Experimental investigation of earth-air heat exchanger using porous clay vessels for eco-friendly buildings.

This study introduces an experimental investigation of a novel direct trend evaporative cooler based on a ground-air heat exchanger (GAHE) using porous clay vessels as an evaporation media under a variety of operational conditions, including air flow rate, inlet air temperature, temperature of inlet water, and in air humidity. The evaluation of the GAHE performance was based on the air-cooling effect, wet-bulb and dew-point efficiencies, energy efficiency ratio, water evaporation rate, specific water evaporation, specific cooling capacity, specific total cost, and CO2 emission rate. The influences of dry-bulb temperature, the incoming air's relative humidity (RH), and six air flow rates ranging from 11 to 25 L/s on the performance are investigated and discussed. Results indicated that increasing the air flow rate leads to an increase in the cooling capacity. Energy efficiency ratio (EER) reaches the highest value of about 25.5 recorded at 3:00 PM with air flow rate = 11 L/s. The lowest EER value is approximately 7.2 when the measured inlet and outlet temperatures are the closest at 7:00 PM, with a flow rate of 25 L/s. Increasing the air flow rate from 11 to 17 L/s increased the wet bulb efficiency, and the airflow rate was inversely proportional to wet-bulb efficiency. The maximum and minimum average dew-point efficiencies are 64% and 58% at 17 L/s and 22 L/s respectively. The water evaporation rate increases by 182.1%, increasing the air flow rate from 11 to 25 L/s.

Formulation of Saxagliptin Oral Films: Optimization, Physicochemical Characterization, In-Vivo Assessment, and In-Vitro Real-Time Release Monitoring via a Novel Polyaniline Nanoparticles-Based Solid-Contact Screen Printed Ion-Selective Electrode.

Oral dispersible films have received broad interest due to fast drug absorption and no first-path metabolism, leading to high bioavailability and better patient compliance. Saxagliptin (SXG) is an antidiabetic drug that undergoes first-path metabolism, resulting in a less active metabolite, so the development of SXG oral dispersible films (SXG-ODFs) improves SXG bioavailability. The formula optimisation included a response surface experimental design and the impact of three formulation factors, the type and concentration of polymer and plasticiser concentration on in-vitro disintegration time and folding endurance. Two optimised SXG-ODFs prepared using either polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose were investigated. SXG-ODFs prepared with PVA demonstrated a superior rapid disintegration time, ranging from 17 to 890 s, with the fastest disintegration time recorded at 17 s. These short durations can be attributed to the hydrophilic nature of PVA, facilitating rapid hydration and disintegration upon contact with saliva. Additionally, PVA-based films displayed remarkable folding endurance, surpassing 200 folds without rupture, indicating flexibility and stability. The high tensile strength of PVA-based films further underscores their robust mechanical properties, with tensile strength values reaching up to 4.53 MPa. SXG exhibits a UV absorption wavelength of around 212 nm, posing challenges for traditional quantitative spectrophotometric analysis, so a polyaniline nanoparticles-based solid-contact screen-printed ion-selective electrode (SP-ISE) was employed for the determination of SXG release profile effectively in comparison to HPLC. SP-ISE showed a better real-time release profile of SXG-ODFs, and the optimised formula showed lower blood glucose levels than commercial tablets.

Infrared diode laser enhances human periodontal ligament stem cells behaviour on titanium dental implants.

