Starting position during colonoscopy: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Traditional teaching has been to place patients in the left lateral decubitus starting position for colonoscopies. Recent randomized controlled trials (RCTs) have compared left lateral decubitus starting position to other approaches. The aim of this systematic review and meta-analysis was to compare different starting positions for colonoscopies and their effect on cecal intubation. METHODS: MEDLINE, Embase, and CENTRAL were searched from inception to July 2023. Articles were eligible for inclusion if they were RCTs comparing at least two different starting positions for adults undergoing colonoscopy. The main outcome was cecal intubation time. Meta-analysis used an inverse variance random effects model. Risk of bias was assessed with the Cochrane Tool for RCTs 2.0. RESULTS: After screening 1523 citations, 14 RCTs were included. Four studies compared left lateral decubitus to right lateral decubitus, four studies compared left lateral decubitus to left lateral tilt-down, three studies compared left lateral decubitus to prone, and three studies compared left lateral decubitus to supine. There were no statistically significant differences in cecal intubation time in seconds across all comparisons: left lateral decubitus vs. right lateral decubitus (MD 14.9, 95% CI - 111.8 to 141.6, p = 0.82, I2 = 85%); left lateral decubitus vs. left lateral tilt-down (MD - 31.3, 95% CI - 70.8 to 8.3, p = 0.12, I2 = 82%); left lateral decubitus vs. prone (MD 17.2, 95% CI - 174.9 to 209.4, p = 0.86, I2 = 94%); left lateral decubitus vs. supine (MD - 149.9, 95% CI - 443.6 to 143.9, p = 0.32, I2 = 89%). CONCLUSION: The starting position for colonoscopies likely does not influence cecal intubation time. This study was limited by heterogeneity.

The modified frailty index predicts postoperative morbidity in elective hernia repair patients: analysis of the national inpatient sample 2015-2019.

PURPOSE: Frailty has shown promise in predicting postoperative morbidity and mortality following hernia surgery. This study aims to evaluate the predictive capacity of the 11-item modified frailty index (mFI) in estimating postoperative outcomes following elective hernia surgery using the National Inpatient Sample (NIS) database. METHODS: A retrospective analysis of the NIS from 2015 to 2019 was performed including adult patients who underwent elective hernia repair. The mFI was used to stratify patients as either frail (mFI ≥ 0.27) or robust (mFI < 0.27). The primary outcomes were in-hospital postoperative morbidity and mortality. The secondary outcomes were system-specific morbidity, length of stay (LOS), total in-hospital healthcare cost, and discharge disposition. Univariable and multivariable regressions were utilized. RESULTS: In total, 14,125 robust patients and 1704 frail patients were included. Frailty was associated with an increased age (mean age 66.4 years vs. 52.6 years, p < 0.001) and prevalence of ventral hernias (51.9% vs. 44.4%, p < 0.001). Adjusted analyses demonstrated that frail patients had increased in-hospital mortality (adjusted odds ratio (aOR) 3.89, 95% CI 1.50, 10.11, p = 0.005), postoperative overall morbidity (aOR 1.98, 95% CI 1.72, 2.29, p < 0.001), postoperative LOS (adjusted mean difference (aMD) 0.78 days, 95% CI 0.51, 1.06, p < 0.001), total in-hospital healthcare costs (aMD $7562 95% CI 3292, 11,832, p = 0.001), and were less likely to be discharged home (aOR 0.61, 95% CI 0.53, 0.69, p < 0.001). CONCLUSION: The mFI may be a reliable predictor of postoperative morbidity and mortality in elective hernia surgery. Utilizing this tool can aid in patient education and identifying high-risk patients who may benefit from tailored prehabilitation.

Cutting seton for the treatment of cryptoglandular fistula-in-ano: a systematic review and meta-analysis.

