Conventional Activated Sludge Treatment Research Articles

Industrial Wastewater Treatment Using High Rate Activated Sludge and Alum Additive

The high rate activated sludge stage of the multiple-stage sludge treatment plant is characterized by high efficiencies of treatment, cost, and size, compared to conventional activated sludge treatment plants. A pilot plant with an industrial discharge flow of 135L/h was designed according to the highly loaded activated sludge stage (A-stage). The plant simulated the biological and chemical treatment of sludge by adding alum to the aeration tank in dosages of 100, 150, 200 and 250 mg/L. The results clearly indicate that the highly-loaded activated sludge, the A-stage of the absorption/bio-oxidation system, has a high efficiency for the elimination of organic and inorganic matters. Without adding aluminum salt, the chemical oxygen demand, the total phosphate and the total nitrate were approximately 52.43%, 47.82%, and 40.09% respectively. The chemical-biological process with a dosage of 200mg/L alum resulted in 76.07% reduced chemical oxygen demand and improved efficiency of phosphate and nitrate removal to 73.5% and 66.98% respectively compared with the biological process in the A-stage.

Removal of trace organic contaminants by an MBR comprising a mixed culture of bacteria and white-rot fungi

The degradation of 30 trace organic contaminants (TrOC) by a white-rot fungus-augmented membrane bioreactor (MBR) was investigated. The results show that white-rot fungal enzyme (laccase), coupled with a redox mediator (1-hydroxy benzotriazole, HBT), could degrade TrOC that are resistant to bacterial degradation (e.g. diclofenac, triclosan, naproxen and atrazine) but achieved low removal of compounds (e.g. ibuprofen, gemfibrozil and amitriptyline) that are well removed by conventional activated sludge treatment. Overall, the fungus-augmented MBR showed better TrOC removal compared to a system containing conventional activated sludge. The major role of biodegradation in removal by the MBR was noted. Continuous mediator dosing to MBR may potentially enhance its performance, although not as effectively as for mediator-enhanced batch laccase systems. A ToxScreen3 assay revealed no significant increase in the toxicity of the effluent during MBR treatment of the synthetic wastewater comprising TrOC, confirming that no toxic by-products were produced.

Investigation of PPCPs in wastewater treatment plants in Greece: Occurrence, removal and environmental risk assessment

In the present work, an extensive study on the presence of eighteen pharmaceuticals and personal care products (PPCPs) in eight wastewater treatment plants (WWTPs) of Greece has been conducted. The study covered four sampling periods over 1-year, where samples (influents; effluents) from eight WWTPs of various cities in Greece were taken. All WWTPs investigated are equipped with conventional activated sludge treatment. A common pre-concentration step based on SPE was applied, followed by LC–UV/Vis–ESI–MS. Further confirmation of positive findings was accomplished by using LC coupled to a high resolution Orbitrap mass spectrometer. The results showed the occurrence of all target compounds in the wastewater samples with concentrations up to 96.65μg/L. Paracetamol, caffeine, trimethoprim, sulfamethoxazole, carbamazepine, diclofenac and salicylic acid were the dominant compounds, while tolfenamic acid, fenofibrate and simvastatin were the less frequently detected compounds with concentrations in effluents below the LOQ. The removal efficiencies showed that many WWTPs were unable to effectively remove most of the PPCPs investigated. Finally, the study provides an assessment of the environmental risk posed by their presence in wastewaters by means of the risk quotient (RQ). RQs were more than unity for various compounds in the effluents expressing possible threat for the aquatic environment. Triclosan was found to be the most critical compound in terms of contribution and environmental risk, concluding that it should be seriously considered as a candidate for regulatory monitoring and prioritization on a European scale on the basis of realistic PNECs. The results of the extensive monitoring study contributed to a better insight on PPCPs in Greece and their presence in influent and effluent wastewaters. Furthermore, the unequivocal identification of two transformation products of trimethoprim in real wastewaters by using the advantages of the LTQ Orbitrap capabilities provides information that should be taken into consideration in future PPCP monitoring studies in wastewaters.

