Microplastics occurrence and fate in full-scale treatment wetlands.

Treatment wetlands (TWs) are an efficient technology for removing microplastics (MPs) from wastewater, according to previous studies. This study investigates the dynamics and fate of MPs in two wastewater treatment plants (WWTPs) using TWs, one with horizontal subsurface flow (HF) and another with a floating plant system (FS). Special attention is paid to the retention produced in the sludge and the role of macrophyte roots. The abundance of MPs in the influent to the WWTPs was on average 20.3 ± 0.85 MP/L and 8.4 ± 1.13 MP/L in HF and FS respectively, while the effluent had 0.58 ± 0.07 MP/L and 0.17 ± 0.06 MP/L, thus giving overall efficiencies of 97.42% and 98.13%, respectively. In the HF wetland, sludge samples near the inlet and the outlet were taken, distinguishing between sludge adhered to gravel and sludge attached to roots. In the floating macrophytes, sludge samples from secondary and tertiary treatments were taken. The results indicate that roots play a significant role in MPs retention. In the HF wetland, the complex formed by roots and gravel attached more MPs than gravel alone in the final zone of the wetland. In the FS, roots retained a significant quantity of MPs, both in the secondary and tertiary treatments, thus giving rise to a sludge less concentrated in MPs. This study aims to improve the knowledge of MPs behavior and fate in full-scale TWs, providing valuable information to enhance retention efficiency.

Assessment of the properties of aging biochar used as a substrate in constructed wetlands.

Biochar has gained global recognition as an effective tool for environmental remediation, and is increasingly being used as an alternative substrate in constructed wetlands (CWs). While, most studies have focused on the positive effects of biochar for the pollutant removal in CWs, less is known about aging and longevity of the embedded biochar. This study investigated the aging and stability of biochar embedded in CWs post-treating the effluent of a municipal and an industrial wastewater treatment plant. Litter bags containing biochar were inserted into two aerated horizontal subsurface flow CWs (350 m2 each), and retrieved on several dates (8-775 days after burial) for assessment of weight loss/gain and changes in biochar characteristics. Additionally, a 525-day laboratory incubation test was conducted to analyze biochar mineralization. The results showed that there was no significant biochar weight loss over time, but a slight increase in weight (2.3-3.0%) was observed at the end, likely due to mineral sorption. Biochar pH remained stable except for a sudden drop at the beginning (8.6-8.1), while the electrical conductivity continued to increase (96-256 µS cm-1) throughout the experiment. The sorption capacity of the aged biochar for methylene blue significantly increased (1.0-1.7 mg g-1), and a change in the biochar's elemental composition was also noted, with O-content increasing by 13-61% and C content decreasing by 4-7%. Despite these changes, the biochar remained stable according to the criteria of the European Biochar Foundation and International Biochar Initiative. The incubation test also showed negligible biochar mass loss (<0.02%), further validating the stability of the biochar. This study provides important insights into the evolution of biochar characteristics in CWs.

Water treatment and reclamation by implementing electrochemical systems with constructed wetlands.

Seasonal or permanent water scarcity in off-grid communities can be alleviated by recycling water in decentralized wastewater treatment systems. Nature-based solutions, such as constructed wetlands (CWs), have become popular solutions for sanitation in remote locations. Although typical CWs can efficiently remove solids and organics to meet water reuse standards, polishing remains necessary for other parameters, such as pathogens, nutrients, and recalcitrant pollutants. Different CW designs and CWs coupled with electrochemical technologies have been proposed to improve treatment efficiency. Electrochemical systems (ECs) have been either implemented within the CW bed (ECin-CW) or as a stage in a sequential treatment (CW + EC). A large body of literature has focused on ECin-CW, and multiple scaled-up systems have recently been successfully implemented, primarily to remove recalcitrant organics. Conversely, only a few reports have explored the opportunity to polish CW effluents in a downstream electrochemical module for the electro-oxidation of micropollutants or electro-disinfection of pathogens to meet more stringent water reuse standards. This paper aims to critically review the opportunities, challenges, and future research directions of the different couplings of CW with EC as a decentralized technology for water treatment and recovery.

