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The effect of salinity on aerobic granular sludge treating fish-canning wastewater was evaluated through a one-dimensional biofilm model. Salt inhibition of heterotrophic and nitrifying bacteria was described by a non-competitive inhibition term, for which the value of the half-saturation coefficient was estimated based on data from literature. The model was calibrated and validated with experimental lab-scale data regarding COD and nitrogen removal from industrial wastewater. Two dynamic operating periods with salinities of 13 and 5 g NaCl L-1 were used for calibration and validation, respectively. The prevailing feast-famine regime necessitated simultaneous growth and storage processes to accurately describe COD removal. The presence of salt caused nitrite accumulation, as well as unusually low estimated maximum growth rates of nitrifying bacteria. The addition of a salinity inhibition term to the model could accurately describe the COD and nitrogen species experimentally measured along the cycles with different salinities.

Branko Kerkez, Kris Villez and Eveline I. P. Volcke introduce the Environmental Science: Water Research & Technology themed issue on data-intensive water systems management and operation.

Partial nitration-anammox is a resource-efficient technology for nitrogen removal from wastewater. However, the advantages of this nitrogen removal technology are challenged by the emission of N(2)O, a potent greenhouse gas. In this study, a granular sludge one-stage partial nitritation-anammox reactor comprising granules and flocs was run for 337 days in the presence of influent organics to investigate its effect on N removal and N(2)O emissions. Besides, the effect of aeration control strategies and flocs removal were investigated as well. The interpretation of the experimental results was complemented with modelling and simulation. The presence of influent organics (1 g COD g(-1) N) helped to suppress NOB and significantly reduced the overall N(2)O emissions while having no significant effect on anammox activity. Besides, long-term monitoring of the reactor indicated that constant airflow rate control resulted in more stable effluent quality and less N(2)O emissions than DO control. Still, floc removal reduced N(2)O emissions at DO control but increased N(2)O emissions at constant airflow rate. Furthermore, anammox bacteria could significantly reduce N(2)O production during heterotrophic denitrification, likely via competition for NO with heterotrophs. Overall, this study demonstrated that the presence of influent organics together with proper aeration control strategies and floc management could significantly reduce the N(2)O emissions without compromising nitrogen removal efficiency during one-stage partial nitritation-anammox processes.

This study deals with the effect of aeration control strategies on the nitrogen removal efficiency and nitrous oxide (N(2)O) emissions in a partial nitritation-anammox reactor with granular sludge. More specifically, dissolved oxygen (DO) control, constant airflow and effluent ammonium (NH(4)(+)) control strategies were compared through a simulation study. Particular attention was paid to the effect of flocs, which are deliberately or unavoidable present besides granules in this type of reactor. When applying DO control, DO setpoints had to be adjusted to the amount of flocs present in the reactor to maintain high nitrogen removal and reduce N(2)O emissions, which is difficult to realize in practice because of variable floc fractions. Constant airflow rate control could maintain a good nitrogen removal efficiency independent of the floc fraction in the reactor, but failed in N(2)O mitigation. Controlling the effluent ammonium concentration results in both high nitrogen removal and relatively low N(2)O emissions, also in the presence of flocs. Fluctuations in floc fractions caused significant upsets in nitrogen removal and N(2)O emissions under DO control but had less effect at constant airflow and effluent ammonium control. Still, rapid and sharp drops in flocs led to a peak in N(2)O emissions at constant airflow and effluent ammonium control. Overall, effluent ammonium control reached the highest average nitrogen removal and lowest N(2)O emissions and consumed the lowest aeration energy under fluctuating floc concentrations.

Multivariate statistical analysis was applied to investigate the dependencies and underlying patterns between N

Aquasim is public-domain and user-friendly software that is widely used for biofilm modeling. The program uses built-in process unit blocks, such as biofilm and mixed compartments. In the literature, often several of these compartments are linked with artificial advective flows to represent a single physical well-mixed system, such as a granular sludge reactor. This work shows that caution should be exercised with this popular approach because numerical errors occur when too high artificial advective flows are used. These errors could stay unnoticed if mass-balances of the simulation results are not checked. A solution to this problem is proposed in this work. A new method based on diffusive links between compartments instead of advective links leads to more reliable and faster simulations and is much easier to implement. Biotechnol. Bioeng. 2017;114: 2131-2136. © 2017 Wiley Periodicals, Inc.