A comparison between extended aeration sludge and conventional activated sludge treatment for removal of linear alkylbenzene sulfonates (Case study: Kermanshah and Paveh WWTP)

Linear alkylbenzene sulfonates (LASs) are anionic surfactants with extensive application as detergents. Discharge of wastewater containing these chemicals results in negative environmental impacts. In the present study, the process performance of an extended aeration activated sludge (EAAS) system in Paveh’s wastewater treatment plant (WWTP) and a conventional activated sludge (CAS) system in Kermanshah’s WWTP removing LAS and chemical oxygen demand (COD) were compared. The amounts of LAS removal in the CAS and the EAAS systems were calculated as 93.73 and 96.7%, respectively. It was concluded that EAAS system may be used for treating municipal wastewater with better LAS, COD, and total suspended solids (TSS) removal efficiency compared with CAS system.

Pengaruh Penambahan Substrat Organik Pada Limbah Klorinasi Pabrik Kertas Terhadap Pembentukan Gas Methan Dan Penurunan Senyawa Klorin

Kraft mill bleaching process is some significant source of chlorinated organic compounds. In this process, wood pulp is bleached using plant specific sequence of chlorination with chlorine and extraction with alkali. The waste water from chlorination of Kraft bleaching contains many toxic compounds that very difficult to be removed by conventional activated sludge treatment. Adding an organic substrate will affect the methanogenesis. The aims of this study are: (1). To remove adsorbable organichalide (AOX) by anaerobic treatment, (2). Toexamine the effect co-substrates to methanogenesis, such as methanol and glucose, (3). To know the effect of sterilization to decrease of AOX. The result is AOX can be removed anaerobically with or without co-substrate.

The Technology of Biological Nutrient Removal in SBR and the Modifications of the System

Activated sludge, the most common process for treatment of wastewater, has been widely applied in the treatment of domestic sewage, municipal sewage and organic industrial wastewater. Currently, as a number of modifications and refinements have been utilized to improve conventional activated sludge treatment, the process now could be used as a tertiary treatment technique capable of removing both nitrogen- and phosphor-containing compounds in wastewater. Sequencing batch reactor (also known as SBR) method is a novel, revolutionary and promising technique in the field of activated sludge treatment. The automatic control system of SBR employs time as the critical controlling parameter, and thus ensuring a steady and consistent operation for the process. With the increasing applications of computer technology and the automatic (continuous) monitoring devices, the SBR-based process becomes the new spotlight in the industry, while the efforts put into the studies in this field have produced numerous fruitful outcomes.

Removal of 17-β estradiol from wastewater: comparison between a laboratory scale conventional activated sludge and a membrane bioreactor

This work reports the performance of a laboratory scale membrane bioreactor (MBR) and a conventional activated sludge (CAS) treating a real industrial–municipal mixed wastewater, spiked with 17-β estradiol (E2) in micrograms amounts. In order to compare the steady- state conditions of both systems, different sludge retention times (SRT) of 10 and 20 days were applied, while the other operational parameters were maintained unchanged. Results regarding the removal of chemical oxygen demand (COD), nitrogen and E2 have been assessed with statistics analysis using the Mann–Whitney test. MBR outperforms the CAS treatment in terms of COD and nitrogen removal, and the increase in the SRT generally improves the performance of each system. However, E2 was almost completely eliminated in both systems and SRTs applied, leading to removal rates above 99%. Thus, this study shows that the biological elimination of E2 is not directly related to the nitrification rate, and other process or operational parameters should be of importance.

Occurrence and fate of dissolved and particulate antimicrobials in municipal wastewater treatment

Comprehensive study on the occurrence and fate of several classes of antimicrobials, including sulfonamides, trimethoprim, fluoroquinolones and macrolides, in Croatian municipal wastewaters was performed using an integrated approach, which comprised analysis of both dissolved and particulate fractions. A nation-wide screening showed ubiquitous occurrence of human-use antimicrobials in raw wastewater samples with the total concentrations ranging from 2 to 20 μg/L, while veterinary antimicrobials were typically present in much lower concentrations (<100 ng/L). The percentage of the particulate fraction in raw wastewater varied significantly depending on the type of the antimicrobial and the load of suspended solids. A detailed study of the mass flows of dissolved and particulate antimicrobials, performed in the wastewater treatment plant of the city of Zagreb, allowed an improved assessment of the biological and physico-chemical removal mechanisms of investigated compounds during the conventional activated sludge treatment. The overall removal efficiencies of antimicrobials from the water phase were rather variable, ranging from 0% for trimethoprim to 85% for norfloxacin. A significant percentage of fluoroquinolones (norfloxacin and ciprofloxacin) and macrolides (azithromycin and clarithromycin) was associated with the primary and excess secondary sludge, explaining 14–77% of the total removal. The removal, which could be attributed to biological transformation, was relatively poor for all antimicrobials, exceeding 30% only for SMX (32%) and clarithromycin (55%).

