Energy recovery by anaerobic digestion of algal biomass from integrated microalgae/constructed wetland wastewater treatment.

The present study evaluated the potential for biogas generation from microalgae (MA) biomass and macrophytes used in vertical flow constructed wetlands (VFCW). The samples were obtained by separation and collection of MA after a hydraulic retention time of 14 days, frozen and taken to the laboratory, while the macrophytes of VFCW were obtained, by pruning, every 6 months. The obtained results presented reductions of 63.22% and 61.18% for COD and BOD5, respectively, and removal efficiencies of 53.91% for TP and 99.98% de N-NH3. Average biogas generation was 2322.51 NmL-gSV-1 with 54.61% CH4 (winter/2019), 4491.47 Nml-gSV-1 with 57.17% CH4 (spring/2019), 680.78 NmL-gSV-1 with 16.04% CH4 (summer/2020), and 681.0 NmL-gSV-1 with 19.86% CH4 (autumn/2020) for MA biomass and generation of biogas of 3826.70 NmL-gSV-1 with 44.26% CH4 for VFCW biomass in winter and spring/2019 and of 829.68 NmL-gSV-1 with 17.06% CH4 in summer and autumn/2020. Regarding electricity generation, the present work obtained 1.50 kWh/m3, therefore reaching similar values to other studies that used more traditional biomass sources.

Hybrid constructed wetlands integrated with microbial fuel cells and reactive bed filter for wastewater treatment and bioelectricity generation.

The present study aimed to develop a pilot-scale integrated system composed of anaerobic biofilter (AF), a floating treatment wetland (FTW) unit, and a vertical flow constructed wetland coupled with a microbial fuel cell (CW-MFC) and a reactive bed filter (RBF) for simultaneously decentralized urban wastewater treatment and bioelectricity generation. The first treatment stage (AF) had 1450 L and two compartments: a settler and a second one filled with plastic conduits. The two CWs (1000 L each) were vegetated with mixed plant species, the first supported in a buoyant expanded polyethylene foam and the second (CW-MFC) filled with pebbles and gravel, whereas the RBF unit was filled with P adsorbent material (light expanded clay aggregate, or LECA) and sand. In the CW-MFC units, 4 pairs of electrode chambers were placed in different spacing. First, both cathode and anode electrodes were composed of graphite sticks and monitored as open circuit. Later, the cathode electrodes were replaced by granular activated carbon (GAC) and monitored as open and closed circuits. The combined system efficiently reduced COD (> 64.65%), BOD5 (81.95%), N-NH3 (93.17%), TP (86.93%), turbidity (94.3%), and total coliforms (removal of three log units). Concerning bioenergy, highest voltage values were obtained with GAC electrodes, reaching up to 557 mV (open circuit) and considerably lower voltage outputs with closed circuit (23.1 mV). Maximum power densities were obtained with 20 cm (0.325 mW/m2) and 30 cm (0.251 mW/m2). Besides the electrode superficial areas, the HRT and the water level may have influenced the voltage values, impacting DO and COD concentrations in the wastewater.

Floating treatment wetlands in domestic wastewater treatment as a decentralized sanitation alternative.

Floating treatment wetlands (FTW) are technologies that have stood out for their efficiency, ease of installation and maintenance. They consist of macrophytes emerging in a floating structure that keep the plant roots in direct contact with the effluent regardless of the water flow variation over time, allowing the removal of pollutants by various processes. The application of FTWs for the treatment of domestic wastewater has the advantage of low costs in terms of removing nutrients and at the same time reducing the cost of maintenance and energy consumption when compared to the conventional centralized treatment of effluent. The lack of wastewater treatment in areas distant from urban centers is even more limited, mainly due to the high cost of tubing and pumps for the effluent to reach the treatment plants. Therefore, the objective of this study was to research FTW systems applied to the decentralized treatment of domestic wastewater. First, a bibliometric analysis was conducted comparing the main issues involving FTW, and the challenges regarding the integration of FTW and domestic wastewater treatment systems. The feasibility of the floating system as a decentralized treatment approach were discussed, as well as the removal of nutrients in domestic wastewater, which was the most covered topic by researchers who developed studies in the area. In addition, other technologies are being integrated into the phytoremediation systems seeking to improve the quality of the treated effluent and assessing the potential reuse in the homes where they are generated and treated, determining the costs and space requirements for the entire process. There is a large research gap regarding the treatment of domestic wastewater by FTW in decentralized systems, mainly in terms of operation, cost assessment and reuse Therefore, further investigations in order to better understand the performance of the process and the reactions that occur with physical, chemical and microbiological removal mechanisms are still necessary.