For engineers, it is interesting to gain insight in the effect of control strategies on microbial communities, on their turn influencing the process behavior and its stability. This contribution assesses the influence of process dynamics on the microbial community in a biofilm reactor for nitrogen removal, which was controlled according to several strategies aiming at nitrite accumulation. The process dataset, combining conventional chemical and physical data with molecular information, was analyzed through a correlation analysis and in a simulation study. During nitrate formation, an increased nitrogen loading rate (NLR) resulted in a drop of the bulk liquid oxygen concentration without resulting in nitrite accumulation. A biofilm model was able to reproduce the bulk liquid nitrogen concentrations in two periods before and after this increased NLR. As the microbial parameters calibrated for the ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in both periods were different, it was concluded that the increased NLR governed an AOB and NOB population shift. Based on the molecular data, it was assumed that each period was typified by one dominant AOB and probably several subdominant NOB populations. The control strategies for nitrite accumulation influenced the bulk liquid composition by controlling the competition between AOB and NOB. Biotechnol. Bioeng. 2016;113: 1962-1974. © 2016 Wiley Periodicals, Inc.

In this paper, the authors report the results of a genetic-diagnostic survey of 262 instutionalized moderately mentally retarded patients and compare these data with their previous studies of the severely mentally retarded. Special attention is given towards the nosology of X-linked mental retardation and familial mental retardation in general.

In this report we describe two fra(X) adults and two prepubertal fra(X) brothers with a combination of distinct phenotypic findings: extreme obesity, short stature, stubby hands and feet and diffuse hyper-pigmentation. These clinical abnormalities may be an additional indication of a specific hypothalamic disturbance in the fra(X) syndrome.

A large variety of microbial parameter values for nitrifying microorganisms has been reported in literature and was revised in this study. Part of the variety was attributed to the variety of analysis methods applied; it also reflects the large biodiversity in nitrifying systems. This diversity is mostly neglected in conventional nitrifying biofilm models. In this contribution, a one-dimensional, multispecies nitrifying biofilm model was set up, taking into account the large variety of the maximum growth rate, the substrate affinity and the yield of nitrifiers reported in literature. Microbial diversity was implemented in the model by considering 60 species of ammonia-oxidizing bacteria (AOB) and 60 species of nitrite-oxidizing bacteria (NOB). A steady-state analysis showed that operational conditions such as the nitrogen loading rate and the bulk liquid oxygen concentration influence both the macroscopic output as well as the microbial composition of the biofilm through the prevailing concentration of substrates throughout the biofilm. Considering two limiting resources (nitrogen and oxygen), the coexistence of two species of the same functional guild (AOB or NOB) was possible at steady state. Their spatial distribution in the biofilm could be explained using the r- and K-selection theory.

N₂O emission from wastewater treatment plants is high of concern due to the strong environmental impact of this greenhouse gas. Good understanding of the factors affecting the emission and formation of this gas is crucial to minimize its impact. This study addressed the investigation of the N₂O emission dynamics in a full-scale one-stage granular sludge reactor performing partial nitritation-anammox (PNA) operated at a N-loading of 1.75 kg NH₄⁺-N m⁻³ d⁻¹. A monitoring campaign was conducted, gathering on-line data of the N₂O concentration in the off-gas of the reactor as well as of the ammonium and nitrite concentrations in the liquid phase. The N₂O formation rate and the liquid N₂O concentration profile were calculated from the gas phase measurements. The mean (gaseous) N₂O-N emission obtained was 2.0% of the total incoming nitrogen during normal reactor operation. During normal operation of the reactor under variable aeration rate, intense aeration resulted in higher N₂O emission and formation than during low aeration periods (mean N₂O formation rate of 0.050 kg N m⁻³ d⁻¹ for high aeration and 0.029 kg N m⁻³ d⁻¹ for low aeration). Accumulation of N₂O in the liquid phase was detected during low aeration periods and was accompanied by a relatively lower ammonium conversion rate, while N₂O stripping was observed once the aeration was increased. During a dedicated experiment, gas recirculation without fresh air addition into the reactor led to the consumption of N₂O, while accumulation of N₂O was not detected. The transition from a prolonged period without fresh air addition and with little recirculation to enhanced aeration with fresh air addition resulted in the highest N₂O formation (0.064 kg N m⁻³ d⁻¹). The results indicate that adequate aeration control may be used to minimize N₂O emissions from PNA reactors.

This case report describes chronic exertional compartment syndrome in the forearm of a professional rower. We consider this to be a rare anatomical location for this type of syndrome. Morever, not much is known about its clinical presentation and the subsequent optimal medical management thereof.

