Ultrafiltration pretreatment enhances membrane distillation flux, resilience and permeate quality during water recovery from concentrated blackwater (urine/faeces)

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UF is used as a pre-treatment to reduce membrane distillation fouling.

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UF removes particles and colloids from blackwater but low MW fraction increases.

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Whilst UF treated blackwater high in organics, flux and water quality is stable.

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Without UF pre-treatment, severe fouling reduces flux, which reduces quickly.

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With UF pre-treatment, permeate quality consistently meets treatment quality.

In this study, the pretreatment of concentrated blackwater using ultrafiltration (UF) was shown to improve the permeability, selectivity and robustness of membrane distillation (MD) for application to wastewater treatment. Concentrated blackwater comprises urine and faeces, with minimal flushwater added. The faecal contribution increased the soluble organic fraction and introduced coarse and colloidal particles into the urine, which increased resistance to filtration during dead-end UF. Ultrafiltration removed the particulate and colloidal fractions (MW > 500 kDa) from the blackwater, which permitted similar permeability and robustness for MD to that observed with urine (29.9 vs 25.9 kg m⁻² h⁻¹), which comprises a lower colloidal organic concentration. Without UF pretreatment, a higher density organic layer formed on the MD surface (197 vs 70 gCOD m⁻²) which reduced mass transfer, and transformed the contact angle from hydrophobic to hydrophilic (144.9° to 49.8°), leading to pore wetting and a dissipation in product water quality due to breakthrough. In comparison, with UF pretreatment, MD delivered permeate water quality to standards satisfactory for discharge or reuse. This is particularly timely as the ISO standard for non-sewered sanitation has been adopted by several countries at a national level, and to date there are relatively few technologies to achieve the treatment standard. Membrane distillation provides a robust means for concentrated blackwater treatment, and since the energy required for separation is primarily heat, this advanced treatment can be delivered into areas with more fragile power networks.

Managing power dissipation in closed-loop reverse electrodialysis to maximise energy recovery during thermal-to-electric conversion

Whilst the efficiency of reverse electrodialysis (RED) for thermal-to-electrical conversion has been theoretically demonstrated for low-grade waste heat, the specific configuration and salinity required to manage power generation has been less well described. This study demonstrates that operating RED by recycling feed solutions provides the most suitable configuration for energy recovery from a fixed solution volume, providing a minimum unitary cost for energy production. For a fixed membrane area, recycling feeds achieves energy efficiency seven times higher than single pass (conventional operation), and with an improved power density. However, ionic transport, water flux and concentration polarisation introduce complex temporal effects when concentrated brines are recirculated, that are not ordinarily encountered in single pass systems. Regeneration of the concentration gradient at around 80% energy dissipation was deemed most economically pragmatic, due to the increased resistance to mass transport beyond this threshold. However, this leads to significant exergy destruction that could be improved by interventions to better control ionic build up in the dilute feed. Further improvements to energy efficiency were fostered through optimising current density for each brine concentration independently. Whilst energy efficiency was greatest at lower brine concentrations, the work produced from a fixed volume of feed solution was greatest at higher saline concentrations. Since the thermal-to-electrical conversion proposed is governed by volumetric heat utilisation (distillation to reset the concentration gradient), higher brine concentrations are therefore recommended to improve total system efficiency. Importantly, this study provides new evidence for the configuration and boundary conditions required to realise RED as a practical solution for application to sources of low-grade waste heat in industry.

Donation after circulatory death hearts recipients compared to donation after brain death heart recipients have comparable systolic left ventricular function and better myocardial strain at 1 year

Purpose

Cardiac transplantation from donation after circulatory death (DCD) has been implemented at our hospital since February 2015. Despite encouraging results some concerns may be raised about the impact of the warm ischemia and reperfusion injury on the myocardium status at longer follow-up. Therefore, we aimed to analyse systolic performance of the left ventricle at 1 year follow in DCD and donation after brain death (DBD) cardiac recipients, as assessed by echocardiography with myocardial deformation imaging.

Methods

We identified 46 consecutive DCD cardiac recipients who were transplanted from February 2015 to August 2018 and we matched them with 46 DBD cardiac recipients. Six and 7 patients from DCD and DBD group, respectively, died in the first-year post transplant. In the remaining patients we have compared the classical echocardiographic measurements as well as global longitudinal strain (GLS) and global circumferential strain (GCS) at 1-year follow-up.

Results

DCD and DBD patients did not present with differences in terms of classical echocardiographic parameters of left ventricular (LV) structure and systolic function at one-year follow-up. LVEDV was similar in DCD and DBD patients (101±24 vs. 95±32 ml, p=0.4 respectively), as well as LVESV (42±13 vs. 42±16 ml, p=0.9, respectively), LV ejection fraction (58±6 vs. 56±8%, p=0.22) and LV mass (156±39 vs. 163±38 gr, p=0.2, respectively). In contrast, myocardial deformation parameters, such as GLS and GCS, were better in DCD than in DBD (16.1 vs. −14.5%, p<0.01; and −25.2 vs. 22.3%, p<0.05, respectively). The diastolic LV function parameters were similar in DCD and DBD group, as evidenced by E wave velocity, A wave velocity and deceleration time of mitral inflow, however E over E prime was lower in DCD than in DBD recipients (7.7±8.7, p<0.05). Fractional area change of the right ventricle was higher in DCD in comparison with DBD (46±7 vs. 40±7%, p<0.01) while right atrial volume index was lower in DCD than in DBD (25±8 vs. 29±9 ml/m2, p<0.01). Other parameters of RV function (systolic excursion of the tricuspid annulus, TAPSE) were similar in both groups.