Floating treatment wetlands integrated with microbial fuel cell for the treatment of urban wastewaters and bioenergy generation.

The objective of the present study was to develop a combined system composed of anaerobic biofilter (AF) and floating treatment wetlands (FTW) coupled with microbial fuel cells (MFC) in the buoyant support for treating wastewater from a university campus and generate bioelectricity. The raw wastewater was pumped to a 1450 L tank, operated in batch flow and filled with plastic conduits. The second treatment stage was composed of a 1000 L FTW box with a 200 L plastic drum inside (acting as settler in the entrance) and vegetated with mixed ornamental plants species floating in a polyurethane support fed once a week with 700 L of wastewater. In the plant roots, graphite rods were placed to act as cathodes, while on the bottom of the box 40 graphite sticks inside a plastic hose with a stainless-steel cable acting as the anode chamber. Open circuit voltages were daily measured for 6 weeks, and later as closed circuit with the connection of 1000 Ω resistors. Plant harvestings were conducted, in which biomass production and plant uptake from each of the species were measured. On average, system was efficient in reducing BOD5 (55.1%), COD (71.4%), turbidity (90.9%) and total coliforms (99.9%), but presented low efficiencies regarding total N (8.4%) and total P (11.4%). Concerning bioenergy generation, voltage peaks and maximum power density were observed on the feeding day, reaching 225 mV and 0.93 mW/m2, respectively, and in general decaying over the 7 days. In addition, plant species with larger root development presented higher voltage values than plants with the smaller root systems, possible because of oxygen release. Therefore, the combined system presented potential of treating wastewater and generating energy by integrating FTW and MFC, but further studies should investigate the FTW-MFC combination in order to improve its treatment performance and maximize energy generation.

Toxicity evaluation of hospital laundry wastewaters treated by microbial fuel cells and constructed wetlands.

Hospital laundries generate high wastewater volumes with the presence of several contaminants. Nevertheless, few studies have investigated the toxicity of these effluents and looked for treatment alternatives that might reduce this eventual toxicity. So, the present study assessed the performance of an integrated system combining a microbial fuel cell (MBFC) and a constructed wetland (CW) to reduce toxic effects of wastewaters generated at a hospital laundry. After collection, raw effluents remained 7 days at the first unit (MBFC) of integrated system. Afterward, they were transferred to the second unit (CW) unit where remained more 7 days totaling a hydraulic detention time of 14 days. The toxicity evaluation involved three different organisms: Daphnia magna (acute ecotoxicity), Lactuca sativa (phytotoxicity) and Allium cepa (phytotoxicity, cytotoxicity, mutagenicity, and genotoxicity). Got results revealed an extremely acute ecotoxicity against D. magna, high phytotoxic effects in the L. sativa and A. cepa assays, and genotoxicity in the A. cepa assay for the untreated effluents. Furthermore, no significant incidence of micronuclei was observed in the raw wastewaters. Regarding the treatment, after the first stage, it was possible to verify that MBFC reduced the toxicity of the wastewaters only in some tested assays (endpoints) while after the CW (second stage) the effluents presented a complete absence of toxicity of the investigated bioassays. Therefore, the use of the integrated system combining two environmentally friendly technologies can be considered promising, since both MBFC and CW presented a complimentary effect with excellent results regarding the reduction of the overall toxicity of hospital laundry wastewaters.

Biomonitoring of urban wastewaters treated by an integrated system combining microalgae and constructed wetlands.