BACKGROUND: The use of cutting seton (CS) for the management of cryptoglandular fistula-in-ano has remained controversial because of reports of fecal incontinence, postoperative pain, and extended healing time. The aim of this review was to provide the first synthesis of studies investigating the use of CS for the treatment of cryptoglandular fistula-in-ano. METHODS: MEDLINE, Embase, and CENTRAL were searched up to October 2022. Randomized controlled trials and observational studies comparing CS with alternative interventions were included, along with single-arm studies evaluating CS alone. The primary outcome was fistula-in-ano recurrence, and secondary outcomes included incontinence, healing time, proportion with complete healing, and postoperative pain. Inverse variance random-effects meta-analyses were used to pool effect estimates. RESULTS: After screening 661 citations, 29 studies were included. Overall, 1513 patients undergoing CS (18.8% female, mean age: 43.1 years) were included. Patients with CS had a 6% (95% CI: 3-12%) risk of recurrence and a 16% (95% CI: 5-38%) risk of incontinence at 6 months. CS patients had an average healing time of 14.6 weeks (95% CI: 10-19 weeks) with 73% (95% CI: 48-89%) of patients achieving complete healing at 6 months postoperatively. There was no difference in recurrence between CS and fistulotomy, advancement flap, two-stage seton fistulotomy, or draining seton. CONCLUSIONS: Overall, this analysis shows that CS has comparable recurrence and incontinence rates to other modalities. However, this may be at the expense of more postoperative pain and extended healing time. Further comparative studies between CS and other modalities are warranted.

Extended thromboprophylaxis following colorectal surgery in patients with inflammatory bowel disease: a comprehensive systematic clinical review.

AIM: Patients with inflammatory bowel disease (IBD) are at increased risk of postoperative venous thromboembolism (VTE) following major abdominal surgery. The pathogenesis is multifactorial and not fully understood. A combination of pathophysiology, patient and surgical risk factors increase the risk of postoperative VTE in these patients. Despite being at increased risk, IBD patients are not regularly prescribed extended pharmacological thromboprophylaxis following colorectal surgery. Currently, there is a paucity of evidence-based guidelines. Thus, the aim of this review is to evaluate the role of extended pharmacological thromboprophylaxis in IBD patients undergoing colorectal surgery. METHOD: A search of Ovid Medline, EMBASE and PubMed databases was performed. A qualitative analysis was performed using 10 clinical questions developed by colorectal surgeons and a thrombosis haematologist. The Newcastle-Ottawa Scale was utilized to assess the quality of evidence. RESULTS: A total of 1229 studies were identified, 38 of which met the final inclusion criteria (37 retrospective, one case-control). Rates of postoperative VTE ranged between 0.6% and 8.9%. Patient-specific risk factors for postoperative VTE included ulcerative colitis, increased age and obesity. Surgery-specific risk factors for postoperative VTE included open surgery, emergent surgery and ileostomy creation. Patients with IBD were more frequently at increased risk in the included studies for postoperative VTE than patients with colorectal cancer. The risk of bias assessment demonstrated low risk of bias in patient selection and comparability, with variable risk of bias in reported outcomes. CONCLUSION: There is a lack of evidence regarding the use of extended pharmacological thromboprophylaxis in patients with IBD following colorectal surgery. As these patients are at heightened risk of postoperative VTE, future study and consideration of the use of extended pharmacological thromboprophylaxis is warranted.

Fate of sterols, polycyclic aromatic hydrocarbons, pharmaceuticals, ammonia and solids in single-stage anaerobic and sequential anaerobic/aerobic/anoxic sludge digestion.

Emerging contaminants (ECs), such as pharmaceuticals, sterols and polycyclic aromatic hydrocarbons (PAHs) are frequently detected in the environment. ECs are refractory, toxic, tend to bioaccumulate and have a potential to disrupt the endocrine system of living organisms. These compounds are only partially eliminated in wastewater treatment plants (WWTPs). Due to their hydrophobic nature, they tend to accumulate in sludge. However, the fate of the majority of ECs in sludge treatment processes is not fully understood. In this study, the effect of a sequential anaerobic/aerobic/anoxic (AN/AERO/ANOX) digestion and a conventional single-stage AN digestion (as control) was investigated on mixed primary and secondary sludge. Digesters were operated at an overall solid retention time (SRT) of 18 days. The steady-state results have shown that sequential AN/AERO/ANOX digestion configurations improved the removal of three classes of ECs (e.g., sterols, PAHs and pharmaceuticals) by either reducing their accumulation or enhancing their removal. Moreover, sequential AN/AERO/ANOX digestion also achieved 45% less ammonia generation, 20% faster digestate dewaterability and 4% enhanced volatile solids removal compared to single-stage AN digestion.

