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Anthropogenic nutrient input stimulates surface eutrophication and algal blooms and thus exacerbates oxygen depletion and hypoxia in aquatic ecosystems. However, existing studies have paid little attention on the understanding of the feedback relationships among oxygen consumption, algal succession and greenhouse gas effect after river damming, particularly in Three Gorges Reservoir. This field work investigated the thermal stratification, water quality and phytoplankton in four tributaries (Pengxi Bay (PXB), Daning Bay (DNB), Shennong Bay (SNB), and Xiangxi Bay (XXB)) of the Three Gorges Reservoir (TGR) in spring (April 25-28, 2022), and explored the drivers of hypoxia and its feedback response to algal blooms and methane (CH4) emissions. The results showed that during the observation period, DO, thermal stratification, and algal blooms were more severe in PXB. The high Chemical Oxygen Demand (CODMn) (11.27 mg•L-1) and Dissolved Organic Carbon (DOC) content (7.56 mg•L-1) in PXB were the main causes of the progressive hypoxia. Furthermore, stronger density stratification in PXB inhibited the vertical supply of DO and accelerated bottom hypoxia. But the downslope density current replenished bottom DO in the upper reaches of the DNB, SNB, and XXB. The CH4 concentration was generally higher in hypoxia zone, especially in where cyanobacteria are the dominant species (eg., PX03 and PX04). Dam construction led to the succession of algal-dominant species, exerting a significant influence on the river carbon cycle. The expansion of cyanobacterial blooms and the consequence of metabolic substrates increase are gradually increasing oxygen deprivation, even hypoxia, and enhancing CH4 production in rivers. These findings suggest that the succession of algal-dominant species caused by river damming has a pronounced positive feedback effect on reservoir hypoxia processes and greenhouse effect. [ABSTRACT FROM AUTHOR]

The ability of several mesocosm-scale horizontal subsurface flow (SSF) constructed wetlands (CW) to remove pharmaceuticals and personal care products (PPCPs) from urban wastewater was assessed in the winter and summer of 2008. As CWs are generally used as secondary or tertiary wastewater treatment systems, their efficacy was compared when fed from two different primary treatment systems, a sedimentation tank and an anaerobic hydrolysis upflow sludge bed reactor (HUSB). The influence of plants (Phragmites australis) in the CWs and their feeding regime (continuous flow or batch flow) on PPCP removal were also monitored. One of the CWs was replicated and operated simultaneously in Barcelona and Leon, Spain, in order to study the effect of environmental conditions on PPCP removal. All systems operated in the open air. The sedimentation tank offered slightly better removal values throughout the experimental period than the HUSB. The presence of P. australis enhanced the removal of salicylic acid, galaxolide, tonalide and methyl dihydrojasmonate, but only in summer (when plants were more active). The use of a batch flow or a continuous flow made very little difference to PPCP removal efficiency. When the two mesocosm replicates were compared, temperature proved to be one of the most determining parameters affecting PPCP elimination, with naproxen, ibuprofen, diclofenac, caffeine, galaxolide, tonalide and methyl dihydrojasmonate being removed in SSF-CWs more efficiently at higher temperatures. In general, the most easily removed PPCPs in planted CWs were caffeine (14 ± 74%-84 ± 7% in winter, 98 ± 1%-99 ± 1% in summer), methyl dihydrojasmonate (28 ± 21%-63 ± 17% in winter, 93 ± 2%-98 ± 1% in summer) and salicylic acid (0%-97 ± 4% in winter, 41 ± 40%-89 ± 9% in summer), followed by naproxen (0%-41 ± 16% in winter, 60 ± 18%-95 ± 4% in summer) and ibuprofen (0%-47 ± 26% in winter, 35 ± 12%-99 ± 1% in summer). Other substances experimented lower removal efficiencies, like ketoprofen (4 ± 27%-27 ± 14% in winter, 0%-37 ± 32% in summer), diclofenac (0%-22 ± 22% in winter, 0%-71 ± 8% in summer), carbamazepine (0%-9 ± 100% in winter, 0%-58 ± 21% in summer), galaxolide (0% in winter, 25 ± 14%-87 ± 5% in summer) and tonalide (0% in winter, 32 ± 12%-76 ± 12% in summer). [ABSTRACT FROM AUTHOR]

