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Objectives: The objective of this study is to assess the effect of reminder text messages 6 months after the initial treatment on retest and chlamydia reinfection rates in young heterosexuals compared with a historical control group and to assess factors associated with both outcomes.Methods: Heterosexual people (aged 16-23 years), testing positive for urogenital chlamydia, were offered a retest after 6 months. Participants received a text message reminder at 6 months after the initial chlamydia diagnosis. Rates of retest uptake and the result of the retest were analysed using Cox regression. Prevalence ratios (PRs) were calculated to identify factors associated with these outcomes. Furthermore, the retest rate was compared with the retest rate of a historical control group.Results: 30.6% (253/838) of the study group returned within 5-8 months compared with 9.2% (140/1530) in the historical control group. Women and persons who were not notified for a sexually transmitted infection (STI) at inclusion were more likely to return for a retest. 20.4% (56/275) of participants had a chlamydia reinfection upon retesting. Reinfection was higher in participants reporting STI-related symptoms (PR 3.2, 95% CI 1.8 to 5.6) and in participants who were notified for an STI at retest (PR 5.3, 95% CI 2.4 to 11.5).Conclusions: A text message reminder appeared to have a clear, positive impact on the resulting retest rate. These results also indicate that retesting is necessary to identify chlamydia reinfections. [ABSTRACT FROM AUTHOR]

Drug use during sex ('chemsex') has been associated with sexually transmitted infections (STIs) and mental health harms. Little quantitative evidence exists on the health care needs of MSM practicing chemsex from a patient perspective. This study assessed self-perceived benefits and harms and the needs for professional counselling among MSM practicing chemsex. In 2018, 785 MSM were recruited at nine Dutch STI clinics and 511 (65%) completed the online questionnaire. Chemsex was defined as using cocaine, crystal meth, designer drugs, GHB/GBL, ketamine, speed and/or XTC/MDMA during sex <6 months. Chemsex was reported by 41% (209/511), of whom 23% (48/209) reported a need for professional counselling. The most reported topic to discuss was increasing self-control (52%, 25/48). Most MSM preferred to be counselled by sexual health experts (56%, 27/48). The need for professional counselling was higher among MSM who engaged in chemsex ≥2 times per month (30% vs. 17%, p = 0.03), did not have sex without drugs (sober sex) in the past three months (41% vs. 20%, p = 0.04), experienced disadvantages of chemsex (28% vs. 15%, p = 0.03), had a negative change in their lives due to chemsex (53% vs. 21%, p = 0.002), and/or had an intention to change chemsex behaviours (45% vs. 18%, p < 0.001). Our study shows that almost one in four MSM practicing chemsex expressed a need for professional counselling on chemsex-related issues. STI healthcare providers should assess the need for professional counselling in MSM practicing chemsex, especially in MSM with above mentioned characteristics, such as frequent users., (© 2020 The Author(s).)

Chemical energy can be recovered from municipal wastewater as biogas through anaerobic treatment. Effluent from direct anaerobic wastewater treatment at low temperatures, however, still contains ammonium and considerable amounts of dissolved methane. After nitritation, methane can be used as electron donor for denitrification by the anaerobic bacterium 'Candidatus Methylomirabilis oxyfera'. It was shown that in the presence of 0.7% O 2, denitrifying methanotrophic activity slightly increased and returned to its original level after oxygen had been removed. At 1.1% O 2 , methane consumption rate increased 118%, nitrite consumption rate increased 58%. After removal of oxygen, methane consumption rate fully recovered, and nitrite consumption rate returned to 88%. Therefore, traces of oxygen that bacteria are likely to be exposed to in wastewater treatment are not expected to negatively affect the denitrifying methanotrophic process. 2.0% O 2 inhibited denitrifying activity. Nitrite consumption rate decreased 60% and did not recover after removal of oxygen. No clear effect on methane consumption was observed. Further studies should evaluate if intermittent addition of oxygen results in increased growth rates of the slow-growing 'Candidatus Methylomirabilis oxyfera'.