Life cycle assessment of microalgae systems for wastewater treatment and bioproducts recovery: Natural pigments, biofertilizer and biogas.

The aim of this study was to assess the potential environmental impacts associated with microalgae systems for wastewater treatment and bioproducts recovery. In this sense, a Life Cycle Assessment was carried out evaluating two systems treating i) urban wastewater and ii) industrial wastewater (from a food industry), with the recovery of bioproducts (i.e. natural pigments and biofertilizer) and bioenergy (i.e. biogas). Additionally, both alternatives were compared to iii) a conventional system using a standard growth medium for microalgae cultivation in order to show the potential benefits of using wastewater compared to typical cultivation approaches. The results indicated that the system treating industrial wastewater with unialgal culture had lower environmental impacts than the system treating urban wastewater with mixed cultures. Bioproducts recovery from microalgae wastewater treatment systems can reduce the environmental impacts up to 5 times compared to a conventional system using a standard growth medium. This was mainly due to the lower chemicals consumption for microalgae cultivation. Food-industry effluent showed to be the most promising scenario for bioproducts recovery from microalgae treating wastewater, because of its better quality compared to urban wastewater which also allows the cultivation of a single microalgae species. In conclusion, microalgae wastewater treatment systems are a promising solution not only for wastewater treatment but also to boost the circular bioeconomy in the water sector through microalgae-based product recovery.

Performance of a green wall (Total Value Wall™) at high greywater loading rates and Life Cycle Impact Assessment.

Nature-based greywater (GW) treatment and reuse in urban areas has become an up-and-coming option. A 14.4 m2 green wall system called Total Value Wall (TVW) was installed at a terraced house in Gent (Belgium) for treating GW and reusing the effluent for toilet flushing. In a previous study, the TVW was loaded at 7 L.m-2.d-1 and efficiently removed TSS (67%), COD (43%), BOD5 (83%) and total coliforms (log 2), but a number of issues were reported related to nutrient leaching from the substrate, and the excessive retention time in the storage tanks. In this study results are reported from a follow-up study during which an adapted TVW was subjected to both higher hydraulic and pollutant loading rates in order to investigate the treatment capability of TVW. The design of the system, i.e. substrate contained in geotextile bags, did not sustain the higher hydraulic loading rates as excessive leakage occurred. Despite this, the higher pollutant loading rates still resulted in an acceptable effluent quality with 15 mg.L-1 TSS (90%), 85 mg.L-1 COD (82%), and 15 mg.L-1 BOD5 (95%). Ammonium, E. coli and total coliforms were removed with removal rates of 98%, 63% (0.4 log units), and 36% (0.2 log units), respectively. Finally, a life cycle assessment (LCA) was performed for the TVW with and without treating GW to analyze the environmental burden. The LCA impacts showed that replacing tap water and chemical fertilizer by GW, and the reuse of effluent, have a positive impact. However, the energy use for pumping has a major impact and should be minimized by using an efficient pump and distribution system to reduce the overall footprint.

Towards a general kinetic microalgae model: Extending a semi-deterministic green microalgae model for the cyanobacterium Arthrospira platensis and red alga Porphyridium purpureum.

Mathematical models for microalgae and cyanobacteria are seldomly validated for different algal species, as such limiting their applicability. Therefore, in this research, a previously developed kinetic model describing the growth of the green microalgae species Chlorella vulgaris was used to simulate the growth of the cyanobacterium Arthrospira platensis and the red alga Porphyridium purpureum. Based on a global sensitivity analysis, the model parameter µmax,A was calibrated using respirometric-titrimetric data. Calibration yielded values of 5.76 ± 0.17 d-1, 2.06 ± 0.16 d-1 and 1.06 ± 0.09 d-1 for Chlorella vulgaris, Arthrospira platensis and Porphyridium purpureum, respectively. Model simulations revealed that the biological growth equations in this model are adequate. However, increased light intensities triggered a survival mechanism for Arthrospira platensis, which is currently not taken into account by the model, leading to bad model accuracy under these circumstances. Future work should address the most important survival mechanisms and include those in the model to widen its applicability.