Conclusion

DCD and DBD heart recipients present with similar systolic LV function at 1-year follow, as assessed by classical echocardiographic parameters. DCD cardiac recipients have better myocardial deformation parameters as assessed by the speckle tracking, better systolic right ventricular function and lower filling pressures of the left ventricle.

Funding Acknowledgement

Type of funding source: None

A fall in the previous 12 months predicts fracture in the subsequent 5 years in postmenopausal women

PURPOSE

The purpose of this study was to evaluate if a history of falls predicts future postmenopausal fractures and if this prediction variesaccording to frequency, mechanism, and severity of falls and site of fractures.

METHODS

This study used data from OSTPRE prospective cohort. Total study population consisted of 8744 postmenopausal women (mean age 62.2 years) who responded to postal enquiry in 1999 (baseline) and in 2004 (follow-up).

RESULTS

Women were classified by frequency (non/occasional/frequent fallers), mechanism (slip/nonslip), and severity (injurious/ non-injurious) of falls and fractures by site (major osteoporotic/other). A total of 1693 (19.4%) women reported a fall during the preceding 12 months in 1999; 812 a slip fall, 654 a nonslip, 379 an injurious fall, and 1308 a non-injurious fall. A total of 811 women (9.3%) sustained a fracture during the 5-year follow-up period (1999-2004); 431 major osteoporotic fractures and 380 other fractures. Compared with non-fallers, earlier falls predicted subsequent fractures with an OR of 1.41 (95% CI 1.19-1.67, p ≤ 0.001), 1.43 (95% CI 1.14-1.80, p = 0.002) for earlier slip falls, and 1.35 (95% CI 1.04-1.74, p = 0.02) for earlier nonslip falls. Earlier injurious falls predicted future fractures (OR = 1.64, 95% CI 1.21-2.23, p ≤ 0.01), especially other fractures (OR = 1.86, 95% CI 1.24-2.80, p ≤ 0.01), but not major osteoporotic fractures (OR = 1.37, 95% CI 0.89-2.10, p = 0.151). Fracture risk predictions for earlier non-injurious falls was OR = 1.36, 95% CI 1.12-1.64, p = 0.002. These risk patterns remain same after adjustments.

CONCLUSION

History of falls (especially injurious falls) predicts subsequent fractures (mainly other fractures compared with major osteoporotic fractures) inpostmenopausal women. We aimed to investigate if history of falls (frequency, mechanism, and severity) is a predictor of future fractures in postmenopausal women. Our results indicate that history of falls (especially injurious falls) appeared to be an indicator for subsequent fracture overall. Earlier injurious falls were stronger predictors for future other fractures than for typical major osteoporotic fractures.

A simple foot pedal device in a horizontal bore imaging facility replicates weightbearing outcomes for Hallux Valgus patients

BACKGROUND

Weightbearing images are important to the diagnosis of foot pathologies as are the three dimensional views available from CT and MRI. Standard three-dimensional imaging hardware, however, does not have a simple tool to obtain weightbearing images. The current research aimed to design, build and test a simple device to apply load in a horizontal bore imaging facility.

METHODS

With the immediate need in hallux valgus studies, hallux valgus subjects were imaged using the new loading device, which could be easily transported and had no additional electronics.

RESULTS

Testing showed that the usual angular measures of the foot (intermetatarsal and hallux valgus) replicated the results from the standard of care standing plain film results. With application of load, HV angle changed from 29.9° non-weightbearing to 32.2° weightbearing, while IM angle changed from nonweightbearing 15.8° to weightbearing 16.5°.

CONCLUSION

The pedal-like device can provide weightbearing images in a horizontal bore MRI facility.

An assessment of histological margins and recurrence of completely excised cutaneous SCC

There is a paucity of data relating to histological margins of cutaneous squamous cell carcinoma (cSCC) and local recurrence. Retrospective data were collected for 721 patients with cSCC treated at Queen Victoria Hospital, UK, and followed up for five years. The local recurrence rate was 6.1%, the mean time to recurrence was 12.61 months and 93% of recurrences occurred within two years. Sixty-six per cent of recurrences had a deep margin of 2.5 mm or less (p 0.041). The Pearson's correlation coefficient showed a strong correlation with tumour grade (r=0.82, p, 0.05), lymphovascular invasion (r=0.73. p<0.05), medium correlation with deep histological margin(r= -0.55, p<0.05), a weak correlation with male sex (r= 0.31, p<0.05) and the anatomical site of head and neck (r=0.31, p<0.05).The multiple regression analysis model using the 5 variables generated an r value of 0.71 and adjusted r square of 0.7. In conclusion, our findings are consistent with previously mentioned prognostic indicators and also demonstrate that deep histological margin is a significant predictor of local recurrence of cSCC. We recommend larger multi-institutional studies to confirm the above results to subsequently guide the specialist skin multidisciplinary teams' recommendations.