Comparison of Different Electricity-Based Thermal Pretreatment Methods for Enhanced Bioenergy Production from Municipal Sludge.

This paper presents results for a comprehensive study that compares the performance of three electricity-based thermal pretreatment methods for improving the effectiveness of anaerobic digestion (AD) to process municipal wastewater sludge. The study compares thermal pretreatment using conventional heating (CH), microwave (MW), and radio frequency (RF) heating techniques. The effectiveness of the pretreatment methods was assessed in terms of chemical oxygen demand (COD) and biopolymers solubilization, AD bioenergy production, input electrical energy, and overall net energy production of the sequential pretreatment/AD process. The heating applicators for the bench-scale testing consisted of a custom-built pressure-sealed heating vessel for CH experiments, an off-the-shelf programmable MW oven operating at a frequency of 2.45 GHz for MW heating experiments, and a newly developed 1 kW RF heating system operating at a frequency of 13.56 MHz for RF heating experiments. Under identical thermal profiles, all three thermal pretreatment methods achieved similar sludge disintegration in terms of COD and biopolymer solubilization as well as AD bioenergy production (p-value > 0.05). According to the energy assessment results, the application of CH and MW pretreatments resulted in overall negative energy production, while positive net energy production was obtained through the sequential pretreatment/AD process utilizing RF pretreatment.

Using mass struvite precipitation to remove recalcitrant nutrients and micropollutants from anaerobic digestion dewatering centrate.

The primary objective of this research was to remove recalcitrant nutrients from anaerobically digested sludge dewatering centrate. A struvite precipitation methodology is proposed where salt crystals are encouraged to ballast colloidal particles through heterogeneous nucleation and subsequent crystal growth. The secondary objective was to assess presence of micropollutants in precipitates. Four biologically unique dewatering centrates were used to test the precipitation methodology on the variety of anaerobic digester configurations that can be expected from municipal wastewater treatment plant. The effect of digestion sludge retention time (2 day, 20 day) and digestion temperature (35 °C, 55 °C) on the removal of dissolved unreactive phosphorus (P) and nitrogen (N) was monitored. Averaged across all four centrates, the precipitation methodology resulted in dissolved unreactive P and N removal of 82.4% and 66.6%, respectively. Antimicrobial contaminants (triclosan, triclocarban) were observed in the precipitates at minute concentrations (<18 ng/g-dry solids). Therefore, mass struvite precipitation can provide a means of recalcitrant nutrient treatment and reactive nutrient recovery without the micropollutant burden of biosolids land application.

Advanced anaerobic digestion of municipal sludge using a novel and energy-efficient radio frequency pretreatment system.

Microwave (MW) sludge pretreatment systems are usually limited to a frequency of 2.45 GHz and the heating frequency is constrained by commercially available hardware. Studies using MW heating at this frequency have reported negative net energy balance (output energy as methane minus input electrical energy). This necessitates further research into more efficient thermal pretreatment technologies. In this research, a novel and highly efficient radio frequency (RF) pretreatment system at a frequency of 13.56 MHz was designed, implemented, and tested for the first time. The system was custom-designed based on the dielectric characteristics of thickened waste activated sludge (TWAS) to achieve a very efficient and uniform heating system. The effects of three factors including pretreatment method (RF vs. MW), final temperature (60, 90 and 120 °C), and stationary (holding) time (0, 1 and 2 h) on sludge solubilization and performance of mesophilic batch anaerobic digestion were evaluated simultaneously. Energy measurements were also made to compare the efficiency of the custom-designed RF and conventional MW heating systems. The differences in sludge disintegration (solubilization) using the RF and MW pretreatment systems were negligible (P > 0.05). No statistically significant difference was also observed between the two pretreatment systems in terms of mesophilic biogas production rate and extent (P > 0.05). The energy efficiency of the RF pretreatment system was measured between 67.3 and 95.5% for the temperature range of 25-120 °C which was significantly higher than that of the MW system efficiency which varied from 37 to 43%. Overall, the average input energy of the RF system was less than half of the energy consumed during the operation of the MW system to achieve a same target temperature. Considering the results of this research, the RF heating at a frequency of 13.56 MHz is suggested as an effective and energy-efficient technique for thermal hydrolysis of TWAS.