Total value wall: Full scale demonstration of a green wall for grey water treatment and recycling.

Greywater treatment and reuse for non-potable purposes in urban areas has become a widely researched topic to reduce the burden on fresh water resources. This study reports on the use of a green wall for treating grey water and reusing the effluent for toilet flushing, called Total Value Wall (TVW). Initially, the effectiveness of (mixtures of) different substrates, i.e. lava, lightweight expanded clay aggregates, organic soil and biochar was investigated by means of column tests. All substrates were first examined for hydraulic characteristics and later on the columns were fed with synthetic grey wastewater and followed up in terms of removal efficiency of COD and detergents. The mixture consisting of lava (50%), organic soil (25%) and biochar (25%) proved to be optimal both in terms of percolation rates and removal efficiencies, and was thus selected for the full-scale system. The full-scale TVW of 14.4 m2 was installed at a terraced house in Ghent (Belgium), and was loaded with grey water at 100 L per day. Influent and effluent quality were routinely monitored by grab sampling, water savings were monitored by means of flow meters, and electricity consumption was also accounted for. The TVW was further equipped with sensors that measure temperature, Particulate Matter (PM10) and CO2 in the air. The full-scale system obtained effluent concentrations of 13 mg.L-1 TSS, 91 mg.L-1 COD and 5 mg.L-1 BOD5. Ammonium and total coliforms were removed with removal rates of 97% and 99% (2 log units) respectively. However, an increase in effluent concentration of nitrate and phosphate was observed due to leaching from the selected substrate. Available data from the temperature sensors have clearly demonstrated the additional benefit of the TVW as an insulating layer, keeping the heat outside on warmer days, and keeping the heat inside on colder days. Overall, this study demonstrated that the TVW is a sustainable system for greywater treatment and reuse.

Roof runoff contamination: Establishing material-pollutant relationships and material benchmarking based on laboratory leaching tests.

Because roofs represent a major part of the urban impervious surface, it is hypothesized that roof runoff is an important source of urban stormwater contamination. However, the contribution of different roofing materials to this contamination has only been examined to a limited extent. In this study, a resource and time efficient methodology, which uses some of the principles of a standardized leaching test (CEN/TS16637-2), was developed to identify material-pollutant relationships for sixteen commonly used roofing materials (EPDM, PVC, TPO, EVA, PU and bitumen membranes). Metals were detected in concentrations ranging from several µg/L in the leachate of synthetic materials up to 2.5 mg/L for Zn in the leachate of EPDM materials. Cd and Cr were not detected in any of the leachates. Furthermore, polycyclic aromatic hydrocarbons were detected in most leachates, with phenanthrene and naphthalene being most frequently detected in concentrations up to 4.5 µg/L for naphthalene. Further insights on organic pollutants' leaching from the tested materials were obtained by a non-target GC-MS screening of the leachates. Several commonly used additives such as flame retardants and light stabilizers were detected. Although no information on long-term leaching and material behavior under outdoor conditions could be obtained by the developed methodology, the laboratory test results could be used to benchmark the materials for their potential impact on roof runoff quality by the calculation of material indexes (which summarize the material-pollutant relationships). EPDM and PU roofing materials were identified as the materials having the highest potential to affect roof runoff quality.

Model based analysis of carbon fluxes within microalgae-bacteria flocs using respirometric-titrimetric data.