1. Changes in cladoceran subfossils in the surface sediments of 54 shallow lakes were studied along a European latitude gradient (36–68°N). Multivariate methods, such as regression trees and ordination, were applied to explore the relationships between cladoceran taxa distribution and contemporary environmental variables, with special focus on the impact of climate. 2. Multivariate regression tree analysis showed distinct differences in cladoceran community structure and lake characteristics along the latitude gradient, identifying three groups: (i) northern lakes characterised by low annual mean temperature, conductivity, nutrient concentrations and fish abundance, (ii) southern, macrophyte rich, warm water lakes with high conductivity and high fish abundance and (iii) Mid-European lakes at intermediate latitudes with intermediate conductivities, trophic state and temperatures. 3. Large-sized, pelagic species dominated a group of seven northern lakes with low conductivity, where acid-tolerant species were also occasionally abundant. Small-sized, benthic-associated species dominated a group of five warm water lakes with high conductivity. Cladoceran communities generally showed low species-specific preferences for habitat and environmental conditions in the Mid-European group of lakes. Taxon richness was low in the southern-most, high-conductivity lakes as well as in the two northern-most sub-arctic lakes. 4. The proportion of cladoceran resting eggs relative to body shields was high in the northern lakes, and linearly (negatively) related to both temperature and Chl a, indicating that both cold climate (short growing season) and low food availability induce high ephippia production. 5. Latitude and, implicitly, temperature were strongly correlated with conductivity and nutrient concentrations, highlighting the difficulties of disentangling a direct climate signal from indirect effects of climate, such as changes in fish community structure and human-related impacts, when a latitude gradient is used as a climate proxy. Future studies should focus on the interrelationships between latitude and gradients in nutrient concentration and conductivity. [ABSTRACT FROM AUTHOR]

The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated (centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen, and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from 94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH4 +, and PO4 3− removal rates of 80 ± 5 g C mr −3 day−1, 89 ± 5 g N mr −3 day−1, and 13 ± 3 g P mr −3 day−1, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L−1, N–NH4 + of 656 ± 37 mg L−1, P–PO4 3+ of 117 ± 19 mg L−1, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic biofilm (photosynthetic O2 and TOC/NH4 + diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated by the combination of high pH and high NH3 concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass generated during the pretreated swine slurry biodegradation). [ABSTRACT FROM AUTHOR]

Thirteen intensive pig farms and two activated sludge treatment plants for pig slurry in north-western Spain were studied from April 2005 to June 2006 in order to evaluate the presence of enteric pathogens (Cryptosporidium, Giardia and helminths) and the efficiency with which they were removed. These parasites were present on 53%, 7% and 38% of the farms studied, respectively, with concentrations of 104–105 oocysts per litre (/L) for Cryptosporidium, 103 cysts/L for Giardia and 102–103 eggs/L for helminths. The overall removal of parasites in the pig slurry treatment plants ranged from 86.7% to over 99.99%. The results revealed a constant reduction at each stage of the treatment system, with activated sludge processes being the most effective treatment in reducing pathogens in pig slurry, 78–81% for Cryptosporidium oocysts and over 99.9% for helminth eggs. A heat drying procedure for sludge removed 4.3log units of Cryptosporidium oocysts, demonstrating the excellent effectiveness of this treatment for reducing pathogens in sludge intended to be applied to land. [Copyright &y& Elsevier]

The influence of water retention time and depth variation on the macrophyte community in two small shallow lakes in the northwest of Spain was studied. One lake is periodically flooded and the other deeper lake, which is usually inundated, dries up sporadically. The influence of water regime and the spatial heterogeneity of the abiotic environment on diversity values and their temporal evolution are shown. Foreach lake, a model of horizontal arrangement of species is established. A differential arrangement of optima for dominant species was observed along the depth gradient. This arrangement remained constant intime. [ABSTRACT FROM AUTHOR]