The objectives of the present study were to apply different, toxicological assays for monitoring the toxicity of treated and untreated urban effluents produced at a university campus. The research was conducted at the wastewater treatment plant of the University of Santa Cruz do Sul, (UNISC), from october 2018 to april 2019. An integrated system with, anaerobic reactor (AR), microalgae (MA) and constructed wetlands (CWs) was, proposed for detoxification of the wastewaters produced at the university campus with a hydraulic detention time of 17 days. Daphnia, magna (ecotoxicity) and Allium cepa (phytotoxicity, cytotoxicity, and, genotoxicity) were used as tools to monitor the efficiency of the integrated system. Obtained results showed that the integrated system (MA, + CWs) presented good COD and BOD5 reductions, besides removal rates of, almost 98% for N-NH3, being much more efficient than the UNISC wastewater, treatment plant (UWTTP). The results of ecotoxicity presented the raw wastewaters (RW) as slightly toxic and an absence of ecotoxicity in all the treatments steps. Regarding phytotoxicity, the results showed no significant differences between the treatments. The cytogenetic assays indicated a significant increase in mitotic index (MI) (p < 0.001) after treatment by CWs compared to the final treatment UWTTP while the results, regarding binucleated cells (BNC) did not present significant differences, among the treatments. Micronucleus (MN) indexes were significantly different between the UWWPT and the integrated system (p < 0.01). In relation to chromosome aberrations (CA) the results indicate a significant difference between the CWs and UWWTP treatments (p < 0.01) and, RW and CWs (p < 0.001), confirming the detoxifying potential of the integrated system when compared to UWWPT. Thus, the results of the present research highlight the relevance in the proposition of the integrated system as an alternative of cleaner technology to the detriment of conventional technologies applied in wastewater treatment.

Floating treatment wetlands: A review and bibliometric analysis.

Floating treatment wetlands (FTWs) have attained tremendous popularity for water purification purposes. Through this phyto-technology, naturally occurring macrophytes are allowed to grow on the water surface on a buoyant raft or a rigid support, keeping the plant roots permanently in contact with the water and removing pollutants via several processes. The objective of this study was to review studies that have developed FTWs and to perform a bibliometric analysis using three keywords: "Floating", "Treatment" and "Wetlands". From bibliometric analysis using VOSviewer software and the Web of Science database, it was possible to verify the number of publications over the years and the countries and authors with the most published articles on these systems and other related terms. Subsequently, a review was performed on the main mechanisms of pollutant removal by FTWs as well as experiences and recommendations for major design and operating aspects for their application, such as water depth, hydraulic retention time (HRT), floating mat, water surface coverage, artificial aeration, plant selection and pruning or harvesting. It was verified that FTWs are a potential technology for treating several wastewater types and water remediation under different conditions. Even with the increasing number of publications in recent years, many design and operation aspects related to system performance still demand more research in order to better understand the relations between macrophytes and other pollutant removal mechanisms and to thereby improve the treatment efficiency of FTW systems.

Combined system for the treatment and reuse of urban wastewater: the efficiency of anaerobic reactors + hybrid constructed wetlands + ozonation.

The research developed a combined system in batch flow and in pilot scale for the treatment and reuse of urban effluents. The system was fed raw effluent from a university campus in Brazil and composed of four anaerobic reactors, three constructed wetlands (CWs) and an ozonation unit. The three sequential hybrid constructed wetlands were composed of a floating treatment wetland, an aerobic-anoxic baffled constructed wetland (CW) and a saturated vertifcal flow CW. Later, during the last trimester, weekly samples of the treated effluent were ozonated by bubbling with an application rate of 240 mg.h-1 O3. The system presented high removal rates efficiencies in terms of carbonaceous organic matter (78.9%), nitrogen (91.0%), color (96.7%) and turbidity (99.1%). In addition, it worked well for disinfection and acute ecotoxicity, but P was only efficiently (75%) removed in the first 8 months, with removing efficiency declining after this period. Ozonation provided significant color removal and an increased pH. The combination of floating, alternated upflow and downflow and saturated vertical flows improved the treatment of wastewater. This was due to the presence of both aerobic and anaerobic zones, as well as the filter substrate, through an integrated system with simple construction and operation and increased lifespan.

Performance of an integrated system combining microalgae and vertical flow constructed wetlands for urban wastewater treatment.