With the emerging need of nutrient recycling in resource recovery facilities, the use of microalgae-bacteria flocs has received considerable attention in the past few years. However, although the main biological processes are already known, the complex interactions occurring between algae and bacteria are not fully understood. In this work, a combined respirometric-titrimetric unit was used to assess the microorganisms' kinetics within microalgae-bacteria flocs under different growth regimes (i.e. photoautotrophic, heterotrophic and mixotrophic) and different ratios of inorganic (IC) to organic carbon (OC) (IC:OC-ratios). Using this respirometric-titrimetric data, a new model was developed, calibrated and successfully validated. The model takes into account the heterotrophic growth of bacteria, the photoautotrophic, heterotrophic and mixotrophic growth of algae and the production and consumption of extracellular polymeric substances (EPS) by both bacteria and algae. As such, the model can be used for detailed analysis of the carbon fluxes within microalgae-bacteria flocs in an efficient way. Model analysis revealed the high importance of the EPS regulatory mechanism. Firstly, under heterotrophic growth conditions, OC-uptake occurred during the first 10-15 min. This was linked with internal OC storage (49% of added OC) and EPS production (40%), as such providing carbon reserves which can be consumed during famine conditions. Moreover, the algae were able to compete with bacteria for OC. Secondly, under photoautotrophic conditions, algae used the added IC to grow (57% of added IC) and to produce EPS (29%), which consecutively stimulated heterotrophic bacteria growth (20%). Finally, under mixotrophic conditions, low IC:OC-ratios resulted in an extensive OC-storage and EPS production (50% of added C) and an enhanced microalgal CO2 reuse, resulting in an increased algal growth of up to 29%.

Fate and removal of microplastics in unplanted lab-scale vertical flow constructed wetlands.

Many studies have reported conventional wastewater treatment plants as one of the main sources of microplastics (MPs). However, constructed wetlands (CWs) as a nature-based wastewater treatment system have received little attention. This study investigated the influence of biofilm, media type and earthworms on the fate and removal of MPs in a short-term (45d) experiment with unplanted lab-scale vertical flow CWs (VFCWs). In sand-filled VFCWs, MPs were retained in the first 10 cm, and the removal efficiency was 100%, regardless of the presence of a biofilm. When gravel was used as filling material, the removal efficiency of MPs was stable at 96%, but the MPs were distributed throughout the 80 cm high VFCWs. In the presence of earthworms, the maximum depth that MPs reached within sand-filled VFCWs increased from 10 to 15 cm. Furthermore, the MPs concentration at a depth of 3-6 cm and 6-10 cm increased 2 and 10 fold respectively compared to the same VFCWs without earthworms. Although no MPs were detected in the sand from deep layers (15-80 cm), transport of MPs from top to the bottom by earthworms was found, and a few MPs were detected in the effluent, leading to a removal efficiency of 99.8%. This study indicated that both a higher media grain size and the presence of earthworms have a small effect on the removal efficiency of MPs in VFCWs, but the effect on the distribution of MPs was considerably. Longer-term studies in full-scale CWs are advised to perform under the influence of more practical factors.

Constructed wetlands operated as bioelectrochemical systems for the removal of organic micropollutants.

The removal of organic micropollutants (OMPs) has been investigated in constructed wetlands (CWs) operated as bioelectrochemical systems (BES). The operation of CWs as BES (CW-BES), either in the form of microbial fuel cells (MFC) or microbial electrolysis cells (MEC), has only been investigated in recent years. The presented experiment used CW meso-scale systems applying a realistic horizontal flow regime and continuous feeding of real urban wastewater spiked with four OMPs (pharmaceuticals), namely carbamazepine (CBZ), diclofenac (DCF), ibuprofen (IBU) and naproxen (NPX). The study evaluated the removal efficiency of conventional CW systems (CW-control) as well as CW systems operated as closed-circuit MFCs (CW-MFCs) and MECs (CW-MECs). Although a few positive trends were identified for the CW-BES compared to the CW-control (higher average CBZ, DCF and NPX removal by 10-17% in CW-MEC and 5% in CW-MFC), these proved to be not statistically significantly different. Mesoscale experiments with real wastewater could thus not confirm earlier positive effects of CW-BES found under strictly controlled laboratory conditions with synthetic wastewaters.

Natural Pigments and Biogas Recovery from Microalgae Grown in Wastewater.