Review on the fate of organic micropollutants in wastewater treatment and water reuse with membranes

A brief review of the fate of micropollutants in membrane-based wastewater treatment due to sorption, stripping, biological degradation/transformation and membrane separation is discussed, to give an overview of these technologies due to the growing importance for water reuse purposes. Compared with conventional activated sludge treatment (CAS) micropollutant removal in membrane bioreactor (MBR) is slightly improved due to complete suspended solids removal and increased sludge age. For discharge to sensitive receiving waters advanced treatment, such as post-ozonation or activated carbon adsorption, is recommended. In water reuse plants nanofiltration (NF) and reverse osmosis (RO) efficiently reject micropollutants due to size exclusions as well as electrostatic and hydrophobic effects reaching potable quality. To remove micropollutants fully, additionally post-ozone or the addition of powdered activated carbon (PAC) have to be applied, which in parallel also reduce NDMA precursors. The concentrate has to be treated if disposed to sensitive receiving waters due to its high micropollutant concentration and ecotoxicity potential. The present review summarizes principles and capabilities for the most important membrane-based applications for wastewater treatment, i.e. porous membranes in MBRs (micro- or ultrafiltration) and dense membrane applications (NF and RO) for water reuse.

Removal of sulfonamide antibiotics upon conventional activated sludge and advanced membrane bioreactor treatment

This work reports the removal efficiencies of nine sulfonamides (SAs) and one of their acetylated metabolites during conventional activated sludge (CAS) and membrane bioreactor (MBR) treatments. Two different types of membranes were studied, hollow-fiber membranes and flat-sheet membranes, in two separate pilot plants operating in parallel to a full-scale CAS treatment. A total of 48 water samples and 16 sewage sludge samples were analyzed by liquid chromatography-tandem mass spectrometry. We obtained 100% elimination in the MBR effluents for three SAs (sulfadiazine, sulfadimethoxine, and sulfamethoxypyridazine) and the metabolite. For the rest of the SAs, the removal efficiencies during CAS and MBR treatments were similar and usually below 55%. Sulfamethizole was the most recalcitrant SA, exhibiting negative removal efficiencies in all the treatments investigated. The concentrations of SAs in the different sewage sludge types were also calculated and ranged from 0.01 to 11 ng g(-1). Furthermore, adsorption and biodegradation of SAs in activated sludge were investigated in two sets of batch reactors, which were spiked at high and low concentration (1,000 and 50 ng mL(-1), respectively). All SAs followed a similar trend and, with the exception of sulfathiazole, were not fully eliminated after 25 days of treatment.

The application of UASB-MBR with partial nitrification-denitrification in wastewater reclamation in warm climate

An up-flow anaerobic sludge blanket (UASB) process has been successfully applied for the treatment of municipal wastewaters with methane production for energy recovery. A membrane bioreactor (MBR) was coupled to the UASB to further improve carbon removal. Nitrogen removal was conducted with the UASB-MBR integrated system under optimum conditions which promoted nitrogen removal through a shortcut nitrification-denitrification process. The process achieved 69–86% of soluble chemical oxygen demand (CODsolu) removal and 56–80% of total nitrogen (TN) removal. Biogas production was between 25 and 76 L/m3 wastewater (50–75% methane content) for the treatment of high-strength municipal wastewater. As the anaerobic process combined with a shortcut nitrogen removal step can achieve reduction of footprint, lower greenhouse gas emission and a potential for bioenergy recovery, the integrated UASB-MBR system could be a better choice for municipal wastewater treatment than the conventional activated sludge treatment process in warm climatic conditions.