The present study investigated the performance of an integrated system, combining the sequential use of microalgae (MA) and vertical flow constructed wetland (VFCW) for the treatment of wastewaters produced at a university campus. Ecotoxicity and phytotoxicity assays were performed using respectively Daphnia magna and Lactuca sativa, whereas the genotoxicity of the wastewaters was assessed by using D. magna and Allium cepa. The results revealed that the major environmental impacts of the studied wastewaters are associated with the high eutrophication potential, due to high N-NH3 (68.8 ± 25.7 mg L-1), total P (7.71 ± 2.5 mg L-1), and BOD5 (526.4 ± 177 mg L-1) values, pathogenic load, and genototoxicity (p < 0.0001). The results also showed that the integrated system (MA + VFCW) was not able to satisfactory reduce the total p values (only 4%). Nevertheless, the MA + VFCW system achieved very promising results for the nitrogen removal, with emphasis on N-NH3 removal (100%) and the highest BOD5 removal (57%). Neither the raw wastewaters nor the treated wastewaters were phytotoxic. The integrated system completely eliminated the ecotoxicity (100%) and genotoxicity (n.s.) of the raw wastewater and showed decontamination potential. Thus, the integrated system emerges as an innovative environmental technology and, with minor adjustments, might be efficiently used in large scale and eventually replace conventional wastewater treatment systems.

Combined use of VUV and UVC photoreactors for the treatment of hospital laundry wastewaters: Reduction of load parameters, detoxification and life cycle assessment of different configurations.

The present research investigated the treatment of hospital laundry wastewaters by the combined use of photochemical VUV and UVC reactors. Seven different configurations were tested and the performances of each of them were evaluated based on the removal of the load parameters, detoxification and life cycle assessment (LCA). The characterization of studied wastewaters included analysis of the following parameters: COD, BOD5, TKN, total P, pH, turbidity and conductivity. Acute ecotoxicity was evaluated using Daphnia magna. Ultraviolet-Visible (UV-Vis) spectroscopy was performed to determine the organic fraction and chromatography coupled to the mass spectrometer (GC-MS) was used for the qualitative characterization of priority pollutants. Characterization parameters showed the presence of drugs like lidocaine and dipyrone and a high organic load with a poor biodegradability. Wastewaters presented an extreme acute toxicity against D. magna (EC50 6.7%). The ozonation process (mainly generated by the VUV reactor) obtained the best results concerning the ratio between the consumed energy and the removed COD and the UVC process presented the lowest environmental impacts for the characterization and normalization parameters of the LCA. Normalization revealed that the highest environmental burdens were associated with human toxicity, ecotoxicity and eutrophication of surface waters as well as to the use of non-renewable resources. VUV/UVC/O3 process presented the best results considering detoxification (EC50 100%).

Degradation of cyclophosphamide and 5-fluorouracil by UV and simulated sunlight treatments: Assessment of the enhancement of the biodegradability and toxicity.

The presence of pharmaceuticals in the environment has triggered concern among the general population and received considerable attention from the scientific community in recent years. However, only a few publications have focused on anticancer drugs, a class of pharmaceuticals that can exhibit cytotoxic, genotoxic, mutagenic, carcinogenic and teratogenic effects. The present study investigated the photodegradation, biodegradation, bacterial toxicity, mutagenicity and genotoxicity of cyclophosphamide (CP) and 5-fluorouracil (5-FU). The photodegradation experiments were performed at a neutral to slight pH range (7-7.8) using two different lamps (medium-pressure mercury lamp and a xenon lamp). The primary elimination of the parent compounds was monitored by means of liquid chromatography tandem mass spectrometry (LC-IT-MS/MS). NPOC (non-purgeable organic carbon) analyses were carried out in order to assess mineralization rates. The Closed Bottle Test (CBT) was used to assess ready biodegradability. A new method using Vibrio fischeri was adopted to evaluate toxicity. CP was not degraded by any lamp, whereas 5-FU was completely eliminated by irradiation with the mercury lamp but only partially by the Xe lamp. No mineralization was observed for the experiments performed with the Xe lamp, and a NPOC removal of only 18% was registered for 5-FU after 256 min using the UV lamp. Not one of the parent compounds was readily biodegradable in the CBT. Photo transformation products (PTPs) resulting from photolysis were neither better biodegradable nor less toxic than the parent compound 5-FU. In contrast, the results of the tests carried out with the UV lamp indicated that more biodegradable and non-toxic PTPs of 5-FU were generated. Three PTPs were formed during the photodegradation experiments and were identified. The results of the in silico QSAR predictions showed positive mutagenic and genotoxic alerts for 5-FU, whereas only one of the formed PTPs presented positive alerts for the genotoxicity endpoint.