This study assessed the recovery of natural pigments (phycobiliproteins) and bioenergy (biogas) from microalgae grown in wastewater. A consortium of microalgae, mainly composed by Nostoc, Phormidium, and Geitlerinema, known to have high phycobiliproteins content, was grown in photobioreactors. The growth medium was composed by secondary effluent from a high rate algal pond (HRAP) along with the anaerobic digestion centrate, which aimed to enhance the N/P ratio, given the lack of nutrients in the secondary effluent. Additionally, the centrate is still a challenging anaerobic digestion residue since the high nitrogen concentrations have to be removed before disposal. Removal efficiencies up to 52% of COD, 86% of NH4 +-N, and 100% of phosphorus were observed. The biomass composition was monitored over the experimental period in order to ensure stable cyanobacterial dominance in the mixed culture. Phycocyanin and phycoerythrin were extracted from harvested biomass, achieving maximum concentrations of 20.1 and 8.1 mg/g dry weight, respectively. The residual biomass from phycobiliproteins extraction was then used to produce biogas, with final methane yields ranging from 159 to 199 mL CH4/g VS. According to the results, by combining the extraction of pigments and the production of biogas from residual biomass, we would not only obtain high-value compounds, but also more energy (around 5-10% higher), as compared to the single recovery of biogas. The proposed process poses an example of resource recovery from biomass grown in wastewater, moving toward a circular bioeconomy.

Water treatment and re-use at temporary events using a mobile constructed wetland and drinking water production system.

Temporary events such as music festivals are often organized in places that are not connected to a sewage network. As such, the waste (water) generated and discharged can place a heavy burden on the environment. A mobile vertical flow constructed wetland (MCW) with an area of 15 m2 was constructed, optimized and operated for three years treating grey water (GW) as well as grey and black water (GW + BW) at different festival locations to tackle this problem. During the initial development phase, the appropriate influent type (GW and/or GW + BW) was determined and challenge tests with pre-settled diluted domestic waste water (mimicking GW) were carried out to determine the maximal allowable loading rate. The MCW was able to treat both types of water. However, for further experiments GW was selected as the discharge limits could not be met when treating GW + BW. The challenge tests demonstrated that the MCW could be operated at a maximal allowable hydraulic loading rate of 1.1 m3·m-2·d-1, corresponding to mass loading rates of 68 gTSS·m-2·d-1, 160 gCOD·m-2·d-1 and 137 gBOD·m-2·d-1. During treatment of GW, the MCW achieved effluent concentrations for respectively chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solids (TSS) and total phosphorus (TP) of 43 mg·L-1, 16 mg·L-1, 2.7 mg·L-1 and 1.7 mgP·L-1. This corresponds to a removal of 90% (COD), 95% (BOD), 97% (TSS) and 76% (TP) respectively. Total nitrogen removal was 25% (from 45 mgN·L-1 to 34 mgN·L-1) as particularly denitrification was not complete. As a further development, the MCW was coupled to a drinking water treatment system using ultrafiltration and reverse osmosis (UF-RO) membranes to produce potable water on site. The drinking water system produced potable water that met the legislative criteria. As such, a sustainable and mobile water treatment system aiming at producing potable water at temporary events was demonstrated.

Characteristics and removal of microplastics in rural domestic wastewater treatment facilities of China.

The environment of the countryside is different from that of the city. Studying the abundance, characteristics, and removal of microplastics (MPs) in rural domestic wastewater treatment facilities (RD-WWTFs) is of great significance for understanding the impacts of human activities on the environment of the countryside. Therefore, we studied five such facilities in the Hangzhou region of China. The abundance of MPs in the influent was 430-2154 items/m3. Micro-Raman spectroscopic analysis indicates that the main type of polymer in the influent is polypropylene (PP, 54.6%), followed by polystyrene (PS, 29.7%) and polyethylene terephthalate (PET, 9.7%). The color of MPs is mainly white and clear (62.9%), red (13.3%) and gray (12.0%). Our results show that fragments (71.3%) are the dominant shape of MPs, followed by fibers (21.5%). The characteristics of MPs, such as sizes, shapes, and types, along with the treatment process, affect the removal of MPs in RD-WWTFs. Large MPs are easily removed by anaerobic processes, while small MPs are better removed by anaerobic/anoxic/oxic processes. Fibrous MPs are more difficult to be removed than the fragmented ones. Constructed wetlands play an important role in the removal of MPs.

