Urban wastewater treatment by seven species of microalgae and an algal bloom: Biomass production, N and P removal kinetics and harvestability

This study evaluates the capacity of seven species and a Bloom of microalgae to grow in urban wastewater. Nutrient removal kinetics and biomass harvesting by means of centrifugation and coagulation–flocculation-sedimentation have been also tested. Results show that the best biomass productivities ranged from between 118 and 108 mgSS L−1 d−1 for the Bloom (Bl) and Scenedesmus obliquus (Sco). Regarding nutrient removal, microalgae were able to remove the total dissolved phosphorus and nitrogen concentrations by more than 80% and 87% respectively, depending on the species tested. The final total dissolved concentration of nitrogen and phosphorus in the culture media complies with the European Commission Directive 98/15/CE on urban wastewater treatment. Regarding harvesting, the results of coagulation–flocculation sedimentation using a 60 mg L−1 dose of Ferric chloride were similar between species, exceeding the biomass removal efficiency by more than 90%. The results of centrifugation (time required to remove 90% of solids at 1000 rpm) were not similar between species, with the shortest time being 2.9 min for Sco, followed by the bloom (7.25 min). An overall analysis suggested that the natural bloom and Scenedesmus obliquus seem to be the best candidates to grow in pre-treated wastewater, according to their biomass production, nutrient removal capability and harvestability

Sources, transport and fate of PAHs in sediments and superficial water of a chronically polluted semi-enclosed body of seawater: linking of compartments.

This paper describes a study of the occurrence, levels and temporal evolution of PAHs in a bay characterized by persistent chronic impacts. A total of 40 samples, 20 of sediment and 20 of water, were taken at each of five different stations, in four sampling campaigns. Analyses of pollutants have been made using GC-MS. Results indicate that in a coastal environment subjected to chronic pollution by pyrolytic PAHs, episodes of petrogenic pollution, like oil-spills, can be identified by the combination of different source ratios. Results also indicate that, in the study area, PAHs are transported from superficial water to sediment. This conclusion is based on the degree of coincidence found in the presence/absence of individual PAHs in both compartments and in their petrogenic/pyrolytic nature, the positive sedimentation rate in the study area, together with the performance of the analyses of unfiltered water and the distribution of sources of PAHs found

Cinética de consumo de nutrientes y crecimiento de un bloom de microalgas en un fotobiorreactor High Rate Algae Pond (HRAP)

In the present work, a bloom of microalgae was cultured in a pilotscale high rate algae pond (HRAP) photobioreactor with a volume of 450 l. This was performed in batch with synthetic media under natural light and temperature conditions. The objective was to predict the kinetics of biomass growth, nitrogen and phosphorus removal, and the evolution of the biomass content in these nutrients. The results show a reduction in nitrogen and phosphorus contents of over 80% with synthetic wastewater and that the model was useful to predict nutrient uptake by microalgae which, along with experimental data related to nutrient contents of biomass, indicates the existence of other processes that compete with microalgae in the removal of nutrients in a photobioreactor

The potential of different marine microalgae species to recycle nutrients from recirculating aquaculture systems (RAS) fish farms and produce feed additives