Enrichment of denitrifying methanotrophic bacteria for application after direct low-temperature anaerobic sewage treatment

Despite many advantages of anaerobic sewage treatment over conventional activated sludge treatment, it has not yet been applied in temperate zones. This is especially because effluent from low-temperature anaerobic treatment contains nitrogen and dissolved methane. The presence of nitrogen and methane offers the opportunity to develop a reactor in which methane is used as electron donor for denitrification. Such a reactor could be used in a new concept for low-temperature anaerobic sewage treatment, consisting of a UASB-digester system, a reactor for denitrification coupled to anaerobic methane oxidation, and a nitritation reactor. In the present study denitrifying methanotrophic bacteria similar to ‘Candidatus Methylomirabilis oxyfera’ were enriched. Maximum volumetric nitrite consumption rates were 33.5mgNO2−-N/Ld (using synthetic medium) and 37.8mgNO2−-N/Ld (using medium containing effluent from a sewage treatment plant), which are similar to the maximum rate reported so far. Though the goal was to increase the rates, in both reactors, after reaching these maximum rates, volumetric nitrite consumption rates decreased in time. Results indicate biomass washout may have significantly decelerated enrichment. Therefore, to obtain higher volumetric consumption rates, further research should focus on systems with complete biomass retention.

Whole effluent toxicity assessment at a wastewater treatment plant upgraded with a full-scale post-ozonation using aquatic key species

Ozonation as final wastewater (WW) polishing step, following conventional activated sludge treatment is increasingly implemented in sewage treatment for contaminant degradation to prevent surface water pollution. While the oxidative degradation of chemicals has been extensively investigated, the in vivo toxicological characteristics of ozonated whole effluents are rarely a matter of research.In the present study, whole effluents were toxicologically evaluated with an in vivo test battery before and after full-scale ozonation and subsequent sand filtration on site at a treatment plant. One aquatic plant (duckweed, Lemna minor) and five invertebrate species of different systematic groups (Lumbriculus variegatus, Chironomus riparius, Potamopyrgus antipodarum, Daphnia magna) were exposed to the effluents in a flow-through-designed test system with a test duration of 7–28d.None of the considered toxicity endpoints correlated with the pollutant elimination. A tendency towards an increased toxicity after ozonation was apparent in three of the test systems showing [statistically] significant adverse effects in the L. variegatus toxicity test (decrease in reproduction and biomass). After sand filtration, adverse effects were reduced to a similar level like after conventional treatment. Solely the Daphnia reproduction test revealed beneficial effects after ozonation in combination with sand filtration.Results of the test battery indicate the formation of adverse oxidation products during WW ozonation. L. variegatus appeared to be the most sensitive of the five test species. Sand filtration effectively removes or detoxifies toxic oxidation products, as toxic effects were subsequently reduced to the level after conventional treatment.

Development and optimisation of an on-line solid phase extraction coupled to ultra-high-performance liquid chromatography–tandem mass spectrometry methodology for the simultaneous determination of endocrine disrupting compounds in wastewater samples

A process using a fully automated on-line solid-phase extraction system combined with ultra-high-performance liquid chromatography and tandem mass spectrometry detection (SPE-UHPLC–MS/MS) has been developed and applied to the determination of 27 endocrine disrupting compounds (EDCs) in sewage samples. This technology allows separation and detection of all substances in a single chromatographic run that requires less than 4min. In order to obtain a more sensitive method for the quantification of these compounds in sewage samples, an on-line solid-phase extraction step with Oasis HLB columns was performed prior to chromatographic determination. The complete analysis of each sample by this process requires only 9min, provides satisfactory recoveries (72–110%) and limits of detection on the order of a few nanograms per liter (0.3–2.1ngL−1), demonstrating their potential for analyses of environmental samples. Thus, this methodology has been applied to samples collected from two wastewater treatment plants (WWTPs) located in Las Palmas de Gran Canaria (Canary Islands, Spain). One of these plants utilised conventional activated sludge treatment (CAS), while the other employed biomembrane reactor treatment (MBR).