Low level laser treatment (LLLT) is known for its photobiostimulatory and photobiomodulatory characteristics, which stimulate cell proliferation, increase cellular metabolism, and improve cellular regeneration. The objective of the present research was to assess the possible influence of infrared diode laser irradiation on the behaviour, attachment, and osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) seeded on different types of dental implants. Two distinct types of implants, one subjected to laser surface treatment and the other treated with acid etching, were longitudinally divided into two halves and submerged in six wells culture plates. Both implants were subjected to infrared diode laser treatment, and subsequently, the morphology and attachment of cells were examined using scanning electron microscopy (SEM) after 14 and 21 days. The behaviour of (hPDLSCs) towards two types of implants, when exposed to osteogenic medium and low-level laser therapy (LLLT), was assessed using quantitative real-time polymerase chain reaction to measure the expression of stemness markers and osteogenic markers. The scanning electron microscopy (SEM) demonstrated that the application of infrared diode laser irradiation substantially improved the attachment of cells to both types of implants. The stemness gene markers were significantly down regulated in cells seeded on both surfaces when challenged with osteogenic media in relation to control. At 14 days, early osteogenic markers, were upregulated, while late osteogenic markers, were downregulated in both challenged groups. At the 21-day mark, hPDLSCs seeded on an acid-etched implant exhibited increased expression of all osteogenic markers in response to stimulation with osteogenic media and infra-red diode laser, in contrast to hPDLSCs seeded on a laser surface treated implant under the same conditions. Finally, the findings of our research revealed that when subjected to infrared diode laser, human periodontal ligament stem cells cultured on both types of implants demonstrated improved cellular attachment and differentiation. This suggested that infrared diode laser enhanced the activity of the cells surrounding the implants. Hence, the use of infrared diode laser could be pivotal in improving and expediting the clinical osseointegration process around dental implants.

Impact of Pretransplant Dialysis Modality on Posttransplant Outcomes: A Single-Center Experience.

OBJECTIVES: It remains unclear whether posttransplant outcomes differ according to the pretransplant dialysis modality (peritoneal dialysis vs hemodialysis). Our aim was to assess posttransplant outcomes in patients with different predialysis modalities. MATERIALS AND METHODS: Two thousand two hundred fifty-eight kidney recipients following up in Hamed Alessa Organ transplant center in Kuwait were included and divided into two groups according to pre-transplant dialysis modality: Group 1: those who received hemodialysis (HD) and group 2: those with peritoneal dialysis (PD). Demographics, pretransplant and posttransplant comorbidities, and patient and graft outcomes were studied. RESULTS: There were 1956 patients on hemodialysis, and 302 patients were on peritoneal dialysis. Most were male patients (1456 vs 802 female patients), with comparable mean age (P = .34). Chronic glomerulonephritis and diabetic nephropathy represented the most common original kidney disease before transplant (27.6% and 21.4%, respectively), with higher prevalence of glomerulonephritis in group 1 and diabetic nephropathy in group 2 (P = .001). The 2 groups were comparable with regard to immunosuppression (induction and maintenance) (P > .05). Posttransplant diabetes and hypertension were significantly higher in the hemodialysis group (P = .004 and P = 003, respectively). There was no significant difference between the 2 groups with regard to the graft outcome (P = .86). However, patient survival was significantly higher in the hemodialysis group (81.2% vs 64.4%). CONCLUSIONS: Compared with peritoneal dialysis, pretransplant hemodialysis is associated with better posttransplant patient survival despite no difference in the graft outcome. Diabetes-related complications could be attributed to such outcomes.

Towards an Effective Service Allocation in Fog Computing.

The Internet of Things (IoT) generates a large volume of data whenever devices are interconnected and exchange data across a network. Consequently, a variety of services with diverse needs arises, including capacity requirements, data quality, and latency demands. These services operate on fog computing devices, which are limited in power and bandwidth compared to the cloud. The primary challenge lies in determining the optimal location for service implementation: in the fog, in the cloud, or in a hybrid setup. This paper introduces an efficient allocation technique that moves processing closer to the network's fog side. It explores the optimal allocation of devices and services while maintaining resource utilization within an IoT architecture. The paper also examines the significance of allocating services to devices and optimizing resource utilization in fog computing. In IoT scenarios, where a wide range of services and devices coexist, it becomes crucial to effectively assign services to devices. We propose priority-based service allocation (PSA) and sort-based service allocation (SSA) techniques, which are employed to determine the optimal order for the utilizing devices to perform different services. Experimental results demonstrate that our proposed technique reduces data communication over the network by 88%, which is achieved by allocating most services locally in the fog. We increased the distribution of services to fog devices by 96%, while simultaneously minimizing the wastage of fog resources.