Removal of the anti-cancer drug methotrexate from water by advanced oxidation processes: Aerobic biodegradation and toxicity studies after treatment.

Anti-cancer drugs are discussed as high risk substances in regard to human health and considered as problematic for the environment. They are of potential environmental relevance due to their poor biodegradability and toxicological properties. Methotrexate (MTX) is an antimetabolite that was introduced in the pharmaceutical market in the 40's and still today is one of the most consumed cytotoxic compounds around the world. In the present study MTX was only partially biodegraded in the closed bottle test (CBT). Therefore, it was submitted to three different advanced oxidation processes (AOPs): UV/H2O2, UV/Fe(2+)/H2O2 and UV/TiO2. The irradiation was carried out with a Hg medium-pressure lamp during 256min whereas the analytical monitoring was done through LC-UV-MS/MS and DOC analysis. MTX was easily removed in all the irradiation experiments, while the highest mineralization values and rates were achieved by the UV/Fe(2+)/H2O2 treatment. The lowest resulted from the UV/H2O2 reactions. The UV/H2O2 treatment resulted in little biodegradable transformation products (TPs). However, the same treatment resulted in a reduction of the toxicity of MTX by forming less toxic TPs. Analysis by LC-UV-MS/MS revealed the existence of nine TPs formed during the photo-catalytic treatments. The pH of the solutions decreased from 6.4 (t 0min) to 5.15 in the UV/H2O2 and from 6.4 (t 0min) to 5.9 in the UV/TiO2 at the end of the experiments. The initial pH of the UV/Fe(2+)/H2O2 experiments was adjusted to 5 and after the addition of H2O2 the pH decreased to around 3 and remained in this range until the end of the treatments.

Evaluation of the toxic effects of four anti-cancer drugs in plant bioassays and its potency for screening in the context of waste water reuse for irrigation.

Anti-cancer drugs are compounds that are of high environmental relevance because of their lack of specific mode of action. They can be extremely harmful to living organisms even at low concentrations. The present study evaluated the toxic effects of four frequently used anti-cancer drugs against plant seedlings, namely Cyclophosphamide (CP), Methotrexate (MTX), 5-Fluorouracil (5-FU) and Imatinib (IM). The phytotoxicity experiments were performed with Lactuca sativa seedlings whereas cytotoxicity, genotoxicity and mutagenicity investigations were performed with the well-established Allium cepa assays. MTX was the most phytotoxic compound, followed by 5-FU, CP and IM. Significant differences in the Mitotic Indexes (MI) were observed in three of the studied compounds (MTX, 5-FU and CP), indicating potential cytotoxic activity of these substances. Chromosome aberrations were registered in cells that were exposed to 5-FU, CP and IM. All the four compounds caused the formation of micronucleated cells indicating mutagenic potential. Besides, the assays performed with MTX samples presented a high number of cell apoptosis (cell death). Although it is unlikely that the pharmaceuticals concentrations measured in the environment could cause lethal effects in plants, the obtained results indicate that these compounds may affect the growth and normal development of these plants. So, both tests can constitute important tools for a fast screening of environmental contamination e.g. in the context of the reuse of treated wastewater and biosolids of agricultural purpose.

Degradation of 5-FU by means of advanced (photo)oxidation processes: UV/H2O2, UV/Fe2+/H2O2 and UV/TiO2--Comparison of transformation products, ready biodegradability and toxicity.