The concentrations of N, P and C in the above-ground biomass of 14 dominant macrophyte species in shallow lakes in N.W. Spain were measured. The plants included macroalgae, aquatic (submerged and floating leaved) and emergent angiosperms. Significant differences among the species and among the groups of macrophytes were observed for the threenutrients. The macroalgae showed the lowest P (0.053% dry weight) and C (35.24% dry weight) content, whilst an impoverishment in N (1.38%dry weight) was observed in the emergent species. Only the macroalgae showed a strong association between N and P (r = 0.743, p<0.0001), reflecting an important biochemical connection in these species. A negative relation was observed between N and C (rs = -0.711,p<0.0001) as a result of the change pattern exhibited by these nutrients in the tissues of aquatic and emergent angiosperms. The existence of N limitation of growth of both angiosperm groups, with a contentbelow critical level, was deduced. P was established as the limitingfactor of all the macrophyte groups (N:P = 35:1), especially macroalgae, in which it was below the critical minimum. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the abundance and spatial dynamics of antibiotic-resistant fecal bacteria (Escherichia coli, total coliforms and Enterococcus spp.) were determined in water and sediment samples from a river impacted by both antibiotic production plant (APP) and urban wastewater treatment plant (WWTP) discharges. Agar dilution and disk diffusion methods were also used for antimicrobial susceptibility testing. Two antimicrobial agents, cephalexin (25μg/ml) and amoxicillin (50μg/ml), were evaluated using the agar dilution method for E. coli, total coliforms (TC) and Enterococcus spp., whereas the degree of sensitivity or resistance of E. coli isolates to penicillin (10U), ampicillin (10μg), doxycycline (30μg), tetracycline (30μg), erythromycin (15μg), azithromycin (15μg) and streptomycin (10μg) was performed using the disk diffusion method. Real-time PCR assays were used to determine the prevalence of three antibiotic-resistance genes (ARGs). The agar dilution method showed that most E. coli isolates and TC were resistant to amoxicillin, especially after receiving the APP discharges. Antibiotic resistances to amoxicillin and cephalexin were higher after the APP discharge point than after the WWTP effluent. The disk diffusion method revealed that 100% of bacterial isolates were resistant to penicillin and erythromycin. Multidrug-resistant bacteria were detected and showed a higher proportion at the WWTP discharge point than those in the APP. Highly multidrug-resistant bacteria (resistance to more than 4 antibiotics) were also detected, reaching mean values of 41.6% in water samples and 50.1% in sediments. The relative abundance of the bla TEM, bla CTX-M and bla SHV genes was higher in samples from the treatment plants than in those collected upstream from the discharges, especially for water samples collected at the APP discharge point. These results clearly demonstrate that both the APP and the WWTP contribute to the emergence and spread of antibiotic resistance in the environment. [Copyright &y& Elsevier]

Highlights: [•] Higher carbon removals in the open algal–bacterial biofilm due to stripping. [•] Similar nitrogen removals in enclosed and open algal–bacterial biofilm bioreactors. [•] Effective phosphorus removal only in the open algal–bacterial biofilm bioreactor. [•] Similar biomass composition regardless of the operational stage and photobioreactor. [•] Higher microalgae biodiversity in the open biofilm photobioreactor. [ABSTRACT FROM AUTHOR]

Abstract: Two conventional chemical coagulants (FeCl3 and Fe2(SO4)3) and five commercial polymeric flocculants (Drewfloc 447, Flocudex CS/5000, Flocusol CM/78, Chemifloc CV/300 and Chitosan) were comparatively evaluated for their ability to remove algal–bacterial biomass from the effluent of a photosynthetically oxygenated piggery wastewater biodegradation process. Chlorella sorokiniana, Scenedesmus obliquus, Chlorococcum sp. and a wild type Chlorella, in symbiosis with a bacterial consortium, were used as model algal–bacterial consortia. While the highest biomass removals (66–98%) for the ferric salts were achieved at concentrations of 150–250mgL−1, dosages of 25–50mgL−1 were required for the polymer flocculants to support comparable removal efficiencies. Process efficiency declined when the polymer flocculant was overdosed. Biomass concentration did not show a significant impact on flocculation within the concentration range tested. The high flocculant requirements herein recorded might be due to the competition of colloidal organic for the flocculants and the stationary phase conditions of biomass. [ABSTRACT FROM AUTHOR]