Horizontal subsurface flow constructed wetlands as tertiary treatment: Can they be an efficient barrier for microplastics pollution?

The presence and fate of microplastics (MPs) in wastewater represent a subject of major concern, as wastewater is one of the main inputs of MPs to the environment. This study deals with the ability of horizontal subsurface-flow constructed wetlands (CWs), as tertiary treatment, to reduce the MPs concentration of secondary effluents. Different locations of a wastewater treatment plant (WWTP) including raw wastewater, CW influent and final effluent, were sampled. Macroinvertebrates were collected from the CW to evaluate their potential role in the MPs distribution along the wetland. The global WWTP efficiency for MPs removal was 98%. MPs removal efficiency by CW was on average 88%, causing a significant reduction of the MPs concentration from 6.45 to 0.77 MP/L (p < 0.05), thus preventing them from entering vulnerable aquatic systems. The areal removal rate and the first order areal rate coefficient (kA) were estimated to be 3120 MPs/m2/d and 1.70 m/d, respectively. The most abundant size fraction was the one comprising MPs between 75 and 425 µm (51%), while the other size ranges analysed (40-75 and 425-5600 µm) accounted for 25 and 24%, respectively. Fiber was the most abundant shape in the WWTP influent (75%), the CW influent (54%) and effluent (71%). Non-significant differences were found between sites regarding size and shape distributions (p > 0.05). Macroinvertebrates can ingest a non-negligible quantity of MPs, with an average content of 166.2 MPs/g or 0.13 MPs/individual. Therefore, they could play a certain role in the MPs distribution inside CWs. Fiber was the most abundant shape for macroinvertebrates as well (89%), so attention should be paid to reduce their contamination at source. This study provides the first results on MPs removal in CWs as tertiary treatment and assesses the potential role of macroinvertebrates in their distribution along the CW, thus filling this gap of knowledge.

Natural pigments from microalgae grown in industrial wastewater.

The aim of this study was to investigate the cultivation of Nostoc sp., Arthrospira platensis and Porphyridium purpureum in industrial wastewater to produce phycobiliproteins. Initially, light intensity and growth medium composition were optimized, indicating that light conditions influenced the phycobiliproteins production more than the medium composition. Conditions were then selected, according to biomass growth, nutrients removal and phycobiliproteins production, to cultivate these microalgae in food-industry wastewater. The three species could efficiently remove up to 98%, 94% and 100% of COD, inorganic nitrogen and PO43--P, respectively. Phycocyanin, allophycocyanin and phycoerythrin were successfully extracted from the biomass reaching concentrations up to 103, 57 and 30 mg/g dry weight, respectively. Results highlight the potential use of microalgae for industrial wastewater treatment and related high-value phycobiliproteins recovery.

Metals and metalloid in gold mine pit lakes and fish intake risk assessment, Burkina Faso.

This study aimed to determine the levels of metals and metalloid (arsenic) in pit lakes from a gold mining site and in their fishes and assess their potential health effect on the local human population, in order to evaluate whether pit lakes can be safely used for aquaculture. Water quality data were collected from two pit lakes, namely West Pit 1 (WP1) and West Pit 2 (WP2), and the Nakambé River (NR) in Burkina Faso. Fish consumption rates in different villages were assessed through a survey. Commonly available fish were sampled from the pit lakes and the NR. Fish from the pit lakes contained higher amounts of metals and metalloid than fish from the river (WP1 ~ WP2 < NR). Of the four species of fish considered, Oreochromis niloticus and Hydrocynus forskahlii had the highest metals and metalloid content and Bagrus bajad and Clarias anguillaris had the lowest. The results indicated that the consumption of the whole fish results in higher metals and metalloid intake than consumption of the fleshy part only. Due to the low fish intake of 5.34 ± 2.60 g/day/adult deduced from the nutritional survey, exposure to metals and metalloid was below referential doses. The highest arsenic intake comes from eating entire O. niloticus (0.058 mg/day/adult) from WP1. Eating O. niloticus and C. anguillaris exposes people to an arsenic intake of 0.01 mg/day/adult. The arsenic contents of H. forskahlii and B. bajad were below the method detection limit.