This study researched the use of six microalgae species (N. gaditana, P. lutheri, I. galbana, T. chuii, P. tricornutum and C. gracilis) and a bloom to treat effluent from a marine fish farm and produce quality biomass. More specifically, simulated water from a recirculating aquaculture system (RAS) was used. Microalgae culture was carried out under controlled conditions using 18 L bubble column photoreactors under batch and semi-continuous operation. The main parameters analysed were micronutritional requirements, biomass productivity, nutrient removal rate (nitrogen and phosphorus), biomass composition, and quality. Also, based on the results obtained, a quantitative classification of the microalgae was carried out. The results showed that all microalgae required at least trace metals. In certain species, the addition of vitamins was also required for viable cultivation. In the case of biomass productivity under batch operation, values were between 67 mg L−1 d−1 and 7 mg L−1 d−1 using T. chuii and C. gracilis, respectively, and between 71 mg L−1 d−1 and 9 mg L−1 d−1 using T. chuii and N. gaditana under semi-continuous operation. In the case of total dissolved phosphorus removal, no differences were found between species, reaching in all cases final concentrations <0.01 mg L−1. Total dissolved nitrogen removal rate varied between species and operating conditions, being the highest obtained using T. chuii under semi-continuous operation (12.6 mg L−1 d−1) and the lowest with C. gracilis batch operation (0.15 mg L−1 d−1). Biomass composition in terms of protein and lipids varied between species and operating conditions, but quality in terms of amino acids and fatty acids profile remained homogeneous in all cases. Finally, according to the developed score methodology, I. galbana was the microalgae with the highest biomass production score, while T. chuii was for wastewater treatment. © 2021This work was carried out within the SUNRAS Project ?Sustainable and Efficient Management of Marine Aquaculture Effluents using Solar Technologies? (N? AGL2016-80507-R; Plan Nacional de I+D+i 2013?2016) funded by Ministry of Economy and Competitiveness, Government of Spain. This study was also supported by a Personal Investigador en Formaci?n (PIF) contract (Ref. UCA/REC01VI/2017) funded by Universidad de C?diz. We also would like to acknowledge the technicians of Servicio Central de Investigaci?n en Cultivos Marinos at the Faculty of Marine and Environmental Science (Universidad de C?diz) and Centro Tecnol?gico de Acuicultura de Andaluc?a (CTAQUA) for their support

Microbial indicators of faecal contamination in waters and sediments of beach bathing zones

This study presents the results obtained of the microbial characterization of waters and sediments of 18 coastal bathing zones of the south-western coast of the Iberian Peninsula. To make this characterization, two indicators of faecal contamination have been selected: faecal coliforms (FC) and Clostridium perfringens (CP). The results show that low concentrations of FC and CP in water not necessarily implies that their concentration in sediment and elutriates has to be low as well. The highest concentrations were found in locations close to the mouth of rivers, and in beaches of low energy and hence low water renewal, and high accumulation of fine sediments. The concentrations of FC were lower than those obtained for CP in most of the sampling locations. Although quality standards for bathing waters do not take the parameter CP into account, it has been demonstrated that it should be a good indicator of faecal contamination

Ecotoxicity and biodegradability of an alkyl ethoxysulphate surfactant in coastal waters.

Alkyl ethoxysulphates (AES) are anionic surfactants widely used in numerous commercial and industrial applications. In spite of the high AES volume consumption a few data concerning the occurrence, fate and effects of AES in marine environments are reported in literature. The objective of this study is to evaluate the biodegradability and toxicity of AES in pristine sea water. Ultimate biodegradation was studied according to the guideline 835.3160 “Biodegradability in sea water” proposed by the United States Environmental Protection Agency (USEPA). Acute toxicity of AES was studied to the microalgae Nannochloropsis gaditana, Isochrysis galbana, Chaetoceros gracilis, Dunaliella salina and Tetraselmis chuii and the invertebrate Artemia franciscana, using culture growth inhibition and death, respectively, as effect criteria. During the degradative process two different stages were observed, which were better described with the first order and logistic kinetic models, respectively. Lag times were 3.3 (stage A) and 26.5 (stage B) days whereas half-lives were 18.6 (stage A) and 49.8 (stage B) days. AES inhibited the microalgae growth, with 96-h EC50 values ranging from 4.68 g L− 1 for D. salina to 24.02 mg L− 1 for I. galbana. Mean 48- and 72-h LC50 values for A. franciscana were 38.30 and 23.92 mg L− 1, respectively. The results indicate an extensive biodegradability of AES in sea water, although at a very slow rate. Acute toxicity was highly dependent on the species tested, being the green alga D. salina the most affected organism. The present study provides relevant data concerning the biodegradability and adverse effects of an AES surfactant on marine organisms, which are useful to establish water quality criteria in a regulatory framework

Effect of the test media and toxicity of LAS on the growth of Isochrysis galbana.