Conventional heating vs. microwave sludge pretreatment comparison under identical heating/cooling profiles for thermophilic advanced anaerobic digestion.

This research evaluates whether there is any advantage of selecting one of the thermal methods of sludge pretreatment, conventional heating (CH) and microwave hydrolysis (MW), over another to enhance municipal sludge disintegration and performance of thermophilic anaerobic digestion (AD). For this purpose, a custom-built CH system simulating MW hydrolysis under identical heating and cooling profiles was used. The effects of three main pretreatment parameters including pretreatment method (CH and MW), heating ramp rate (3, 6 and 11°C/min) and final temperature (80, 120 and 160°C) on sludge solubilization and performance of thermophilic batch AD were evaluated. The effects of CH and MW hydrolysis were observed to be similar for sludge disintegration and digester performance (p-value>0.05), while the effects of final temperature and heating ramp rate were proven to be different (p-value<0.05). According to the results, it is essential to apply MW and CH pretreatments under identical experimental condition for an unbiased comparison which supports the findings of the author's earlier study under mesophilic condition. Failing to address this issue explains the significant inconsistency observed among the findings of the previous CH vs. MW comparison studies that were unable to implement identical thermal profiles (between CH and MW) during sludge pretreatment. In comparison with mesophilic AD, thermophilic AD revealed lower biodegradation rate constant at the highest pretreatment temperature tested (160°C), suggesting its higher sensitivity to the inhibitory effects of thermal pretreatment at the elevated temperatures.

Collaborative case conferences in rectal cancer: case series in a tertiary care centre.

BACKGROUND: In many hospitals, resource barriers preclude the use of preoperative multidisciplinary cancer conferences (mccs) for consecutive patients with cancer. Collaborative cancer conferences (cccs) are modified mccs that might overcome such barriers. METHODS: We established a ccc at an academic tertiary care centre to review preoperative plans for patients with rectal cancer. Attendees included only surgeons who perform colorectal cancer procedures and a radiologist with expertise in cross-sectional imaging. Individual reviews began with the primary surgeon presenting the case information and initial treatment recommendations. Cross-sectional images were then reviewed, the case was discussed, and consensus on ccc-treatment recommendations was achieved. Outcomes for the present study were changes in treatment recommendations defined as "major" (that is, redirection of patient to preoperative radiation from straight-to-surgery or uncertain plan, or redirection of the patient to straight-to-surgery from preoperative radiation or plan uncertain) or as "minor" (that is, referral to a multidisciplinary cancer clinic, request additional tests, change type of neoadjuvant therapy, change type of surgery). Chart reviews provided relevant patient, tumour, and treatment information. RESULTS: Between September 2011 and September 2012, 101 rectal cancer patients were discussed at a ccc. Of the 35 management plans (34.7%) that were changed as a result, 8 had major changes, and 27 had minor changes. Available patient and tumour factors did not predict for a change in treatment recommendation. CONCLUSIONS: Preoperative cccs at a tertiary-care centre changed treatment recommendations for one third of patients with rectal cancer. Given that no specific factor predicted for a treatment plan change, it is likely prudent that all rectal cancer patients undergo some form of collaborative review.

Biodegradation and chemical precipitation of dissolved nutrients in anaerobically digested sludge dewatering centrate.

