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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]

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]

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.)