Effectiveness of three configurations of membrane bioreactors on the removal of priority and emergent organic compounds from wastewater: comparison with conventional wastewater treatments

In this work the effectiveness of membrane bioreactors as advanced treatment on the removal of emergent and priority organic compounds in wastewater treatment plants has been evaluated during a one-year monitoring study. The studied wastewater treatment plant operates with flat sheet and hollow fibre membranes in two parallel lines. Moreover, a reverse osmosis module connected in series after the hollow fibre membrane was evaluated for one month. Comparison of membrane bioreactor and conventional activated sludge treatment was also investigated, as well as the influence of the physicochemical properties of the compounds on the removal rates achieved. Sixteen pharmaceutical compounds belonging to seven therapeutic groups and eight priority organic pollutants, including linear alkylbenzene sulfonates, nonylphenol and its ethoxylates and phthalate, were monitored. The highest mean concentrations corresponded to priority organic pollutants (309 μg L(-1) of linear alkylbenzene sulfonate C(12)) followed by pharmaceutical compounds (24.5 μg L(-1) of ibuprofen). No significant difference of effectiveness was found among flat sheet and hollow fibre membranes. However, an improvement was obtained with the addition of a reverse osmosis module for most of the compounds. Biodegradation has been shown as the main route involved in the removal of organic compounds during both technologies.

Heat shock protein 47 stress responses in Chinese hamster ovary cells exposed to raw and reclaimed wastewater

As wastewater reclamation and reuse becomes more widespread, risks of exposure to treated wastewater increase. Moreover, an unlimited number of pollutants can be identified in wastewater. Therefore, comprehensive toxicity assessment of treated wastewater is imperative. The objective of this study was to perform a comprehensive toxicity assessment of wastewater treatment systems using stress response bioassays. This powerful tool can comprehensively assess the toxicity of contaminants. In this study, samples from conventional activated sludge treatment, membrane bioreactors (MBRs) with different pore sizes and sludge retention times (SRTs), rapid sand filtration, coagulation, nano-filtration (NF) and reverse osmosis (RO) were investigated. The results of stress response bioassays confirmed that the secondary effluent showed higher stress response than influent indicating that biological treatment generates toxic compounds. The results obtained from molecular weight fractionation of water samples demonstrated that organic matter with a higher molecular weight fraction (>0.1 μm) causes toxicity in secondary effluent. Furthermore, supernatant from MBR reactors showed toxicity regardless of SRT. On the other hand, stress response was not detected in MBR permeates except for an MBR equipped with a larger pore size membrane (0.4 μm) and with a short SRT (12 days). While rapid sand filtration could not remove the toxic compounds found in secondary effluent, coagulation tests, operated at an appropriate pH, were effective for reducing stress response in the secondary effluent. Experimental findings also showed that stress response was not detected in cases of NF and RO permeate subsequent to MBR treatment.

Treatment of soft drink process wastewater by ozonation, ozonation-H2O2 and ozonation-coagulation processes

In this research, we studied the treatment of wastewater from the soft drink process using oxidation with ozone. A scheme composed of sequential ozonation-peroxide, ozonation-coagulation and coagulation-ozonation treatments to reduce the organic matter from the soft drink process was also used. The samples were taken from the conventional activated sludge treatment of the soft drink process, and the experiments using chemical oxidation with ozone were performed in a laboratory using a reactor through a porous plate glass diffuser with air as a feedstock for the generation of ozone. Once the sample was ozonated, the treatments were evaluated by considering the contact time, leading to greater efficiency in removing colour, turbidity and chemical oxygen demand (COD). The effect of ozonation and coagulant coupled with treatment efficiency was assessed under optimal conditions, and substantial colour and turbidity removal were found (90.52% and 93.33%, respectively). This was accompanied by a 16.78% reduction in COD (initial COD was 3410 mg/L). The absorbance spectra of the oxidised products were compared using UV-VIS spectroscopy to indicate the level of oxidation of the wastewater. We also determined the kinetics of decolouration and the removal of turbidity with the best treatment. The same treatment was applied to the sample taken from the final effluent of the activated sludge system, and a COD removal efficiency of 100% during the first minute of the reaction with ozone was achieved. As a general conclusion, we believe that the coagulant polyaluminum chloride - ozone (PAC- ozone) treatment of wastewater from the manufacturing of soft drinks is the most efficient for removing turbidity and colour and represents an advantageous option to remove these contaminants because their removal was performed in minutes compared to the duration of traditional physical, chemical and biological processes that require hours or days.