The objective of this research was to assess specific side-stream treatment processes for biodegradation and precipitation of dissolved nutrients in dewatering centrate. In this study, characterization was made of a conventional suspended growth deammonification treatment process for transforming dissolved polyphosphate (poly-P), dissolved organic phosphorus (DOP) and dissolved organic nitrogen (DON) in two types of dewatering centrate. The deammonification process was configured as a sequencing batch reactor (SBR), combining partial nitrification and anaerobic ammonia oxidation (anammox) in a single tank. The first centrate feed studied was from the full-scale Annacis Island wastewater treatment plant (AIWWTP) located in Metro Vancouver, Canada. The second centrate feed was from a lab-scale anaerobic digester (AD) fed waste sludge from the existing City of Kelowna Wastewater Treatment Facility (KWTF), located in the Okanagan Valley, Canada. In addition, poly aluminum chloride (PACL) dosing was assessed for final polishing of dissolved nutrients. The deammonification SBR (DeSBR) process showed similar treatment characteristics for both the KWTF and AIWWTP centrates with excellent DON removal and poor non-reactive dissolved phosphorus (NRDP) removal. A statistical comparison of the DOP and poly-P through the DeSBR process suggests that DOP has a higher biodegradation potential. Future research focused on understanding the variables associated with degradation of DOP could lead to better NRDP removal through deammonification processes. Utilization of a post-anammox PACL chemical dosing stage can achieve the objective of precipitating any residual DON and NRDP and producing an effluent that has lower dissolved nutrients than the pre-digestion KWTF dewatering centrate scenario.

Health risk assessment of heavy metals through the consumption of food crops fertilized by biosolids: A probabilistic-based analysis.

The objective of this study was to perform a probabilistic risk analysis (PRA) to assess the health risk of Cadmium (Cd), Copper (Cu), and Zinc (Zn) through the consumption of food crops grown on farm lands fertilized by biosolids. The risk analysis was conducted using 8 years of historical heavy metal data (2005-2013) of the municipal biosolids generated by a nearby treatment facility considering one-time and long-term biosolids land application scenarios for a range of 5-100 t/ha fertilizer application rate. The 95th percentile of the hazard index (HI) increased from 0.124 to 0.179 when the rate of fertilizer application increased from 5 to 100 t/ha at one-time biosolids land application. The HI at long-term biosolids land application was also found 1.3 and 1.9 times greater than that of one-time land application at fertilizer application rates of 5 and 100 t/ha, respectively. Rice ingestion had more contribution to the HI than vegetable ingestion. Cd and Cu were also found to have more contribution to the health risk associated to vegetable and rice ingestion, respectively. Results indicated no potential risk to the human health even at long-term biosolids land application scenario at 100 t/ha fertilizer application rate.

Below and above boiling point comparison of microwave irradiation and conductive heating for municipal sludge digestion under identical heating/cooling profiles.

This research provides a comprehensive comparison between microwave (MW) and conductive heating (CH) sludge pretreatments under identical heating/cooling profiles at below and above boiling point temperatures. Previous comparison studies were constrained to an uncontrolled or a single heating rate due to lack of a CH equipment simulating MW under identical thermal profiles. In this research, a novel custom-built pressure-sealed vessel which could simulate MW pretreatment under identical heating/cooling profiles was used for CH pretreatment. No statistically significant difference was proven between MW and CH pretreatments in terms of sludge solubilization, anaerobic biogas yield and organics biodegradation rate (p-value>0.05), while statistically significant effects of temperature and heating rate were observed (p-value<0.05). These results explain the contradictory results of previous studies in which only the final temperature (not heating/cooling rates) was controlled.

Anaerobic co-digestion of wine/fruit-juice production waste with landfill leachate diluted municipal sludge cake under semi-continuous flow operation.