The combined SHARON-Anammox process for treating wastewater streams with high ammonia concentration is discussed. Partial nitritation in the SHARON reactor should be performed to such an extent that an Anammox-optimal nitrite:ammonium ratio is generated. The SHARON process is typically applied to sludge digestion rejection water in order to relieve the ammonium load recycled to the main plant. A simulation study for realistic influent conditions on a SHARON reactor with a fixed volume and operated with constant air flow rate reveals that the actual nitrite:ammonium ratio might deviate significantly from the ideal ratio and might endanger operation of the subsequent Anammox reactor. It is further examined how the nitrite:ammonium ratio might be optimized. A cascade pH control strategy and a cascade O2 control strategy are tested. Simulation results are presented and the performance of the different strategies is assessed and quantified in an economic way by means of an operating cost index. Best results are obtained by means of cascade feedback control of the SHARON effluent nitrite:ammonium ratio through setting an O2-set-point that is tracked by adjusting the air flow rate.

Partial nitrification techniques, such as the continuously aerated SHARON process, have been denoted for quite a while as very promising for improved sustainability of wastewater treatment. Combination of such a SHARON process with the Anammox process, where ammonium is oxidised with nitrite to nitrogen gas under anoxic conditions, leads to cost-efficient and sustainable nitrogen removal from concentrated streams. In this study practical experiences during start-up and operation of a lab-scale SHARON reactor are discussed. Special attention is given to the start-up in view of possible toxic effects of high ammonium and nitrite concentrations (up to 4000 mgN/l) on the nitrifier population and because the reactor was inoculated with sludge from a SBR reactor operated under completely different conditions. Because of these considerations, the reactor was first operated as a SBR to prevent biomass wash out and to allow the selection of a strong nitrifying population. A month after the inoculation the reactor was switched to normal chemostat operation. As a result the nitrite oxidisers were washed out and only the ammonium oxidisers persisted in the reactor. In this contribution also some practical considerations, such as mixing, evaporation and wall growth, concerning the operation of a continuously aerated SHARON reactor are discussed. These considerations are not trivial, since the reactor will be used for kinetic characterisation and modelling studies. Finally the performance of the SHARON reactor under different conditions is discussed in view of its coupling with an Anammox unit. Full nitrification was proven to be feasible for nitrogen loads up to 1.5 g/l d, indicating the possibility of the SHARON process to treat highly loaded nitrogen streams.

Two families with nonspecific X-linked mental retardation (MRX) are presented. In the first family, MRX51, three male patients showed mild to borderline mental retardation. Multipoint linkage analysis yielded a maximal LOD score of 2.10 between markers DXS8012 and DXS1003, localizing the MRX51 gene at Xp11.3-p11.23. In the second family, XLMR7, three men showed moderate mental retardation (MR), and one possible female carrier had mild MR. Multipoint linkage analysis yielded an LOD score of 1.80 between markers DXS8063 and DXS1047, situating the disease gene at Xq23-q26.1. When the analysis was performed considering the affected female to be an expressing heterozygote carrier of the disease mutation, a maximal LOD score of 2.10 was found in the same region.

During a systematic survey for genetic causes of mental retardation in schools for adolescents with learning problems we had the occasion to examine a 16-year-old moderately mentally retarded boy with facial dysmorphism, short stature, relative microcephaly, complete cutaneous syndactyly of fingers III/IV and of toes II/III. Partial clinical manifestations (low to subnormal intelligence and syndactyly) were present in his mother and sister. We discuss the nosology and differential diagnosis of the craniodigital syndromes.

Two cases are presented with a phenotype mostly resembling the condition named Marden-Walker syndrome. Main features of this condition are blepharophimosis, micrognatia, congenital joint contractures, mental retardation, growth retardation and decreased muscular mass. Follow-up data of patients with this condition are scarce and most patients reported so far were infants or young children. We report two patients meeting many of the criteria proposed for diagnosing this particular phenotype. One case was diagnosed in adolescence and the other as an adult. Initially described as a syndrome, this condition is more likely to be a phenotypic expression of various heterogeneous diseases.

In this report we present follow-up data on a family in which several members were found to have short stature, craniofacial anomalies and dento-skeletal abnormalities (KBG-syndrome). As adults, the three affected brothers of the original report are moderately to severely mentally retarded. Their phenotype with a distinct craniofacial appearance did not change much from that seen during childhood and adolescence. Adult height is far below the third centile, with arm spans exceeding stature by at least 9 cm.

During a systematic clinical genetic survey of the institutionalized moderately to severely mentally retarded we had the occasion to examine two nonrelated adult patients who presented a similar MCA/MR syndrome: 1) macrocephaly (OFC60 cm) with high and broad forehead and contrasting relative midfacial hypoplasia; 2) short stature with small and broad hands and feet; 3) neurological symptoms of a variable degree of spastic paraplegia and severe CNS malformations on CT-scan i.e. internal hydrocephalus and Dandy-Walker variant malformation.

A large, three generation-family with firm evidence of autosomal dominant transmission of the cardio-faciocutaneous (CFC) syndrome is reported. This observation questions once more the validity of separating the CFC syndrome from the Noonan syndrome as two distinct entities.