In this paper, the toxicity of linear alkylbenzene sulfonate (LAS) was evaluated in the marine microalga Isochrysis galbana using data of growth inhibition toxicity tests at 96-h exposure time. Toxicity was examined in standard conditions and by means of the modification of two variables of the test media: (1) the dilution water and (2) the content of nutrients in the test medium. For this purpose, a total of 10 toxicity test were designed: five dilution waters, four natural marine waters and one synthetic seawater; each in two different nutritive conditions, saturated nutrient concentration (SC) by the addition of modified f/2 nutritive medium, and natural nutrient concentration (NC), i.e., without the addition of f/2. At threshold toxicity levels, the dilution waters used in the test and the nutrient concentrations did not affect the toxicity of LAS. At IC50 concentrations, the toxicity of LAS is influenced by both variables: under SC conditions, the toxic effect of LAS diminishes, obtaining in all the tests IC50 > 10 mg/L LAS. Under NC conditions, IC50 concentrations ranging between 3.15 and 9.26 mg/L LAS have been obtained

Microalgae biotechnology for simultaneous water treatment and feed ingredient production in aquaculture br

The use of Tetraselmis chui to produce sole feed ingredient and the recovery of nutrients from a recirculating aquaculture system (RAS) aquaculture facility was studied. The microalga was cultured in a pilot-scale (6 m3) outdoor raceway reactor located in a sole production plant. First, the growth of the microalgae, the addition of phosphorus and the quality of the resulting water were studied. It was possible to cultivate in semi-continuous mode T. chui using the purge stream of a RAS, obtaining productivities of 15 mg L1 d1, and reaching 36 mg L1 d1 when phosphorus was added. In terms of water quality of the effluent, the pollutants concentration were below discharge limits (suspended solids and total dissolved nitrogen, phosphorus and carbon) -directive 91/ 271/EEC. In the case of Vibrio sp., the concentration in the culture water at the end of the experiments remained below typical environmental concentrations (10 % microalgae

Removal of emerging pollutants in conventional and microalgae based biotechnology urban wastewater treatment plants

Wastewater treatment plants (WWTPs) reduce portion of the input of pharmaceuticals in aquatic systems, but there is no data available about the elimination of emerging contaminants with microalgae technology. The aim of this work was to determine the average mass flows and concentrations of pharmaceuticals in influents and effluents from two sewages treatment plants using conventional and microalgae based biotechnologies and to compare the removal of pharmaceuticals using both depuration technologies. Only between 20 to 60% of five pharmaceuticals groups is reduce in both WWTP using conventional technologies consisting of a pretreatment, primary settling and secondary treatment by aerobic biological reactor. Using microalgae based biotechnologies efficiency of removal pharmaceuticals is higher than conventional technologies and it increase by using DAF (Dissolve Air Flotation) technology to separate algae biomass

Cinéticas de crecimiento y consumo de nutrientes de microalgas en aguas residuales urbanas con diferentes niveles de tratamiento

El objetivo principal de este trabajo ha sido el estudio de la velocidad de crecimiento y de consumo de nitrógeno y fósforo de un bloom de microalgas cultivadas en aguas residuales urbanas con diferente nivel y tipología de tratamiento. Para ello se han cultivado las microalgas por duplicado en discontinuo bajo condiciones controladas de temperatura, luz y aireación, en cuatro medios de ensayo, consistentes en cuatro aguas residuales: (1) salida de pretratamiento; (2) efluente de decantación secundaria; (3) efluente de un reactor anaerobio de flujo ascendente denominado UASB (Upflow Anaerobic Sludge Blanket), y finalmente, (4) mezcla de efluente del UASB y agua de secundario, todas de la misma estación depuradora de aguas residuales urbanas. La modelización cinética para el análisis de resultados con los modelos de Verhulst y el Photobiotreatment model indica una evolución temporal diferente de la concentración de biomasa, N y P total disuelto, respectivamente, en los diferentes medios de ensayo. La productividad es mayor en los ensayos con agua procedente del biorreactor UASB (0.094 g SS l-1 d-1). En este medio de cultivo, la velocidad de eliminación del nitrógeno no presenta diferencia con el resto de aguas residuales utilizadas en el ensayo, mientras que en el caso del fósforo, la eliminación es la menor de entre todos los medios estudiados