M1 and M2 mAChRs activate PDK1 and regulate PKC ßI and ε and the exocytotic apparatus at the NMJ.

Neuromuscular junctions (NMJ) regulate cholinergic exocytosis through the M1 and M2 muscarinic acetylcholine autoreceptors (mAChR), involving the crosstalk between receptors and downstream pathways. Protein kinase C (PKC) regulates neurotransmission but how it associates with the mAChRs remains unknown. Here, we investigate whether mAChRs recruit the classical PKCßI and the novel PKCε isoforms and modulate their priming by PDK1, translocation and activity on neurosecretion targets. We show that each M1 and M2 mAChR activates the master kinase PDK1 and promotes a particular priming of the presynaptic PKCßI and ε isoforms. M1 recruits both primed-PKCs to the membrane and promotes Munc18-1, SNAP-25, and MARCKS phosphorylation. In contrast, M2 downregulates PKCε through a PKA-dependent pathway, which inhibits Munc18-1 synthesis and PKC phosphorylation. In summary, our results discover a co-dependent balance between muscarinic autoreceptors which orchestrates the presynaptic PKC and their action on ACh release SNARE-SM mechanism. Altogether, this molecular signaling explains previous functional studies at the NMJ and guide toward potential therapeutic targets.

Effect of long residence time and high temperature over anaerobic biodegradation of Scenedesmus microalgae grown in wastewater.

Anaerobic digestion of indigenous Scenedesmus spp. microalgae was studied in continuous lab-scale anaerobic reactors at different temperatures (35 °C and 55 °C), and sludge retention time - SRT (50 and 70 days). Mesophilic digestion was performed in a continuous stirred-tank reactor (CSTR) and in an anaerobic membrane bioreactor (AnMBR). Mesophilic CSTR operated at 50 days SRT only achieved 11.9% of anaerobic biodegradability whereas in the AnMBR at 70 days SRT and 50 days HRT reached 39.5%, which is even higher than the biodegradability achieved in the thermophilic CSTR at 50 days SRT (30.4%). Microbial analysis revealed a high abundance of cellulose-degraders in both reactors, AnMBR (mainly composed of 9.4% Bacteroidetes, 10.1% Chloroflexi, 8.0% Firmicutes and 13.2% Thermotogae) and thermophilic CSTR (dominated by 23.8% Chloroflexi and 12.9% Firmicutes). However, higher microbial diversity was found in the AnMBR compared to the thermophilic CSTR which is related to the SRT. since high SRT promoted low growth-rate microorganisms, increasing the hydrolytic potential of the system. These results present the membrane technology as a promising approach to revalue microalgal biomass, suggesting that microalgae biodegradability and consequently the methane production could be improved operating at higher SRT.

Influence of food waste addition over microbial communities in an Anaerobic Membrane Bioreactor plant treating urban wastewater.

Notorious changes in microbial communities were observed during and after the joint treatment of wastewater with Food Waste (FW) in an Anaerobic Membrane Bioreactor (AnMBR) plant. The microbial population was analysed by high-throughput sequencing of the 16S rRNA gene and dominance of Chloroflexi, Firmicutes, Synergistetes and Proteobacteria phyla was found. The relative abundance of these potential hydrolytic phyla increased as a higher fraction of FW was jointly treated. Moreover, whereas Specific Methanogenic Activity (SMA) rose from 10 to 51 mL CH4 g-1 VS, Methanosarcinales order increased from 34.0% over 80.0% of total Archaea, being Methanosaeta the dominant genus. The effect of FW over AnMBR biomass was observed during the whole experience, as methane production rose from 49.2 to 144.5 L CH4 · kg-1 influent COD. Furthermore, biomethanization potential was increased over 82% after the experience. AnMBR technology allows the established microbial community to remain in the bioreactor even after the addition of FW, improving the anaerobic digestion of urban wastewater.

Resource recovery from sulphate-rich sewage through an innovative anaerobic-based water resource recovery facility (WRRF).

