Humbert Salvadó

Determination of organic loading rate of activated sludge plants based on protozoan analysis

Abstract Variations in the structure of the protozoan community living in activated sludge were studied in relation with the organic loading rate. 84 samples were taken over a 14 month period. Sludge and wastewaters were subjected to microscopic and physico-chemical analyses. The organic loading rate corresponding to each microscopic count was determined as the average of the values calculated for the 2 days previous to the count. Ciliate species abundance and specific diversity of ciliates were strongly related to the organic loading rate. Data were compared to three other facilities. Ciliate diversity decreased as the organic loading rate increased. This relationship could be modified if solids in suspension surpassed 4000 MLVSS mg/l or if volumetric loading rates were higher than 800 g BOD 5 /m 3 day. An easy, fast diagnostic test to estimate the organic loading rate in less than 5 days and to obtain information on plant performance is proposed.

FORAMINIFERAL COLONIZATION ON ARTIFICIAL SEAGRASS LEAVES

Colonization of seagrass leaves was studied using artificial ribbon-like substrates. The study was carried out in a seagrass ( Posidonia oceanica (L.) Delile) meadow off the Medes Islands (NW Mediterranean). Artificial leaves of different colors and textures were immersed at two depths (5 and 13 m), and retrieved after 3 and 6 months; epiphytic foraminifera were identified and counted, and the results were compared with those obtained from natural leaves. Although some differences were found in the colonization of the various types of artificial leaf (e.g., smooth, green leaves with float bladder had the highest number of individuals and species) ANOVA and cluster analyses revealed that the type of substrate did not significantly affect the colonization by foraminifera; the main sources of variability were mainly seasonality and, to a minor extent, water depth. Thus, the dominant species were the same in both natural and artificial leaves. The calcareous perforated shells and the trochospiral morphotype were the most abundant, and the dominant biological types were groups B and C, i.e., temporarily or permanently mobile species.

Assessment of plausible bioindicators for plant performance in advanced wastewater treatment systems

Three full-scale advanced biological systems for nitrogen removal showing different efficiencies were assessed during one year, to investigate the protist communities supported in these wastewater treatment plants (WWTP). The main goal of this research was to explore the differences of these communities from those observed in conventional activated sludge systems. The final objective was to provide background support for the proposal of bioindicators in this type of biological systems, where scarce information was available until now, since only conventional systems had been previously studied from this point of view. Results obtained indicate that, in fact, protist population density and diversity in advanced systems for N-elimination are quite different from other wastewater systems studied before. A statistical approach through multivariate analysis was developed to search for association between protist species and physical-chemical system performance, and specifically N-removal efficiencies. The original hypothesis proposing that previous indicators from conventional systems are not adequate in advanced N-removal mechanisms was proved to be correct. Efficient processes on N-removal, despite what it had been usually found in conventional systems, show important flagellate and amoeba populations and these populations tend to reduce their abundances as nitrogen removal performance decreases (moderate to low). Ciliates are however less abundant in these N-removal efficient systems. Certain groups and genera of protist such as flagellates and small amoebae are thus proposed as indicative of high performance N-removal, while in this case the appearance of certain ciliates were indicative of low performance on N- or high organic matter removal (as COD) efficiencies.

Outbreaks of Ichthyophthirius multifiliis in Redtail Barbs Barbus haasi in a Mediterranean Stream during Drought

In 2008, inland waterways in Catalonia (northeast Iberian Peninsula, Spain) experienced one of the worst droughts recorded in this region in recent decades. During this period, an epizootic of Ichthyophthirius multifiliis was detected for the first time in a Mediterranean stream, with 21% prevalence in a population of redtail barbs Barbus haasi. Environmental features and the fish population in this stream were compared during 2007-2009. Fish density and the average fish size were reduced significantly after the outbreak of I. multifiliis in this population. During 2008, parasitized fish were significantly larger than nonparasitized fish. In addition, a significant, positive correlation was found between parasite load and fish size. The origin of I. multifiliis is unknown, but an introduced species detected in April 2007 may have carried it. The combination of stress to the redtail barbs due to suboptimal conditions and favorable environmental conditions for parasite multiplication (e.g., suitable water temperature and low water flow) could have enhanced fish susceptibility to the parasite in April 2008. Further studies are needed to establish the incidence of freshwater fish diseases in Mediterranean watersheds, and water management policies should be reviewed to improve the conservation of native fish fauna.

Effect of mean cellular retention time on ciliated protozoan populations in urban wastewater treatment plants based on a proposed model

Abstract The succession of the microbial population depending on mean cellular retention time (MCRT) in activated sludge wastewater treatment plants is studied. Three facilities were studied for a 1 year period. Microorganisms (protozoa, small metazoa and filamentous microorganisms) were counted using an optical microscope, specifically determining ciliated protozoa. A mathematical model is proposed for MCRT and the comparison between the experimental results and those predicted by the proposed model reveals that there is a difference between: (1) the succession of protozoa during the start up of a plant and (2) the succession due to variations in MCRT variation in the normal functioning of the plant. Although variations in protozoan population depend on mean cellular retention time in the short term (less than a week) they also depend on the protozoan species present. In the long run (several weeks), ciliated protozoan community coincides according to the MCRT in the three plants studied. The characterization of the fauna for each range of MCRT on the basis of the proposed model allows plant operation to be monitored by microscopic examination.