Fate and removal of permethrin by conventional activated sludge treatment

The fate and removal of permethrin during conventional wastewater treatment were evaluated at pilot‐plant scale at different concentrations of mixed liquor suspended solids (MLSS) and, hence, different solids retention times (SRT). At feed concentrations of 0.26–0.86 µg L−1, the permethrin was removed by primary treatment at an efficiency rate of 37%, similar to previously reported data, and from 40% to 83% for secondary treatment, decreasing with decreasing SRT. Comparable ranges, from 37% up to 98%, have been reported for micropollutants with similar physicochemical properties to permethrin, such as galaxolide and tonalide. Little difference in removal was noted between the medium and low MLSS concentrations trials, the main difference in treated effluent permethrin concentration arising on changing from high to medium MLSS levels. This was attributed to the limited acclimatization period employed in these two trials, leading to higher levels of soluble organic matter in the treated water, with which the permethrin appeared to be associated.

Determination of various estradiol mimicking-compounds in sewage sludge by the combination of microwave-assisted extraction and LC–MS/MS

In this work, we present the development and application of a microwave assisted extraction followed by liquid chromatography–tandem mass spectrometry methodology (MAE-LC–MS/MS) for the determination of various estradiol-mimicking compounds in sewage sludge samples. For the purification of the MAE extracts, we have employed a solid phase extraction (SPE) clean-up procedure, previously optimised. The entire method provides recoveries between 71.7% and 103.1%, with relative standard deviation lower than 11.1% and limits of detection ranging from 0.6 to 3.5ngg−1. The developed method was applied to samples from three wastewater treatment plants (WWTPs) located in Las Palmas of Gran Canaria (Spain), two of which had a conventional activated sludge treatment (AST), whereas the third treatment plant had an advanced membrane bioreactor treatment (MBR). All of the analytes in the study, including (nonylphenol (NP), octylphenol (OP), and some of their ethoxylated chains APnEOs (n≤7), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE) and bisphenol-A (BPA)), were found in almost all samples in concentrations ranging from 0.9 to 710.2ngg−1.

Ozonation and activated carbon treatment of sewage effluents: Removal of endocrine activity and cytotoxicity

Concerns about endocrine disrupting compounds in sewage treatment plant (STP) effluents give rise to the implementation of advanced treatment steps for the elimination of trace organic contaminants. The present study investigated the effects of ozonation (O3) and activated carbon treatment (AC) on endocrine activities [estrogenicity, anti-estrogenicity, androgenicity, anti-androgenicity, aryl-hydrocarbon receptor (AhR) agonistic activity] with yeast-based bioassays. To evaluate the removal of non-specific toxicity, a cytotoxicity assay using a rat cell line was applied. Wastewater (WW) was sampled at two STPs after conventional activated sludge treatment following the secondary clarifier (SC) and after subsequent advanced treatments: O3, O3 + sand filtration (O3-SF), and AC. Conventional treatment reduced estrogenicity, androgenicity, and AhR agonistic activity by 78–99% compared to the untreated influent WW. Anti-androgenicity and anti-estrogenicity were not detectable in the influent but appeared in SC, possibly due to the more effective removal of respective agonists during conventional treatment. Endocrine activities after SC ranged from 2.0 to 2.8 ng/L estradiol equivalents (estrogenicity), from 4 to 22 μg/L 4-hydroxytamoxifen equivalents (anti-estrogenicity), from 1.9 to 2.0 ng/L testosterone equivalents (androgenicity), from 302 to 614 μg/L flutamide equivalents (anti-androgenicity), and from 387 to 741 ng/L β-naphthoflavone equivalents (AhR agonistic activity). In particular, estrogenicity and anti-androgenicity occurred in environmentally relevant concentrations. O3 and AC further reduced endocrine activities effectively (estrogenicity: 77–99%, anti-androgenicity: 63–96%, AhR agonistic activity: 79–82%). The cytotoxicity assay exhibited a 32% removal of non-specific toxicity after O3 compared to SC. O3 and sand filtration reduced cytotoxic effects by 49%, indicating that sand filtration contributes to the removal of toxicants. AC was the most effective technology for cytotoxicity removal (61%). Sample evaporation reduced cytotoxic effects by 52 (AC) to 73% (O3), demonstrating that volatile substances contribute considerably to toxic effects, particularly after O3. These results confirm an effective removal or transformation of toxicants with receptor-mediated mode of action and non-specific toxicants during O3 and AC. However, due to the limited extractability, polar ozonation by-products were neglected for toxicity analysis, and hence non-specific toxicity after O3 is underestimated.