This research work proposes an innovative water resource recovery facility (WRRF) for the recovery of energy, nutrients and reclaimed water from sewage, which represents a promising approach towards enhanced circular economy scenarios. To this aim, anaerobic technology, microalgae cultivation, and membrane technology were combined in a dedicated platform. The proposed platform produces a high-quality solid- and coliform-free effluent that can be directly discharged to receiving water bodies identified as sensitive areas. Specifically, the content of organic matter, nitrogen and phosphorus in the effluent was 45 mg COD·L-1, 14.9 mg N·L-1 and 0.5 mg P·L-1, respectively. Harvested solar energy and carbon dioxide biofixation in the form of microalgae biomass allowed remarkable methane yields (399 STP L CH4·kg-1 CODinf) to be achieved, equivalent to theoretical electricity productions of around 0.52 kWh per m3 of wastewater entering the WRRF. Furthermore, 26.6% of total nitrogen influent load was recovered as ammonium sulphate, while nitrogen and phosphorus were recovered in the biosolids produced (650 ± 77 mg N·L-1 and 121.0 ± 7.2 mg P·L-1).

Skewed Invariant Natural Killer T (iNKT) Cells, Impaired iNKT:B Cell Help and Decreased SAP Expression in Blood Lymphocytes from Patients with Common Variable Immunodeficiency.

Common variable immunodeficiency (CVID) is a syndrome with predominantly defective B cell function. However, abnormalities in the number and function of other lymphocyte subpopulations in peripheral blood (PB) have been described in most patients. We have analysed the distribution of iNKT cell subpopulations in the PB of CVID patients and the ability of these cells to provide in vitro cognate B cell help. The total of iNKT cells was reduced in the PB of CVID patients, especially CD4+, CD4-/CD8- and CCR5+/CXCR3+. These findings were associated with an enrichment of memory-like and a tendency towards a reduction in TNF-α-expressing effector iNKT cells in the peripheral blood mononuclear cells (PBMC) of CVID patients. Moreover, an accumulation of follicular helper iNKT cells in the PB of CVID patients was demonstrated. CVID αGalCer-pulsed iNKT cells are not able to induce autologous B cell proliferation although they do induce proliferation to healthy donor B cells. Interestingly, autologous and heterologous co-cultures did not differ in the amount of immunoglobulin secreted by B cells in vitro. Finally, reduced intracellular SAP expression in iNKT cells and other lymphocytes in the blood from CVID patients was observed. These results provide further insights into the immunological mechanisms underlying the iNKT cell defects and the potential targets to improve B cell help in CVID.

Identification and quantification of microbial populations in activated sludge and anaerobic digestion processes.

Eight different phenotypes were studied in an activated sludge process (AeR) and anaerobic digester (AnD) in a full-scale wastewater treatment plant by means of fluorescent in situ hybridization (FISH) and automated FISH quantification software. The phenotypes were ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, denitrifying bacteria, phosphate-accumulating organisms (PAO), glycogen-accumulating organisms (GAO), sulphate-reducing bacteria (SRB), methanotrophic bacteria and methanogenic archaea. Some findings were unexpected: (a) Presence of PAO, GAO and denitrifiers in the AeR possibly due to unexpected environmental conditions caused by oxygen deficiencies or its ability to survive aerobically; (b) presence of SRB in the AeR due to high sulphate content of wastewater intake and possibly also due to digested sludge being recycled back into the primary clarifier; (c) presence of methanogenic archaea in the AeR, which can be explained by the recirculation of digested sludge and its ability to survive periods of high oxygen levels; (d) presence of denitrifying bacteria in the AnD which cannot be fully explained because the nitrate level in the AnD was not measured. However, other authors reported the existence of denitrifiers in environments where nitrate or oxygen was not present suggesting that denitrifiers can survive in nitrate-free anaerobic environments by carrying out low-level fermentation; (e) the results of this paper are relevant because of the focus on the identification of nearly all the significant bacterial and archaeal groups of microorganisms with a known phenotype involved in the biological wastewater treatment.

Reliable method for assessing the COD mass balance of a submerged anaerobic membrane bioreactor (SAMBR) treating sulphate-rich municipal wastewater.