Anammox in the water line of a waste water treatment plant (WWTP) saves energy for aeration and allows for recovering biogas from organic material. Main challenges for applying the anammox process in the water line are related to the low temperature of <20°C, causing a significant drop in the specific anammox activity. The aim of this research was to enrich a cold-adapted anammox species, with a high specific activity. This was achieved in a 4.2L reactor operated at 10°C, fed with 61 mg (NH4+NO2)-N/L and inoculated with activated sludge from two selected municipal WWTPs. Candidatus Brocadia fulgida was the dominant species in the enriched biomass, with a specific activity was 30-44 mg N/(g VS d). This is two times higher than previously reported at 10°C, which is beneficial for full scale application. Biomass yield was 0.046 g biomass/g N converted, similar to that at higher temperatures., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Simultaneous nitrogen and methane removal by the slow growing denitrifying methanotrophic bacterium 'Candidatus Methylomirabilis oxyfera' offers opportunities for a new approach to wastewater treatment. However, volumetric nitrite consumption rates should be increased by an order of magnitude before application in wastewater treatment becomes possible. A maximum volumetric nitrite consumption rate of 36 mg NO2(-)-N/L d was achieved in a membrane bioreactor inoculated with wastewater sludge and operated at 20°C. This rate is similar to maximum rates reported in literature, though it was thought that by strict biomass retention using membranes, higher rates would be achieved. In experiments lasting several years, growth was not stable: every experiment showed a decrease in activity after 1-2 years. The cause remains unknown. Rates increased after addition of copper and operating a membrane bioreactor at shorter hydraulic retention times. Further research should focus on long-term effects of copper addition and operation at hydraulic retention times in the order of hours using membrane bioreactors., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The activity of denitrifying methanotrophic bacteria at 11-30 °C was assessed in short-term experiments. The aim was to determine the feasibility of applying denitrifying methanotrophic bacteria in low-temperature anaerobic wastewater treatment. This study showed that biomass enriched at 21 °C had an optimum temperature of 20-25 °C and that activity dropped as temperature was increased to 30 °C. Biomass enriched at 30 °C had an optimum temperature of 25-30 °C. These results indicated that biomass from low-temperature inocula adjusted to the enrichment temperature and that low-temperature enrichment is suitable for applications in low-temperature wastewater treatment. Biomass growth at ≤20 °C still needs to be studied.

The aim of this work was to demonstrate that co-digestion improves soluble sewage COD removal efficiency in treatment of low temperature municipal sewage by a UASB-digester system. A pilot scale UASB-digester system was applied to treat real municipal sewage, and glucose was chosen as a model co-substrate. Co-substrate was added in the sludge digester to produce additional methanogenic biomass, which was continuously recycled to inoculate the UASB reactor. Soluble sewage COD removal efficiency increased from 6 to 23%, which was similar to its biological methane potential (BMP). Specific methanogenic activity of the UASB and of the digester sludge at 15°C tripled to a value respectively of 43 and 39 mg CH4-COD/(g VSS d). Methane production in the UASB reactor increased by more than 90% due to its doubled methanogenic capacity. Therefore, co-digestion is a suitable approach to support a UASB-digester for pretreatment of low temperature municipal sewage., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Despite many advantages of anaerobic sewage treatment over conventional activated sludge treatment, it has not yet been applied in temperate zones. This is especially because effluent from low-temperature anaerobic treatment contains nitrogen and dissolved methane. The presence of nitrogen and methane offers the opportunity to develop a reactor in which methane is used as electron donor for denitrification. Such a reactor could be used in a new concept for low-temperature anaerobic sewage treatment, consisting of a UASB-digester system, a reactor for denitrification coupled to anaerobic methane oxidation, and a nitritation reactor. In the present study denitrifying methanotrophic bacteria similar to 'Candidatus Methylomirabilis oxyfera' were enriched. Maximum volumetric nitrite consumption rates were 33.5 mg NO(2)(-)-N/Ld (using synthetic medium) and 37.8 mg NO(2)(-)-N/Ld (using medium containing effluent from a sewage treatment plant), which are similar to the maximum rate reported so far. Though the goal was to increase the rates, in both reactors, after reaching these maximum rates, volumetric nitrite consumption rates decreased in time. Results indicate biomass washout may have significantly decelerated enrichment. Therefore, to obtain higher volumetric consumption rates, further research should focus on systems with complete biomass retention., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Direct anaerobic treatment of municipal waste waters allows for energy recovery in the form of biogas. A further decrease in the energy requirement for waste water treatment can be achieved by removing the ammonium in the anaerobic effluent with an autotrophic process, such as anammox. Until now, anammox has mainly been used for treating warm (>30 °C) and concentrated (>500 mg N/L) waste streams. Application in the water line of municipal waste water treatment poses the challenges of a lower nitrogen concentration (<100 mg N/L) and a lower temperature (≤ 20 °C). Good biomass retention and a short HRT are required to achieve a sufficiently high nitrogen loading rate. For this purpose a 4.5 L gaslift reactor was inoculated with a small amount of anammox granules and operated for 253 days at 20 °C. The synthetic influent contained (69 ± 5) mg (NH(4)(+) + NO(2)(-))/L and 20 vol.% of anaerobically stabilised effluent. Results showed a clear increase in nitrogen loading rate (NLR) up to 0.31 g (NH(4) + NO(2))-N/(L × d) at a hydraulic retention time (HRT) of 5.3 h. A low effluent concentration of 0.03-0.17 mg (NH(4)(+)+NO(2)(-))-N/L could be achieved. Anammox biomass was retained as granules and as a biofilm on the reactor walls, which contributed 54 and 46%, respectively, towards total activity. The biomass was further characterised by an estimated net growth rate of 0.040 d(-1) and an apparent activation energy of 72 kJ/mol. The results presented in this paper showed that anammox bacteria can be applied for autotrophic nitrogen removal from the water line at a municipal waste water treatment plant. Combining direct anaerobic treatment with autotrophic nitrogen removal opens opportunities for energy-efficient treatment of municipal waste waters., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The anaerobic treatment of low strength domestic sewage at low temperature is an attractive and important topic at present. The upflow anaerobic sludge bed (UASB)-digester system is one of the anaerobic systems to challenge low temperature and concentrations. The effect of sludge recirculation rate on a UASB-digester system treating domestic sewage at 15 °C was studied in this research. A sludge recirculation rate of 0.9, 2.6 and 12.5% of the influent flow rate was investigated. The results showed that the total chemical oxygen demand (COD) removal efficiency rose with increasing sludge recirculation rate. A sludge recirculation rate of 0.9% of the influent flow rate led to organic solids accumulation in the UASB reactor. After the sludge recirculation rate increased from 0.9 to 2.6%, the stability of the UASB sludge was substantially improved from 0.37 to 0.15 g CH₄-COD/g COD, and the bio-gas production in the digester went up from 2.9 to 7.4 L/d. The stability of the UASB sludge and bio-gas production in the digester were not significantly further improved by increasing sludge recirculation rate to 12.5% of the influent flow rate, but the biogas production in the UASB increased from 0.37 to 1.2 L/d. It is recommended to apply a maximum sludge recirculation rate of 2-2.5% of the influent flow rate in a UASB-digester system, as this still allows energy self-sufficiency of the system.

