.9% and 90.8%, respectively. The release of mercury into the atmosphere during wastewater treatment was studied for the first time. The dissolved gaseous mercury levels in the influent in autumn and winter were 0.60 ± 0.40ng/L and 0.34 ± 0.21ng/L, respectively. The average gaseous element mercury concentration in aerobic tank air was 6.34 ± 0.49ng/m3. The estimated mercury from aeration was 6.4kg per year in China. The dissolved gaseous mercury will be released to the air if the sewage treatment plant is open-air. Closed sewage treatment and collection of waste gas treatment can reduce the influence of released mercury. Mercury releases into the atmosphere in the process of sewage treatment are one of the fates of mercury in sewage. Closed sewage treatment and collection of waste gas treatment are necessary to reduce the influence of released mercury. The reactive mercury levels in the influents of autumn and winter were 1.28 ± 0.49ng/L and 1.96 ± 0.43ng/L, and these levels account for a small proportion of THg, only 1.7% and 0.8%. Hg2+ were released by the degradation of organic matter in the secondary biological treatment. The THg levels in dehydrated sludge were higher than those in biochemical sludge but lower than the maximum limit of THg in agricultural sludge.

Occurrence and fate of poly- and perfluoroalkyl substances (PFAS) in urban waters of New Zealand

Information on the occurrence of PFAS in aquatic matrices of countries with no PFAS manufacturing, e.g., New Zealand, is limited. Also, the fingerprint of PFAS along an urban water cycle, following water path from wastewater treatment plant (WWTP) effluent to treated drinking water has not been widely assessed. Hence, 38 long-, short-, ultrashort-chain PFAS and fluorinated alternatives (including precursors) were monitored in this study by collecting composite samples from two urban WWTPs of New Zealand and grab samples from the water bodies receiving the WWTPs’ effluents and a drinking water treatment plant, whose source water received the effluent of one of the studied WWTPs. ∑PFAS at concentrations 0.1 – 13 ng/L were detected in all wastewater samples, including influents and different treatment stages of the two WWTPs (WW1 and WW2). The fate of most PFAS was similar in the two WWTPs, despite large differences in WWTPs’ PFAS loads in the influents, serving populations (1.6 vs 0.16 million), total capacities (300 vs 54 million liters per day), and designs (aerobic and anoxic secondary treatment vs aerobic only). The fate of PFAS in WWTPs appeared to be driven by a range of processes. For instance, a simultaneous increase (41.6%) in short-chain perfluorohexanoic acid (PFHxA) concentrations and decrease (49.7%) in precursor 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations after secondary biological treatment suggested possible transformation of 6:2 FTS into PFHxA during the treatment. In contrast, the reason behind an average decrease of 35% in ultrashort-chain perfluoropropionic acid (PFPrA) concentrations after treatment was unclear, and further studies are recommended. The concentrations of a linear isomer of long-chain perfluorosulfonic acid (PFOS-L) decreased (48%) in the effluent, possibly due to its partitioning to sludge. Although the concentrations of PFAS in coastal waters suggested that the WW1 effluent is a potential source of PFAS, earlier dispersion model and no detection of PFAS in the receiving waters of WW2 implied that other sources, such as septic systems, peripheral industries, and the airport, could also be contributing to PFAS in coastal waters. The source of ultrashort-chain PFPrA (5.5 ng/L) detected in the treated drinking water produced from that river was unclear. The monitoring results confirm incomplete removal of PFAS in WWTPs, indicate a possible transformation of unknown precursors present in wastewater into short-chain perfluoroalkylcarboxylic acids (PFCAs) during biological treatment, and reveal a possible accumulation of perfluoroalkylsulfonic acids (PFSAs) in the sludge, overall suggesting the circulation of PFAS in urban water systems.

Reduction of Colour from effluents of Pulp and Paper Industry by Ozonation: A Review

Pulp and paper making is the major old process industry in India which is water intensive and generates heavy water pollution. Pulp and paper industries are the fifth largest contributor to industrial water pollution. Waste water is generated from each and every section of paper making process and depends upon the type of pulping and bleaching process. Presently, primary and secondary (Biological) treatment systems based on activated sludge process are widely used by paper industry for effluent treatment. The process requires high energy and chemical inputs and involves high operational costs. One of the novel processes for treating effluent is its oxidation through ozonation which is a greener way of degrading pollutants. Ozonation of intermediate stage effluents having high colour load is more effective for industrial application and re-utilization.