Anaerobic co-digestion of four organic waste streams; a thickened waste activated sludge (TWAS) and screen cake (SC) from a fruit-juice/winery wastewater treatment plant along with municipal sludge cake (MC) and landfill leachate (LL) was evaluated. A total of eight semi-continuously-fed single and co-digesters were operated side-by-side at sludge retention times (SRT) of 20 and 10 days. Co-digestion of industrial waste streams (TWAS and SC) with MC and LL resulted in increased operational stability compared to the single digestion of industrial TWAS at the higher organic loading (10 d SRT). Although digester operational temperature had no statistically significant effect on organics removal and biogas production, mesophilic digesters had consistently higher total coliform densities (8838-37,959 most probable number or MPN/g-dry weight) compared to the thermophilic digesters (41-6723 MPN/g-dry weight) at both SRTs. Coliform analysis results also proved that most of the thermophilic digestates could be classified as Class A biosolids according to regulations. Furthermore, addition of industrial TWAS to co-digesters enhanced the dewaterability of the digested streams. A cost-benefit analysis confirmed the benefits and indicated that a full-scale co-digester utilizing all four waste streams can decrease the total capital and operational cost by 22% ($10.52 million).

Mesophilic batch anaerobic co-digestion of fruit-juice industrial waste and municipal waste sludge: process and cost-benefit analysis.

The feasibility of anaerobic co-digestion of two juice-based beverage industrial wastes, screen cake (SC) and thickened waste activated sludge (TWAS), along with municipal sludge cake (MC) was investigated. Experiments were conducted in twenty mesophilic batch 160 ml serum bottles with no inhibition occurred. The statistical analysis proved that the substrate type had statistically significant effect on both ultimate biogas and methane yields (P=0.0003<0.05). The maximum and minimum ultimate cumulative methane yields were 890.90 and 308.34 mL/g-VSremoved from the digesters containing only TWAS and SC as substrate. First-order reaction model well described VS utilization in all digesters. The first 2-day and 10-day specific biodegradation rate constants were statistically higher in the digesters containing SC (P=0.004<0.05) and MC (P=0.0005<0.05), respectively. The cost-benefit analysis showed that the capital, operating and total costs can be decreased by 21.5%, 29.8% and 27.6%, respectively using a co-digester rather than two separate digesters.

Application of the International Water Association activated sludge models to describe aerobic sludge digestion.

Batch and semi-continuous flow aerobic digesters were used to stabilize thickened waste-activated sludge at different initial conditions and mean solids retention times. Under dynamic conditions, total suspended solids, volatile suspended solids (VSS) and total and particulate chemical oxygen demand (COD and PCOD) were monitored in the batch reactors and effluent from the semi-continuous flow reactors. Activated Sludge Model (ASM) no. 1 and ASM no. 3 were applied to measured data (calibration data set) to evaluate the consistency and performances of models at different flow regimes for digester COD and VSS modelling. The results indicated that both ASM1 and ASM3 predicted digester COD, VSS and PCOD concentrations well (R2, Ra2 > or = 0.93). Parameter estimation concluded that compared to ASM1, ASM3 parameters were more consistent across different batch and semi-continuous flow runs with different operating conditions. Model validation on a data set independent from the calibration data successfully predicted digester COD (R2 = 0.88) and VSS (R2 = 0.94) concentrations by ASM3, while ASM1 overestimated both reactor COD (R2 = 0.74) and VSS concentrations (R2 = 0.79) after 15 days of aerobic batch digestion.

Qualitative assessment of patient experiences following sacrectomy.

BACKGROUND AND OBJECTIVES: The primary objective was to investigate patient experiences following sacral resection as a component of curative surgery for advanced rectal cancers, soft tissue and bone sarcomas. METHODS: Qualitative methods were used to examine the experiences, decision-making, quality of life, and supportive care needs of patients undergoing sacrectomy. Patients were identified from two prospective databases between 1999 and 2007. A semi-structured interview guide was generated and piloted. Patient interviews were transcribed verbatim and analyzed using standard qualitative research methodology. Grounded theory guided the generation of the interview guide and analysis. RESULTS: Twelve patients were interviewed (6 female, 32-82 years of age). The mean interview time was 34 min. Five themes were identified, including: (1) the life-changing impact of surgery on both patients' and their family's lives, (2) patient satisfaction with immediate care in hospital, (3) significant chronic pain related to sacrectomy, (4) patients' need for additional information regarding long-term recovery, and (5) patients' gratitude to be alive. CONCLUSIONS: Sacrectomy is a life-changing event for patients and their families. Patients undergoing sacrectomy need further information regarding the long-term consequences of this procedure. This need should be addressed in both preoperative multi-disciplinary consultations and at follow-up visits.