The anaerobic treatment of sulphate-rich wastewater causes sulphate reducing bacteria (SRB) and methanogenic archaea (MA) to compete for the available substrate. The outcome is lower methane yield coefficient and, therefore, a reduction in the energy recovery potential of the anaerobic treatment. Moreover, in order to assess the overall chemical oxygen demand (COD) balance, it is necessary to determine how much dissolved CH(4) is lost in the effluent. The aim of this study is to develop a detailed and reliable method for assessing the COD mass balance and, thereby, to establish a more precise methane yield coefficient for anaerobic systems treating sulphate-rich wastewaters. A submerged anaerobic membrane bioreactor (SAMBR) treating sulphate-rich municipal wastewater was operated at 33 °C for an experimental period of 90 d, resulting in a high COD removal (approximately 84%) with a methane-enriched biogas of 54 ± 15% v/v. The novelty of the proposed methodology is to take into account the sulphide oxidation during COD determination, the COD removed only by MA and the dissolved CH(4) lost with the effluent. The obtained biomethanation yield (333 L CH(4) kg(-1) COD(REM MA)) is close to the theoretical value, which confirms the reliability of the proposed method.

[Study of the impact of an assertive community program on the families of patients with severe mental disorders]. / Patients souffrant de troubles psychiatriques sévères suivis par une équipe mobile : impact sur leurs familles.

OBJECTIVES: Assertive Community Treatment (ACT) is known to have a positive impact on the number and length of inpatient stays. Yet, research is needed in order to help understand how ACT programs may ease off families' burden, e.g. in terms of economic expenditures. Indeed, many families with siblings suffering from chronic mental illness, who disengaged from psychiatric services, report needs related to ACT. This paper aims to describe the impact of a new ACT program in Geneva on patients and their families' burden. METHODS: Out of 91 patients consecutively treated by the ACT program for at least 3 months, 55 consented to participate in the research. Twenty-one allowed us to contact their families (out of 37 who had relatives in the area). Data were gathered on patients and families before and after a 6-month-follow-up. RESULTS: For the patients, after adjustment for the time spent during follow-up, most of the studied variables evolved favorably, particularly for their symptoms. At baseline, most of the family members felt overburdened by the financial cost (59.1%) related to their relatives with severe mental disorder and experienced inconvenience at having to give them assistance in daily life (68.2%) and to supervise them in daily activities (54.5%). Several variables evolved favorably during follow-up. Notably the best changes were observed for the inconvenience relating to assistance in daily life and relatives' emotional distress. Families of patients with delusional disorder featured less or no improvement during the ACT follow-up. The best correlate of improvement in familial burdens was improvement in patient's positives symptoms. Among those patients, being a female and suffering from a schizo-affective disorder was known to have had a higher impact on the number of interventions provided by families. DISCUSSION: ACT should be recommended for patients who feature a poor outcome when treated in other settings. In addition, our results suggest that their families can also improve considerably, particularly those confronted with patients with persistent and enduring disturbing behaviors related to positive symptoms which do not, however, warrant hospitalization. Clinicians should pay particular attention to patients suffering from delusional disorder and their families, as this disorder does not appear to be associated with improvement in family burdens. These data do not allow definitely disentangling whether the improvement of families' burden is directly related to ACT interventions with them, to the implementation of support by other structures (such as peer support groups) or to an indirect effect related to patients' improvement. To our knowledge no similar study on the effect of ACT on family burden exists. Hence, such research needs to be replicated in other areas with different clinical and cultural backgrounds.

Religious explanatory models in patients with psychosis: a three-year follow-up study.