Urethral Plate Substitution in Two-Stage Hypospadias Repair: Grafts Versus Flaps.

BACKGROUND: Choosing between flaps or grafts to substitute the urethral plate in 2-stage hypospadias repair has been a matter of debate with no consensus in the literature. Flaps have reliable blood supply that maybe theoretically less liable for strictures or contractures. Grafts are more versatile, which can be used in primary and recurrent cases when healthy local skin is deficient.In this report, our aim was to compare outcomes of grafts and flaps when used to substitute the urethral plate in two-stage repair of primary proximal hypospadias with ventral curvature. METHODS: This retrospective study included primary cases of hypospadias with significant curvature who underwent two-stage repair using either grafts or flaps to substitute the urethral plate in the first stage. Cases included in the study were divided into two groups according to the technique of substituting the urethral plate at the first stage of repair. During first part of the study period (2015 through 2018), we mostly used grafts to substitute the urethral plate (group A); later, we shifted to skin flaps (Group B) during the period 2019 through 2021. RESULTS: The study included 37 boys with primary proximal hypospadias who underwent two-stage hypospadias repair. The meatus position was penoscrotal in 18, scrotal in 16, and perineal in three. Inner preputial graft was used to substitute the urethral plate in 18 cases (group A), while dorsal skin flaps were used in 19 (group B). Out of the 37 cases, 27 were available at follow-up after second stage (group A = 14; group B = 13). Follow up period ranged between 6 and 42 months (mean 19.7; median 18.5). Overall, 14 cases required reoperations for different indications: partial disruptions of distal part of the repair in six, closure of urethro-cutaneous fistula in six, and urethral strictures in two. The rate of complications was higher in group A (10 cases: 71%) compared to group B (4 cases: 31%) (Fisher exact test, p-value = 0.057). CONCLUSION: Grafts were associated with higher complication rate than flaps when used to substitute the urethral plate in two-stage repair of proximal hypospadias with chordee. TYPE OF STUDY AND LEVEL OF EVIDENCE: This is non-randomized comparative study (level III evidence).

Autologous platelet gel improves outcomes in tubularized incised plate repair of hypospadias.

BACKGROUND: hypospadias is one of the most widespread male congenital anomalies, occurring in 1:250 to 1:300 live births. Several repair techniques have been developing to improve the outcomes. PURPOSE: a randomized prospective controlled study was adopted to evaluate effectiveness of autologous platelet gel in healing promotion and improving the outcomes of hypospadias repair. METHODS: thirty children who aged between 6 months and 12 years were recruited and subdivided into two groups; group A had tubularized incised plate (TIP) repair with autologous platelet gel application and group B had TIP repair without autologous platelet gel. RESULTS: there was no significant difference in duration of operation between both groups. All patients in groups A and B had slit-like meatus shape in the distal glans. While all those of group A had one urine stream, yet only 11 of group B had one. There were complications that happened exclusively in group B such as spray stream (27%) and fistula (20%). Whereas other complications occurred insignificantly more in group B than in A including meatal stenosis (53 versus 27%), glans dehiscence, (20 versus 7%), bleeding (33 versus 13%), infection (33 versus 27%), edema (27% versus13), respectively. The incidence of skin necrosis was equal in both groups. CONCLUSION: autologous platelet gel usage in TIP hypospadias repair can be a reliable technique to promote wound healing, and to limit of postoperative surgical complications.

Immobilized algae-based treatment of herbicide-contaminated groundwater.