Removal efficiency of organic micropollutants in successive wastewater treatment steps in a full-scale wastewater treatment plant: Bench-scale application of tertiary treatment processes to improve removal of organic micropollutants persisting after secondary treatment

The goal of this study was to investigate the occurrence and removal of 52 organic micropollutants (OMPs) during each wastewater treatment step in a full-scale wastewater treatment plant (WWTP). Pharmaceuticals such as metformin, acetaminophen, caffeine, ibuprofen, cimetidine and naproxen were found with high average concentrations in the influent. Most OMPs were not affected by the primary treatment (removal <10%), while secondary biological treatment contributed the most to overall removal of the OMPs. Among the three lanes of the secondary treatment of the WWTP, a combined anaerobic-anoxic-oxic process followed by a membrane bioreactor (A2O–MBR) process effectively facilitated removal of the OMPs (96%) using a different redox: a conventional activated sludge (CAS) process exhibited removal of approximately 85% of total concentrations of the OMPs, while a Modified Ludzack-Ettinger (MLE) process achieved approximately 92.1% removal. Removal of more than 50% of the concentrations of 13 targeted OMPs was observed in the secondary effluent (except for metformin showing only 3.8% removal) via adsorption with powdered activated carbon (PAC) as additional tertiary treatment. Metformin, inadequately removed by additional tertiary treatments, was effectively removed by a biological activated carbon (BAC) process, reaching a removal efficiency of 90.5%. To increase the removal of the amounts and types of OMPs with various physico-chemical properties, hybrid processes through a combination of diverse advanced treatment should be tailored to WWTPs.

Protozoa reduction through secondary wastewater treatment in two water reclamation facilities

The State of Nevada, USA Administrative Code requires a 12-log enteric virus reduction/inactivation, 10-log Giardia cyst reduction, and 10-log Cryptosporidium oocyst reduction for Category A+ reclaimed water suitable for indirect potable reuse (IPR) based on raw wastewater to potable reuse water. Accurately demonstrating log10 reduction values (LRVs) through secondary biological treatment prior to an advanced water treatment train enables redundancy and resiliency for IPR projects while maintaining a high level of public confidence. LRVs for Cryptosporidium and Giardia resulting from secondary biological treatment are not fully established due to a wide range of performance variabilities resulting from different types of secondary biological treatment processes employed in water reclamation. A one-year investigation of two full-scale northern Nevada (e.g. ≤4 mgd; 1.5 × 107 L/day) water reclamation facilities (WRFs) was conducted to monitor Cryptosporidium oocysts and Giardia cysts in untreated wastewater and secondary effluent. This study aimed at establishing secondary treatment LRVs, monitor WRF performance and attempted to correlate performance to protozoan reduction. California's IPR regulations, in which Nevada IPR regulations were modeled after, were based on a maximum concentration of 5-logs (cysts/L) of Giardia and 4-logs (oocysts/L) of Cryptosporidium. The recovery-corrected Giardia and Cryptosporidium concentrations measured in untreated influent (20 samples each at each WRF) were below 5-log cysts/L at the 99th percentile (maximum 4.4-log cysts/L) and 4-log oocysts/L (maximum 2.7 log oocysts/L), respectively. Both secondary treatment WRFs produced secondary effluent that is consistently better than federal and the State of Nevada requirements and perform within an operating envelop for other secondary facilities. Given the results, it appears that a minimum conservative estimate for LRVs for well-operated secondary activated sludge treatment plants (at the 5th percentile) of 0.5 LRV credit for Cryptosporidium and 2.0 LRV for Giardia is warranted. These minimum LRVs are consistent with a conservative review of the available literature.

Fouling and mitigation mechanisms during direct microfiltration and ultrafiltration of primary wastewater

Direct membrane filtration (DMF) has recently gained attention as an alternative secondary biological wastewater treatment process. This study evaluated direct microfiltration (MF) and ultrafiltration (UF) performance and cleaning protocols during crossflow DMF of primary municipal wastewater effluent. Several types of MF and UF membranes were examined by threshold flux determination, and two types of membranes (MF, 0.08 μm; UF, 100 kDa) were chosen for exploring membrane fouling mechanisms at different feed pressures via both fouling resistance analysis and optical coherence tomography (OCT) observation. The results revealed that both MF and UF displayed three-stage fouling behaviors, i.e., initial intermediate pore blocking followed by two-stage cake filtration. Increasing feed pressure from 8 kPa to 50 kPa could accelerate physically reversible fouling rate (consistent with simulated cake filtration constant). During physical flushing, the cake layer was more readily removed from the UF membrane; while residual porous cake layer was present on the MF membrane, regardless of the feed pressure. With extending filtration-cleaning cycle, shortening filtration duration and elevating cleaning solution temperature to from 25 °C to 50 °C benefited for irreversible fouling alleviation. At 50 °C, the geothermal water performed similar cleaning behaviors as clean water, facilitating lower reversible and irreversible fouling than the geothermal brine. This study shed light on the feasibility of using high temperature geothermal water for periodic physical cleaning during DMF of wastewater under Icelandic scenario.