Recently discovered microorganisms affiliated to the bacterial phylum NC10, named "Candidatus Methylomirabilis oxyfera", perform nitrite-dependent anaerobic methane oxidation. These microorganisms could be important players in a novel way of anaerobic wastewater treatment where ammonium and residual dissolved methane might be removed at the expense of nitrate or nitrite. To find suitable inocula for reactor startup, ten selected wastewater treatment plants (WWTPs) located in The Netherlands were screened for the endogenous presence of M. oxyfera using molecular diagnostic methods. We could identify NC10 bacteria with 98% similarity to M. oxyfera in nine out of ten WWTPs tested. Sludge from one selected WWTP was used to start a new enrichment culture of NC10 bacteria. This enrichment was monitored using specific pmoA primers and M. oxyfera cells were visualized with fluorescence oligonucleotide probes. After 112 days, the enrichment consumed up to 0.4 mM NO(2)(-) per day. The results of this study show that appropriate sources of biomass, enrichment strategies, and diagnostic tools existed to start and monitor pilot scale tests for the implementation of nitrite-dependent methane oxidation in wastewater treatment at ambient temperature., (© The Author(s) 2011. This article is published with open access at Springerlink.com)

Biological acetate reduction with hydrogen is a potential method to convert wet biomass waste into ethanol. Since the ethanol concentration and reaction rates are low, this research studies the feasibility of using an electrode, in stead of hydrogen, as an electron donor for biological acetate reduction in conjunction of an electron mediator. Initially, the effect of three selected mediators on metabolic flows during acetate reduction with hydrogen was explored; subsequently, the best performing mediator was used in a bioelectrochemical system to stimulate acetate reduction at the cathode with mixed cultures at an applied cathode potential of -550 mV. In the batch test, methyl viologen (MV) was found to accelerate ethanol production 6-fold and increased ethanol concentration 2-fold to 13.5 +/- 0.7 mM compared to the control. Additionally, MV inhibited n-butyrate and methane formation, resulting in high ethanol production efficiency (74.6 +/- 6%). In the bioelectrochemical system, MV addition to an inoculated cathode led directly to ethanol production (1.82 mM). Hydrogen was coproduced at the cathode (0.0035 Nm(3) hydrogen m(-2) d(-1)), so it remained unclear whether acetate was reduced to ethanol by electrons supplied by the mediator or by hydrogen. As MV reacted irreversibly at the cathode, ethanol production stopped after 5 days.