BACKGROUND/AIMS: Spirituality and religiousness have been shown to be highly prevalent in patients with psychosis. Yet the influence of religious denomination as it affects coping methods and/or as an explanatory model for illness and treatment remains to be determined. This study aims (1) to investigate if religious denomination is associated with explanatory models, (2) to assess the evolution over time of these explanatory models, and (3) to examine the relationship between these explanatory models and the spiritual vision of treatment and adhesion to such treatment. SAMPLING AND METHODS: Of an initial cohort of 115 outpatients, 80% (n = 92) participated in a 3-year follow-up study. The evolution of their religious explanatory models was assessed in order to evaluate if religious denomination, as a meaning-making coping tool, is associated with the patients' explanatory models. Finally, we examined the relationship between these representations and the patients' spiritual visions of treatment and treatment adhesion. RESULTS: A spiritual vision of the illness (as part of an explanatory model) was more frequent in patients with psychosis for whom the subjective dimension of religion was important. However, there was no association between the patients' religious denomination and their spiritual vision of the illness. The analyses showed that the various contents of spiritual visions of illness were not positive or negative per se; instead, they depended on how this religious vision was integrated into the person's experience. Examining longitudinal aspects of coping showed that the spiritual vision sometimes changed, but was not associated with clinical or social outcome. CONCLUSIONS: For patients with psychosis, explanatory models frequently involve a religious component which is independent of denomination and likely to change over time. Clinicians should address this issue on a regular basis, by asking patients about their explanatory model before trying to build a bridge with the medical model.

Short-term effect of ammonia concentration and salinity on activity of ammonia oxidizing bacteria.

A continuously aerated SHARON (single reactor high activity ammonia removal over nitrite) system has been operated to achieve partial nitritation. Two sets of batch experiments were carried out to study the effect of ammonia concentration and salinity on the activity of ammonia-oxidizing bacteria (AOB). Activity of AOB raised as free ammonia concentration was increased reaching its maximum value at 4.5 mg NH3-N l(-1). The half saturation constant for free ammonia was determined (K(NH3)=0.32 mg NH3-N l(-1)). Activity decreased at TAN (total ammonium-nitrogen) concentration over 2,000 mg NH4-N l(-1). No free ammonia inhibition was detected. The effect of salinity was studied by adding different concentrations of different salts to the biomass. No significant differences were observed between the experiments carried out with a salt containing or not containing NH4. These results support that AOB are inhibited by salinity, not by free ammonia. A mathematical expression to represent this inhibition is proposed. To compare substrate affinity and salinity inhibitory effect on different AOB populations, similar experiments were carried out with biomass from a biological nutrient removal pilot plant. The AOB activity reached its maximum value at 0.008 mg NH3-N l(-1) and decreased at TAN concentration over 400 mg NH4-N l(-1). These differences can be explained by the different AOB predominating species: Nitrosomonas europaea and N. eutropha in the SHARON biomass and Nitrosomonas oligotropha in the pilot plant.

Unveiling microbial structures during raw microalgae digestion and co-digestion with primary sludge to produce biogas using semi-continuous AnMBR systems.

Methane production from microalgae can be enhanced through anaerobic co-digestion with carbon-rich substrates and thus mitigate the inhibition risk associated with its low C:N ratio. Acclimated microbial communities for microalgae disruption can be used as a source of natural enzymes in bioenergy production. However, co-substrates with a certain microbial diversity such as primary sludge might shift the microbial structure. Substrates were generated in a Water Resource Recovery Facility (WRRF) and combined as follows: Scenedesmus or Chlorella digestion and microalgae co-digestion with primary sludge. The study was performed using two lab-scale Anaerobic Membrane Bioreactors (AnMBR). During three years, different feedstocks scenarios for methane production were evaluated with a special focus on the microbial diversity of the AnMBR. 57% of the population was shared between the different feedstock scenarios, revealing the importance of Anaerolineaceae members besides Smithella and Methanosaeta genera. The addition of primary sludge enhanced the microbial diversity of the system during both Chlorella and Scenedesmus co-digestion and promoted different microbial structures. Aceticlastic methanogen Methanosaeta was dominant in all the feedstock scenarios. A more remarkable role of syntrophic fatty acid degraders (Smithella, Syntrophobacteraceae) was observed during co-digestion when only microalgae were digested. However, no significant changes were observed in the microbial composition during anaerobic microalgae digestion when feeding only Chlorella or Scenedesmus. This is the first work revealing the composition of complex communities for semi-continuous bioenergy production from WRRF streams. The stability and maintenance of a microbial core over-time in semi-continuous AnMBRs is here shown supporting their future application in full-scale systems for raw microalgae digestion or co-digestion.