The present study investigates the degradation of the antimetabolite 5-fluorouracil (5-FU) by three different advanced photo oxidation processes: UV/H2O2, UV/Fe(2+)/H2O2 and UV/TiO2. Prescreening experiments varying the H2O2 and TiO2 concentrations were performed in order to set the best catalyst concentrations in the UV/H2O2 and UV/TiO2 experiments, whereas the UV/Fe(2+)/H2O2 process was optimized varying the pH, Fe(2+) and H2O2 concentrations by means of the Box-Behnken design (BBD). 5-FU was quickly removed in all the irradiation experiments. The UV/Fe(2+)/H2O2 and UV/TiO2 processes achieved the highest degree of mineralization, whereas the lowest one resulted from the UV/H2O2 treatment. Six transformation products were formed during the advanced (photo)oxidation processes and identified using low and high resolution mass spectrometry. Most of them were formed and further eliminated during the reactions. The parent compound of 5-FU was not biodegraded, whereas the photolytic mixture formed in the UV/H2O2 treatment after 256 min showed a noticeable improvement of the biodegradability in the closed bottle test (CBT) and was nontoxic towards Vibrio fischeri. In silico predictions showed positive alerts for mutagenic and genotoxic effects of 5-FU. In contrast, several of the transformation products (TPs) generated along the processes did not provide indications for mutagenic or genotoxic activity. One exception was TP with m/z 146 with positive alerts in several models of bacterial mutagenicity which could demand further experimental testing. Results demonstrate that advanced treatment can eliminate parent compounds and its toxicity. However, transformation products formed can still be toxic. Therefore toxicity screening after advanced treatment is recommendable.

Photodegradation of the antineoplastic cyclophosphamide: a comparative study of the efficiencies of UV/H2O2, UV/Fe2+/H2O2 and UV/TiO2 processes.

Anticancer drugs are harmful substances that can have carcinogenic, mutagenic, teratogenic, genotoxic, and cytotoxic effects even at low concentrations. More than 50 years after its introduction, the alkylating agent cyclophosphamide (CP) is still one of the most consumed anticancer drug worldwide. CP has been detected in water bodies in several studies and is known as being persistent in the aquatic environment. As the traditional water and wastewater treatment technologies are not able to remove CP from the water, different treatment options such as advanced oxidation processes (AOPs) are under discussion to eliminate these compounds. The present study investigated the degradation of CP by three different AOPs: UV/H2O2, UV/Fe(2+)/H2O2 and UV/TiO2. The light source was a Hg medium-pressure lamp. Prescreening tests were carried out and afterwards experiments based on the optimized conditions were performed. The primary elimination of the parent compounds and the detection of transformation products (TPs) were monitored with LC-UV-MS/MS analysis, whereas the degree of mineralization was monitored by measuring the dissolved organic carbon (DOC). Ecotoxicological assays were carried out with the luminescent bacteria Vibrio fischeri. CP was completely degraded in all treatments and UV/Fe(2+)/H2O2 was the fastest process, followed by UV/H2O2 and UV/TiO2. All the reactions obeyed pseudo-first order kinetics. Considering the mineralization UV/Fe(2+)/H2O2 and UV/TiO2 were the most efficient process with mineralization degrees higher than 85%, whereas UV/H2O2 achieved 72.5% of DOC removal. Five transformation products were formed during the reactions and identified. None of them showed significant toxicity against V. fischeri.

Ecotoxicological and genotoxic assessment of hospital laundry wastewaters.

The aim of the present study was to assess the ecotoxicity and genotoxicity of hospital laundry wastewaters generated from a regional hospital located in Rio Pardo Valley in the state of Rio Grande do Sul, Brazil. Physicochemical, microbiological, ecotoxicological, and genotoxic analyses were performed, and the results indicate that some parameters were not in accordance with the limit concentrations established by Brazilian and international guidelines for urban wastewaters. Daphnia magna (EC50 2.01%) and Danio rerio (LC50 29.25%) acute toxicity was detected, and sublethal effects were identified in Lactuca sativa (IC25 12.50%) and Allium cepa (IC25 51.25%). Cytotoxicity was observed at the five wastewater concentrations used yielding statistically significant differences (p < 0.05) in the meristematic cells of A. cepa compared with the negative control. The results obtained here warn about the necessity to develop treatment methods that can mitigate the environmental impacts caused by the ecotoxicity and genotoxicity of hospital laundry wastewaters.