Microfauna communities as performance indicators for an A/O Shortcut Biological Nitrogen Removal moving-bed biofilm reactor

The microfauna communities present in the mixed liquor and biofilm of an Anoxic/Oxic Shortcut Biofilm Nitrogen Removal moving-bed biofilm process were characterised in order to optimise process control through the use of bioindicators. The system operated at high ammonium concentrations, with an average of 588 ± 220 mg N-NH4(+) L(-1) in the influent, 161 ± 80 mg L(-1) in the anoxic reactor and 74 ± 71.2 mg L(-1) in the aerobic reactor. Up to 20 different taxa were identified, including ciliates (4), flagellates (11), amoebae (4) and nematodes (1). Compared to conventional wastewater treatment processes (WWTPs), this process can be defined as a flagellates-predominant system with a low diversity of ciliates. Flagellates were mainly dominant in the mixed liquor, demonstrating high tolerance to ammonium and the capacity for survival over a long time under anoxic conditions. The data obtained provide interesting values of maximum and minimum tolerance ranges to ammonium, nitrates and nitrites for the ciliate species Cyclidium glaucoma, Colpoda ecaudata, Vorticella microstoma-complex and Epistylis cf. rotans. The last of these was the only ciliate species that presented a constant and abundant population, almost exclusively in the aerobic biofilm. Epistylis cf. rotans dynamics showed a high negative correlation with ammonium variations and a positive correlation with ammonium removal efficiency. Hence, the results indicate that Epistylis cf. rotans is a good bioindicator of the nitrification process in this system. The study of protozoan communities in unexplored WWTPs sheds light on species ecology and their role under conditions that have been little studied in WWTPs, and could offer new biological management tools.

The use of rotifers for limiting filamentous bacteria Type 021N, a bacteria causing activated sludge bulking

The excessive growth of filamentous bacteria and the resultant bulking of activated sludge constitute a serious problem in numerous wastewater treatment plants. Lecane inermis rotifers were previously shown to be capable of reducing the abundance of Microthrix parvicella and Nostocoida limicola in activated sludge. In the present study, the effectiveness of four Lecane clones in reducing the abundance of Type 021N filamentous bacteria was investigated. Three independent experiments were carried out on activated sludge from three different treatment plants. We found that Lecane rotifers are efficient consumers of Type 021N filaments.

Longevity and effects of temperature on the viability and polar-tube extrusion of spores of Glugea stephani, a microsporidian parasite of commercial flatfish.

Abstract Food contamination with respect to microsporidiosis in humans (associated with acquired immunodeficiency syndrome) and in marine fish farming deserves particular attention. For the first time, a study on the longevity and resistance to both heat and freezing of the spores of a vertebrate microsporidian, Glugea stephani, parasitizing a commercial flatfish was carried out. As judged on the basis of determinations of the extrusion rate, the resistance of the spores to temperature stress was remarkable. The extrusion rate, which can be directly related to infectivity, was always lower than the viability (membrane integrity). It should be pointed out that neither heat (60° C for 30 min) nor freezing (−19° C for 24 h) caused a complete reduction in the extrusion rate or viability. Consequently, the ingestion of poorly cooked or raw fish (even if previously frozen) represents a danger for aquaculture and, probably, for immunodepressed patients.

Tetramicra brevifilum (Matthews & Matthews, 1980) (Microsporida: Tetramicriidae) in a new fish host, Lophius budegassa (Spinola, 1807) in Spain

Tetramicra brevifilum, a microsporidian parasite of Scophthalmus maximus, was found in Lophius budegassa for the first time. This parasite was detected in 5 of 199 hosts captured in the coastal waters of Barcelona (Northwest Mediterranean), which enlarges the geographic distribution of this microsporidian. Affected fish did not show any external sign of disease, and cysts of T. brevifilum were found associated with the body musculature but were easily differentiated from those of Spraguea lophii, another microsporidian present in this host. A case of simultaneous infection by both T. brevifilum and S. lophii was found.

Comparative Study of Microsporidian Spores by Flow Cytometric Analysis

ABSTRACT. Spore suspensions of microsporidian parasites of fish (Microsporidium ovoideum, Glugea stephani, Glugea atherinae and Spraguea lophii) have been analyzed by flow cytometry. Spore nuclei were dyed either by propidium iodide or bis‐benzimide (Hoechst 33342). By observation of forward light scatter and fluorescence the four species could be distinguished and the mono‐ and diplokaryotic populations of S. lophii identified. Staining of DNA by bis‐benzimide was better and easier than propidium iodide. Forward light scatter and fluorescence values were characteristic of each species and remained unchanged throughout the year, so flow cytometry can be used for distinction of spores of some microsporidian parasites once their flow cytometric parameters are known. However, special care has to be taken in tool calibration and material preparation for analysis because of the high precision of the technique.