Orbital Magnetic Resonance Imaging to unmask giant cell arteritis. / Resonancia magnética orbitaria para desenmascarar arteritis de células gigantes.

Optic nerve enhancement is a sign seen in different disease states; however, perineural enhancement is less common. This article presents the case of a patient with bilateral amaurosis in whom the diagnosis of giant cell arteritis was suggested by perineural enhancement on orbital magnetic resonance imaging (MRI) and confirmed by biopsy of the temporal artery. The clinical presentation of giant cell arteritis is occasionally nonspecific; patients can have visual symptoms, even blindness if the branches of the ophthalmic artery are affected; in these cases, orbital MRI can be very useful for early diagnosis. Although the MRI findings are uncommon, distinct patterns of enhancement have been reported, the most characteristic of which is perineural enhancement. The pattern of optic nerve involvement is relatively unknown, but important because it orients the diagnosis of a disease that can lead to permanent blindness.

Improving membrane photobioreactor performance by reducing light path: operating conditions and key performance indicators.

Microalgae cultivation has been receiving increasing interest in wastewater remediation due to their ability to assimilate nutrients present in wastewater streams. In this respect, cultivating microalgae in membrane photobioreactors (MPBRs) allows decoupling the solid retention time (SRT) from the hydraulic retention time (HRT), which enables to increase the nutrient load to the photobioreactors (PBRs) while avoiding the wash out of the microalgae biomass. The reduction of the PBR light path from 25 to 10 cm increased the nitrogen and phosphorus recovery rates, microalgae biomass productivity and photosynthetic efficiency by 150, 103, 194 and 67%, respectively.The areal biomass productivity (aBP) also increased when the light path was reduced, reflecting the better use of light in the 10-cm MPBR plant. The capital and operating operational expenditures (CAPEX and OPEX) of the 10-cm MPBR plant were also reduced by 27 and 49%, respectively. Discharge limits were met when the 10-cm MPBR plant was operated at SRTs of 3-4.5 d and HRTs of 1.25-1.5 d. At these SRT/HRT ranges, the process could be operated without a high fouling propensity with gross permeate flux (J20) of 15 LMH and specific gas demand (SGDp) between 16 and 20 Nm3air·m-3permeate, which highlights the potential of membrane filtration in MPBRs. When the continuous operation of the MPBR plant was evaluated, an optical density of 680 nm (OD680) and soluble chemical oxygen demand (sCOD) were found to be good indicators of microalgae cell and algal organic matter (AOM) concentrations, while dissolved oxygen appeared to be directly related to MPBR performance. Nitrite and nitrate (NOx) concentration and the soluble chemical oxygen demand:volatile suspended solids ratio (sCOD:VSS) were used as indicators of nitrifying bacteria activity and the stress on the culture, respectively. These parameters were inversely related to nitrogen recovery rates and biomass productivity and could thus help to prevent possible culture deterioration.

Nitrite inhibition of microalgae induced by the competition between microalgae and nitrifying bacteria.