Abstract: Two green microalgae (Scenedesmus obliquus and Chlorella sorokiniana), one cyanobacterium (Spirulina platensis), one euglenophyt (Euglena viridis) and two microalgae consortia were evaluated for their ability to support carbon, nitrogen and phosphorous removal in symbiosis with activated sludge bacteria during the biodegradation of four and eight times diluted piggery wastewater in batch tests. C. sorokiniana and E. viridis were capable of supporting the biodegradation of four and eight times diluted wastewater. On the other hand, while S. obliquus and the consortia isolated from a swine manure stabilization pond were only able to grow in eight times diluted wastewater, S. platensis and the consortium isolated from a high rate algal pond treating swine manure were totally inhibited regardless of the dilution applied. TOC removal efficiencies (RE) ranging from 42% to 55% and NH4 +-RE from 21% to 39% were recorded in the tests exhibiting photosynthetic oxygenation. The similar oxygen production rates exhibited by the tested microalgae under autotrophic conditions (from 116 to 133mgO2 L−1 d−1) suggested that factors other than the photosynthetic oxygenation potential governed piggery wastewater biodegradation. Microalgal tolerance towards NH3 was hypothesized as the key selection criterion. Further studies in a continuous algal–bacterial photobioreactor inoculated with C. sorokiniana, S. obliquus and S. platensis showed that C. sorokiniana, the species showing the highest NH3-tolerance, rapidly outcompeted the rest of the microalgae during the biodegradation of eight times diluted wastewater, achieving TOC and NH4 +-RE comparable to those recorded in the batch biodegradation tests. [Copyright &y& Elsevier]

Abstract: The performance of two 464-L high rate algal ponds (HRAPs) treating 20- and 10-folds diluted swine manure at 10days of hydraulic residence time was evaluated under continental climatic conditions in Castilla y Leon (Spain) from January to October. Under optimum environmental conditions (from July to September), both HRAPs supported a stable and efficient carbon and nitrogen oxidation performance, with average COD and TKN removal efficiencies of 76±11% and 88±6%, respectively, and biomass productivities ranging from 21 to 28g/m2 d. Nitrification was identified as the main TKN removal mechanism at dissolved oxygen concentrations higher than 2mg/L (accounting for 80–86% of the TKN removed from January to May and for 54% from July to September). On the other hand, empirical evidences of a simultaneous nitrification–denitrification process were found at dissolved oxygen concentrations lower than 0.5mg/L (high organic loading rates). However, despite the achievement of excellent COD and nitrogen oxidation performance, phosphorous removal efficiencies lower than 10% were recorded in both HRAPs probably due to the high buffer capacity of the piggery wastewater treated (absence of abiotic pH-mediated precipitation). Finally, a detailed monitorization of the dynamics of microalgae population revealed that the combination of moderate temperatures/solar irradiances and high organic loading rates, prevailing during late spring and summer, supported higher microalgae diversities than those found during winter conditions. [Copyright &y& Elsevier]

Two green microalgae (Scenedesmus obliquus and Chlorella sorokiniana), one cyanobacterium (Spirulina platensis), one euglenophyt (Euglena viridis) and two microalgae consortia were evaluated for their ability to support carbon, nitrogen and phosphorous removal in symbiosis with activated sludge bacteria during the biodegradation of four and eight times diluted piggery wastewater in batch tests. C. sorokiniana and E. viridis were capable of supporting the biodegradation of four and eight times diluted wastewater. On the other hand, while S. obliquus and the consortia isolated from a swine manure stabilization pond were only able to grow in eight times diluted wastewater, S. platensis and the consortium isolated from a high rate algal pond treating swine manure were totally inhibited regardless of the dilution applied. TOC removal efficiencies (RE) ranging from 42% to 55% and NH(4)(+)-RE from 21% to 39% were recorded in the tests exhibiting photosynthetic oxygenation. The similar oxygen production rates exhibited by the tested microalgae under autotrophic conditions (from 116 to 133mgO(2)L(-1)d(-1)) suggested that factors other than the photosynthetic oxygenation potential governed piggery wastewater biodegradation. Microalgal tolerance towards NH(3) was hypothesized as the key selection criterion. Further studies in a continuous algal-bacterial photobioreactor inoculated with C. sorokiniana, S. obliquus and S. platensis showed that C. sorokiniana, the species showing the highest NH(3)-tolerance, rapidly outcompeted the rest of the microalgae during the biodegradation of eight times diluted wastewater, achieving TOC and NH(4)(+)-RE comparable to those recorded in the batch biodegradation tests., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)