Trace element content in cereals from a gold mining site in Burkina Faso and intake risk assessment.

Cereals grown close to mining sites could contain high levels of trace elements which could jeopardize local population health through intake of those crops. This study investigated for the first time the concentration of trace elements, namely arsenic, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead and zinc in four types of cereals (two of maize and two of sorghum) grown within the perimeter of a gold mine and at three surrounding villages in Burkina Faso. A total of 47 samples were taken. Cereal consumption surveys in those villages were undertaken to evaluate the intake hazard. Average arsenic content trend was Site (0.31 ±â€¯0.56 mg kgdw-1) > Songo (0.18 ±â€¯0.17 mg kgdw-1) > Sighnoguin (0.15 ±â€¯0.10 mg kgdw-1) > Youga (0.10 ±â€¯0.00 mg kgdw-1); subsequently, the average estimated daily intake of Arsenic followed this pattern: Site > Songo > Sighnoguin > Youga with 1.93, 1.08, 0.89 and 0.63 µg kgbw-1 day-1 respectively which all fall below a target hazard quotient of 1. Non-parametric Kruskal-Wallis tests confirmed significant difference of Co, Cu, Fe, Mn and Ni between locations whilst not significant differences were found for As, Cd, Pb and Zn. Considering cereals types, yellow corn from the mine site exhibited As value higher than the Referential dose (2.14 µg kgbw-1 day-1) and consequently a target hazard quotient of 1.97. This finding indicates that there is an intake risk to the local population from dietary intake. Contamination by As could be linked to mining activities on parent rocks that contain As with spread by wind to Songo and Youga. Sighnoguin village is more subject to contamination by agricultural practices. Decontamination of the site and selection of cereals with low uptake capability and some changes to agricultural practices could reduce the hazards.

Influence of recirculation over COD and N-NH4 removals from landfill leachate by horizontal flow constructed treatment wetland.

Treatment of landfill leachate is a challenge due to its complex chemical composition and high recalcitrance and because of high costs for conventional wastewater treatment. In our study, leachate from the Quitaúna Landfill, Sao Paulo Metropolitan Region, Brazil, was treated at a laboratory scale with a horizontal subsurface flow constructed treatment wetland (HF-CTW) operating under a recirculation regime. Two units planted with Heliconia psittacorum (HP) and Cyperus papyrus (CP), and one unplanted control unit were assessed. With a recirculation regime over 21 days, the planted units removed 40% of chemical oxygen demand (COD) while the control unit removed only 29%. True color removal efficiencies were 2, 22, and 23% for the control, HP, and CP HF-CTWs, respectively. The ammonium nitrogen removal efficiencies for a 21-day hydraulic retention time (HRT) were 63-81% for planted units and 72% for the control. The increase of the HRT from 7 to 21 days led to the enhancement of ammonium nitrogen removal but did not affect the COD and total nitrogen removals. This phenomenon is a consequence of leachate's low biodegradability. The present study shows the importance of the HRT and plant presence for landfill leachate treatment using HF-CTWs.

The effect of primary treatment of wastewater in high rate algal pond systems: Biomass and bioenergy recovery.

The aim of this study was to assess the effect of primary treatment on the performance of two pilot-scale high rate algal ponds (HRAPs) treating urban wastewater, considering their treatment efficiency, biomass productivity, characteristics and biogas production potential. Results indicated that the primary treatment did not significantly affect the wastewater treatment efficiency (NH4+-N removal of 93 and 91% and COD removal of 62 and 65% in HRAP with and without primary treatment, respectively). The HRAP without primary treatment had higher biodiversity and productivity (20 vs. 15 g VSS/m2d). Biomass from both systems presented good settling capacity. Results of biochemical methane potential test showed that co-digesting microalgae and primary sludge led to higher methane yields (238-258 mL CH4/g VS) compared with microalgae mono-digestion (189-225 mL CH4/g VS). Overall, HRAPs with and without primary treatment seem to be appropriate alternatives for combining wastewater treatment and bioenergy recovery.