Outdoor microalgae cultivation systems treating anaerobic membrane bioreactor (AnMBR) effluents usually present ammonium oxidising bacteria (AOB) competition with microalgae for ammonium uptake, which can cause nitrite accumulation. In literature, nitrite effects over microalgae have shown controversial results. The present study evaluates the nitrite inhibition role in a microalgae-nitrifying bacteria culture. For this purpose, pilot- and lab-scale assays were carried out. During the continuous outdoor operation of the membrane photobioreactor (MPBR) plant, biomass retention time (BRT) of 2 d favoured AOB activity, which caused nitrite accumulation. This nitrite was confirmed to inhibit microalgae performance. Specifically, continuous 5-d lab-scale assays showed a reduction in the nitrogen recovery efficiency by 32, 42 and 80% when nitrite concentration in the culture accounted for 5, 10 and 20 mg N·L-1, respectively. On the contrary, short 30-min exposure to nitrite showed no significant differences in the photosynthetic activity of microalgae under nitrite concentrations of 0, 5, 10 and 20 mg N·L-1. On the other hand, when the MPBR plant was operated at 2.5-d BRT, the nitrite concentration was reduced to negligible values due to increasing activity of microalgae and nitrite oxidising bacteria (NOB). This allowed obtaining maximum MPBR performance; i.e. nitrogen recovery rate (NRR) and biomass productivity of 19.7 ± 3.3 mg N·L-1·d-1 and 139 ± 35 mg VSS·L-1·d-1, respectively; while nitrification rate (NOxR) reached the lowest value (13.5 ± 3.4 mg N·L-1·d-1). Long BRT of 4.5 d favoured NOB growth, avoiding nitrite inhibition. However, it implied a decrease in microalgae growth and the accumulation of nitrate in the MPBR effluent. Hence, it seems that optimum BRT has to be within the range 2-4.5 d in order to favour microalgae growth with respect to AOB and NOB.

Increasing self-esteem: efficacy of a group intervention for individuals with severe mental disorders.

BACKGROUND: Individuals with psychosis are known to have a lower self-esteem compared to the general population, in part because of social stigma, paternalistic care, long periods of institutionalization and negative family interactions. This study aimed at assessing the efficacy of a self-esteem enhancement program for individuals with severe mental illness and at analyzing the results in their European context. METHOD: A randomized cross-over study including 54 outpatients with a diagnosis of schizophrenia from Geneva, Switzerland, was conducted. Twenty-four were recruited from an outpatient facility receiving traditional psychiatric care whereas 30 came from an outpatient facility with case-management care. Psychosocial, diagnostic and symptom measures were taken for all the subjects before treatment, after treatment, and at 3-months' follow-up. RESULTS: Results indicated significant positive self-esteem module effects on self-esteem, self-assertion, active coping strategies and symptom for the participants receiving case-management care. Results were not significant for those receiving traditional care. However, 71% of all participants expressed satisfaction with the module. CONCLUSION: Individuals with schizophrenia appear to be benefit from the effects of the self-esteem module, particularly when they are involved in a rehabilitation program and followed by a case manager who liaises with the other partners of the multidisciplinary team. This encourages reconsidering the interventions' format and setting in order to ensure lasting effects on the environment and in turn on coping, self-esteem and overall empowerment.

[Long-term psychiatric consequences of carbon monoxide poisoning: a case report and literature review]. / Intoxication au monoxyde de carbone: quelles séquelles neuropsychiatriques? A propos d'un cas clinique et revue de la littérature.

Carbon monoxide intoxication (COI) can result in severe neuropsychiatric lesions that are however granted little attention in literature. Following the description of affective and neurological symptoms in a 37-year-old female patient five years following COI, we will review, across the literature (Medline 1974--2006), the long-term neuropsychiatric consequences, etiopathogenic hypotheses, prognoses and treatments to apply. Subjective symptoms are reported by the quasi-totality of patients for over more than 30 years following COI. More than half of patients are diagnosed as suffering from cognitive impairments and other neurological symptoms after years following COI. Affective disorders are observed in almost three-fourths of patients and personality disorders in more than half. Numerous cerebral lesions and perfusion disorders can be observed through IRM, PET scan and SPECT and related to the clinical symptomatology of the patient. COI may constitute a risk factor in the waking of long-term neuropsychiatric disorders in a context of environmental and neurobiological complex factor interaction. A close follow-up must be envisaged with neuropsychiatric assessments and regular neuroimagery in order to adapt at best therapeutic interventions to the patient's clinical status. First and foremost prevention and education remain the key solution to the reduction of morbidity and mortality of COI.

[Sodium intoxication with fatal outcome caused by peritoneal lavage with hypertonic solution of NaCl].