Non-isothermal drying kinetics of human feces

The non-isothermal drying behavior and kinetics of human feces (HF) were investigated by means of thermogravimetric analysis to provide data for designing a drying unit operation. The effect of heating rate and blending with woody biomass were also evaluated on drying pattern and kinetics. At low heating rate (1 K/min), there is effective transport of moisture, but a higher heating rate would be necessary at low moisture levels to reduce drying time. Blending with wood biomass improves drying characteristics of HF. The results presented in this study are relevant for designing non-sewered sanitary systems with in-situ thermal treatment.

A multi-centre randomized controlled trial of open vs closed management of the rectal defect after transanal endoscopic microsurgery

AIM

Transanal endoscopic microsurgery (TEM) is a technically challenging strategy that allows expanded indications for local excision of rectal lesions. Transluminal suturing is difficult, so open management of the resultant defect is appealing. Expert opinion suggests there is more pain when the defect is left open. The aim of this study was to determine if closure of the defect created during full thickness excision of rectal lesions with TEM leads to less postoperative pain compared to leaving the defect open.

METHOD

At the time of surgery, patients undergoing a full thickness TEM were randomized to sutured (TEM-S) or open (TEM-O) management of the rectal defect. At five Canadian academic colorectal surgery centres, experienced TEM surgeons enrolled patients ≥ 18 years treated by full thickness TEM. The primary outcome was postoperative pain measured by the visual analogue scale. Secondary outcomes included postoperative pain medication use and 30-day postoperative complications, including bleeding, infection and hospital readmission.

RESULTS

Between March 2012 and October 2013, 50 patients were enrolled and randomized to sutured (TEM-S, n = 28) or open (TEM-O, n = 22) management of the rectal defect. There was no difference between the two study groups in postoperative pain on postoperative day 1 (2.8 vs 2.6, P = 0.76), day 3 (2.8 vs 2.1, P = 0.23) and day 7 (2.8 vs 1.7, P = 0.10).

CONCLUSION

In this multicentre randomized controlled trial, there was no difference in postoperative pain between sutured or open defect management in patients having a full thickness excision with TEM.

Hybrid membrane distillation reverse electrodialysis configuration for water and energy recovery from human urine: An opportunity for off-grid decentralised sanitation

The integration of membrane distillation with reverse electrodialysis has been investigated as a sustainable sanitation solution to provide clean water and electrical power from urine and waste heat. Reverse electrodialysis was integrated to provide the partial remixing of the concentrate (urine) and diluate (permeate) produced from the membrane distillation of urine. Broadly comparable power densities to those of a model salt solution (sodium chloride) were determined during evaluation of the individual and combined contribution of the various monovalent and multivalent inorganic and organic salt constituents in urine. Power densities were improved through raising feed-side temperature and increasing concentration in the concentrate, without observation of limiting behaviour imposed by non-ideal salt and water transport. A further unique contribution of this application is the limited volume of salt concentrate available, which demanded brine recycling to maximise energy recovery analogous to a battery, operating in a 'state of charge'. During recycle, around 47% of the Gibbs free energy was recoverable with up to 80% of the energy extractable before the concentration difference between the two solutions was halfway towards equilibrium which implies that energy recovery can be optimised with limited effect on permeate quality. This study has provided the first successful demonstration of an integrated MD-RED system for energy recovery from a limited resource, and evidences that the recovered power is sufficient to operate a range of low current fluid pumping technologies that could help deliver off-grid sanitation and clean water recovery at single household scale.

Non-isothermal thermogravimetric kinetic analysis of the thermochemical conversion of human faeces

The "Reinvent the Toilet Challenge" set by the Bill & Melinda Gates Foundation aims to bring access to adequate sanitary systems to billions of people. In response to this challenge, on-site sanitation systems are proposed and being developed globally. These systems require in-situ thermal treatment, processes that are not well understood for human faeces (HF). Thermogravimetric analysis has been used to investigate the pyrolysis, gasification and combustion of HF. The results are compared to the thermal behaviour of simulant faeces (SF) and woody biomass (WB), along with the blends of HF and WB. Kinetic analysis was conducted using non-isothermal kinetics model-free methods, and the thermogravimetric data obtained for the combustion of HF, SS and WB. The results show that the devolatilisation of HF requires higher temperatures and rates are slower those of WB. Minimum temperatures of 475 K are required for fuel ignition. HF and SF showed similar thermal behaviour under pyrolysis, but not under combustion conditions. The activation energy for HF is 157.4 kJ/mol, relatively higher than SS and WB. Reaction order for HF is lower (n = 0.4) to WB (n = 0.6). In-situ treatment of HF in on-site sanitary systems can be designed for slow progressive burn.

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Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.