Effect of membrane filtration on the fate of polychlorinated biphenyls in wastewater treatment

The Spokane River is impacted by levels of polychlorinated biphenyls (PCBs) that have triggered fish consumption advisories and exceed water quality standards. Select wastewater treatment plants (WWTPs) on the river have been upgraded from secondary (biological) treatment to tertiary treatment in the form of membrane filtration to address phosphorus contamination. Because membrane filtration is effective at removing particles, it is likely to reduce PCB concentrations in the effluent as well. In this work, PCBs measured in the influents and effluent of several WWTPs discharging to the river were examined. Implementation of membrane filtration reduced PCB concentrations in the effluent (and therefore PCB loads to the river) by 33% at a facility that produces recycled and virgin paper and by ∼55% at municipal WWTPs, compared to secondary (activated sludge) treatment. Largest reductions in concentrations in effluent and loads were achieved for higher molecular weight (MW) PCB congeners (i.e. those with six or more chlorines), homologs, and formulations. The more modest reductions in effluent concentrations achieved at the paper WWTP may be due to the mix of PCBs in the wastewater there: it contained primarily the low MW Aroclor 1242 (presumably from carbonless copy paper) and PCB 11 (3,3′-dichlorobiphenyl) possibly from pigments. PCBs that appear to be associated with silicone products such as caulk, tubing, and o-rings are relatively more abundant in the effluent of some plants compared to the influent, suggesting that these congeners arise from contamination during sampling or from within the plant itself. At some WWTPs, this contamination accounts for nearly a third of PCBs measured in the effluent.

Identification and removal of sulfhydryl groups from wastewaters

Thiols represent a source of environmental pollution especially wastewater. This work proposed to study the elaboration of cellulose acetate polymer-based membranes for their application in the removal of a sulfhydryl groups of real biological treated wastewaters. The addition of nanoparticles to membranes improves the water purification capacity by promoting a good separation of sulfur, more particularly by ZnO-NPs. We used ultrafiltration membrane-assisted ZnO and TiO2 NPs application on real effluents from different biological treatment plants. We identified the hydrosulfite (thiol) group in wastewater and we used membrane processes ultrafiltration technique for sulfur removal. We evaluated the degradation of sulfur in biological treatment plants in Tunisia: The urban wastewater treatment plant or the conventional plant of Rades Malienne is a secondary biological wastewater treatment plant noted STEP1. The rural wastewater treatment plant based vertical flow planted with Phragmites australis from the Grombalia region noted STEP2 and rural wastewater treatment plant based horizontal flow planted with Phragmites australis from the Grombalia region noted STEP3. STEP1 is found to be more loaded with sulfur. Application of AC-ZnO membrane gives 99.07% and 99.55% of sulfur removal from wastewater of STEP1 and STEP3. STEP3 is 50 times less charged on sulfur than STEP1. We suggested that when the sulfur content is high, this leads to an increase in mineral elements. This could be explained by the interactions between thiols and the major elements that cause mineral pollution.

Molecular insight into the variation of dissolved organic phosphorus in a wastewater treatment plant

To date, eutrophication becomes a great concern of vulnerable aquatic systems. Dissolved organic phosphorus (DOP) discharged from wastewater treatment plant (WWTP) holds a large source of phosphorus in receiving water. However, due to the complexity of DOP, their variation and fate in WWTP remain unknown at the molecular level, and are always overlooked. Here, the variation of DOP in a WWTP was uncovered via Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Results show that 95% of DOP in the influent could be removed by the secondary biological treatment processes. The removed DOP species were mainly lipids with the molecular characteristics of low oxygen content, low unsaturation and low aromaticity. Meanwhile, during biological treatments, some new DOP species, especially lignin/carboxylic rich alicyclic molecules (CRAM) that possessed high oxygen content, high unsaturation and high aromaticity, were produced and released into the secondary effluent. In the subsequent tertiary treatment, coagulation by aluminum salt tended to remove high molecular weight and high oxygen content DOP species in the secondary effluent, which was complementary to the biological treatment. However, the sand filter usually retained microorganisms, which would result in the generation of new DOP species in this process. During the final ultraviolet disinfection process, DOP was effectively mineralized to phosphate, especially the species with high molecular weight and highly unsaturated aromatic DOP species (e.g., lignin/CRAM and tannin), which had higher UV absorbance. The revealed variation of DOP in WWTP is beneficial to optimize the treatment processes to enhance the removal of DOP.

Hybrid zeolite-based ion-exchange and sulfur oxidizing denitrification for advanced slaughterhouse wastewater treatment

The discharge of slaughterhouse wastewater (SWW) is increasing and its wastewater has to be treated thoroughly to avoid the eutrophication. The hybrid zeolite-based ion-exchange and sulfur autotrophic denitrification (IX-AD) process was developed to advanced treat SWW after traditional secondary biological process. Compared with traditional sulfur oxidizing denitrification (SOD), this study found that IX-AD column showed: (1) stronger ability to resist NO3- pollution load, (2) lower SO42- productivity, and (3) higher microbial diversity and richness. Liaoning zeolites addition guaranteed not only the standard discharge of NH4+-N, but also the denitrification performance and effluent TN. Especially, when the ahead secondary biological treatment process run at the ultra-high load, NO3--N removal efficiency for IX-AD column was still ~100%, whereas only 64.2% for control SOD column. The corresponding average effluent TN concentrations for IX-AD and SOD columns were 5.89 and 65.55mg/L, respectively. Therefore, IX-AD is a promising technology for advanced SWW treatment and should be widely researched and popularized.