We report a case of fatal sodium poisoning due to the unintentional use of 20% hypertonic saline serum during peritoneal lavage after intestinal resection. The patient presented with unconsciousness, metabolic acidosis, and plasma sodium concentration of 193 mE/l. After 3 hours, he developed paroxysmal supraventricular tachycardia, hyperthermia, generalized tonic-clonic convulsions, disseminated intravascular coagulation, and adult respiratory distress syndrome. The patient died 15 hours after the operation. Pathological examination revealed cerebral and lung oedema, pericentral hepatic necrosis, and fibrin thrombi in the lungs, stomach, and kidneys. We review, in addition, other reported cases of sodium poisoning.

Effect of ambient temperature variations on an indigenous microalgae-nitrifying bacteria culture dominated by Chlorella.

Two outdoor photobioreactors were operated to evaluate the effect of variable ambient temperature on an indigenous microalgae-nitrifying bacteria culture dominated by Chlorella. Four experiments were carried out in different seasons, maintaining the temperature-controlled PBR at around 25 °C (by either heating or cooling), while the temperature in the non-temperature-controlled PBR was allowed to vary with the ambient conditions. Temperatures in the range of 15-30 °C had no significant effect on the microalgae cultivation performance. However, when the temperature rose to 30-35 °C microalgae viability was significantly reduced. Sudden temperature rises triggered AOB growth in the indigenous microalgae culture, which worsened microalgae performance, especially when AOB activity made the system ammonium-limited. Microalgae activity could be recovered after a short temperature peak over 30 °C once the temperature dropped, but stopped when the temperature was maintained around 28-30 °C for several days.

Interactions between calcium precipitation and the polyphosphate-accumulating bacteria metabolism.

A sequencing batch reactor that is operated for biological phosphorus removal has been operated under different influent calcium concentrations to study the precipitation process and the possible effects of phosphorus precipitation in the biological phosphorus removal process. Four experiments were carried out under different influent calcium concentrations ranging from 10 to 90 g Ca m(-3). The experimental results and the equilibrium study, which are based on the saturation index calculation, confirm that the process controlling the calcium behaviour is the calcium phosphate precipitation. This precipitation takes place at two stages: initially, precipitation of the amorphous calcium phosphate, and later crystallization of hydroxyapatite. Also the accumulation of phosphorus precipitated was observed when the influent calcium concentration was increased. In all the experiments, the influent wastewater ratio P/COD was kept constant. It has been observed that, at high calcium concentration, the ratio between phosphate release and acetate uptake (P(rel)/Ac(uptake)) decreases. Changes in the polyphosphate-accumulating organism (PAO) population and in the glycogen-accumulating organism (GAO) population during the experimental period were ruled out by means of fluorescence in situ hybridization. These results could suggest that PAO are able to change their metabolic pathways based on external conditions, such as influent calcium concentration. The accumulation of phosphorus precipitated as calcium phosphate at high influent calcium concentration throughout the experimental period confirmed that phosphate precipitation is a process that can affect the PAO metabolism.

Calcium phosphate precipitation in a SBR operated for EBPR: interactions with the biological process.

The aim of this paper is to study the precipitation process in a sequencing batch reactor (SBR) operated for EBPR (enhanced biological phosphorus removal) and the possible effects of this phosphorus precipitation in the biological process. Four experiments were carried out under different influent calcium concentration. The experimental results and the equilibrium study, based on the Saturation Index calculation, confirm that the process controlling the calcium behaviour in a SBR operated for EBPR is the calcium phosphate precipitation. This precipitation takes place at two stages initially precipitation of the ACP and later crystallization of HAP. Also the accumulation of phosphorus precipitated was observed when the influent Ca concentration was increased. In all the experiments the influent wastewater ratio P/COD was kept constant. It has been observed that at high Ca concentration the amount of poly-P granules decrease, decreasing the ratio between phosphate release and acetate uptake (P(rel)/Ac(uptake)). Changes on PAO and GAO populations during the experimental period were ruled out by means of methilene blue stains for poly-P detection. These results confirmed the phosphate precipitation as a process that can affect to the PAO metabolism and the EBPR performance.