Meta-analysis of randomized controlled trials comparing open and laparoscopic ventral and incisional hernia repair with mesh.

BACKGROUND: Laparoscopic ventral and incisional hernia repair has been reported in a number of small trials to have equivalent or superior outcomes to open repair. METHODS: Randomized controlled trials comparing laparoscopic and open incisional or ventral hernia repair with mesh that included data on effectiveness and safety were included in a meta-analysis. RESULTS: Eight studies met the inclusion criteria. There was no difference between groups in hernia recurrence rates (relative risk 1.02 (95 per cent confidence interval (c.i.) 0.41 to 2.54)). Duration of surgery varied. Mean length of hospital stay was shorter after laparoscopic repair in six of the included studies; the longest mean stay was 5.7 days for laparoscopic and 10 days for open surgery. Laparoscopic hernia repair was associated with fewer wound infections (relative risk 0.22 (95 per cent c.i. 0.09 to 0.54)), and a trend toward fewer haemorrhagic complications and infections requiring mesh removal. CONCLUSION: Laparoscopic repair of ventral and incisional hernia is at least as effective, if not superior to, the open approach in a number of outcomes.

Assessment of physiological state of microorganisms in activated sludge with flow cytometry: application for monitoring sludge production minimization.

Many sludge reduction processes have been studied for the minimization of sludge production in biological wastewater treatment. The investigations on most of these processes have monitored the increase of the soluble chemical oxygen demand, the sludge mass reduction, or the decrease of the floc size, but little information has been obtained on cell lysis and the change of the biological cell activity. However, employing any strategy for reducing sludge production may have an impact of microbial community in biological wastewater treatment process. This impact may influence the sludge characteristics and the quality of effluent. The objective of this study concerns the determination of the physiological state of activated sludge microorganisms during a sludge minimization process. A thermal treatment at 80 degrees C for 5, 20, 40 and 60 min was chosen in this study. Staining bacteria with CTC and SYTOX green was used to evaluate biological cell activity and viability of cell types contained in activated sludge, respectively. The monitoring of cell activity and viability was performed using flow cytometry (FCM) analysis before and after thermal treatment of activated sludge. Results indicated an increase in the number of permeabilized cells and a decrease in the number of active cells, subsequent to the thermal treatment. The study also confirms the potential of FCM to successfully evaluate the physiological heterogeneity of an activated sludge bacterial population. Moreover, the experimentally observed correlations between the FCM results and the organic matter solubilization in activated sludge samples during thermal treatment revealed that the increase in the soluble organic matter concentration was predominantly due to an intracellular material release. Identifying the increase in activated sludge hydrolysis requires a precise knowledge of the involved mechanisms, and this study indicated that the FCM, used in conjunction with specific probes, could be a useful tool.

Initial examination of microwave pretreatment on primary, secondary and mixed sludges before and after anaerobic digestion.

The effects of microwave pretreatment on disintegration and mesophilic digestion of waste activated sludge (WAS), primary sludge (PS), combined (PS + WAS) sequencing batch reactor (SBR) sludge and anaerobically digested biocake were investigated by both household and bench scale industrial types microwaves at temperatures below and above boiling point. Pretreatment variables, temperature, intensity (cooking rate) and sludge concentration had statistically significant effects on solubilization. The microwave pretreatment also increased the bioavailability of sludge components under batch anaerobic digestion and enhanced the dewaterability of pretreated sludges after digestion. However, the level of improvements in solubilization and biodegradation from different waste sludges were different. While the largest improvement in ultimate biodegradation was observed in WAS, microwave irradiation only affected the rate of biodegradation of pretreated PS samples. Similarly, relatively lower solubilization ratios achieved for combined - SBR sludge was attributed to high sludge age of extended aeration SBR unit. It is possible that initial sludge characteristics may influence final pretreatment outcomes so that general statements of performance cannot always be made.