Scenedesmus species, immobilized on alginate gel, was found effective in removing nitrate, atrazine, magnesium, phosphorus, zinc, oxadiazon, and triallate from groundwater in a continuous flow reactor. The laboratory-scale experiments with synthetic groundwater, made of 8.8 mg/L NO3 -N and 90 µg/L atrazine, were performed at a hydraulic retention time of 7 days and the temperatures of 20 and 35°C. The highest uptake of nitrate and atrazine was observed at 20°C (97% and 70%, respectively). When tested in actual groundwater, 92% of nitrate, 100% of magnesium, 99.9% of phosphorus, and 92% of zinc were successfully removed at the end of 29 days' treatment operations. The algal beads removed 100% of oxadiazon and triallate in the first 10 days, but some of the herbicides diffused back into the solution toward the end of the treatment process. PRACTITIONER POINTS: Immobilized algae-alginate beads can remove nitrate, atrazine, oxadiazon, and triallate from groundwater in continuous flow reactor. The uptake rate of nitrate and atrazine is higher in room temperature (20°C). Same algae beads could be reused for herbicide uptake for the average of 10 days. The immobilized system is a natural sustainable alternative that can be used in groundwater pump and treat.

Sirolimus: A Rescue Drug to Control Complications of Extensive Venous Malformation.

Venous malformations represent a major sector of vascular anomalies. Most cases are asymptomatic or subclinical; however, large extensive lesions can cause severe disability and sometimes mortality. In this report, we present a successful case of sirolimus treatment in managing an extensive venous malformation in the pelvis of a 21-month-old boy who presented with life-threatening complications. With a history dating since the day 2 of life, the patient suffered from chronic bleeding due to scrotal skin ulcerations, in addition to recurrent attacks of severe bleeding per rectum necessitating hospital admission and blood transfusion (three attacks since the age of 7 months). Pelvic magnetic resonance image showed the typical findings of extensive venous malformation involving the pelvis, perineum, scrotum, and extending to the gluteal region. The lesion was seen totally encasing the anorectum with marked thickening of their walls almost occluding their lumen. Oral sirolimus (2 mg/m 2 ) was started with a target blood trough level of 5 to 10 ng/mL. Over a follow-up period of 5 months, there was obvious clinical improvement that included healing of skin lesions (scrotal ulcer) with complete re-epithelialization, absence of bleeding per rectum with improvement of constipation, and rise of hemoglobin level from 7.5 to 11.5 g/dL.

How far can one-stage laparoscopic Fowler-Stephens orchiopexy be implemented in intra-abdominal testes with short spermatic vessels?

OBJECTIVE: The aim of the study was to compare the outcome of the prospective cohort who had one-stage laparoscopic Fowler-Stephens orchiopexy (LFSO) with an earlier, similar cohort who had a two-stage LFSO. Both cohorts included only intra-abdominal testes (IATs) with short spermatic vessels. STUDY DESIGN: The present study initially included all patients between the age of six months and preschool age, presenting with an IAT to the authors' tertiary clinic from January 2012 to December 2014. Only intra-abdominal testes with short testicular vessels, correlating to type 3A, 3B and 4A as per the updated Ain Shams classification, were included in this study. One-stage LFSO was performed on all patients. Patients with bilateral intra-abdominal testes had the procedure performed on the contralateral side 6-8 weeks later. Follow-up was performed at 6, 12 and 36 months postoperatively by means of Doppler ultrasound in the first two visits. A similar subgroup of the historical cohort from years 2002 to 2010 had a two-stage LFSO, with the second stage being performed 12-16 weeks later. In bilateral cases, a three-interval surgery based on two-stage LFSO was performed, with a follow-up at 6 months postoperatively. RESULTS: The recent cohort included 16 IATs (10 unilateral and 3 bilateral). The median age of the patients was 1.41 years. At 6-month follow-up, 4 testes were found atrophic (25%), whereas the remaining 12 testes (75%) were viable. In those viable, only half of them had a low scrotal position. No difference was found at 12- or 36-month follow-up. Doppler ultrasound confirmed adequate intratesticular blood flow at 6 and 12 months postoperatively. In the similar subgroup of the historical cohort, 3 of 25 (12%) testes were found atrophied at six months postoperatively, with only one testis (4%) having a high scrotal position. In a comparison of both cohorts, the two-stage LFSO was found to be associated with a halving of the testicular atrophy rate (p value = 0.401) and a higher incidence of low scrotal position (p value = 0.004). A comparison of both cohorts is shown in the summary table. CONCLUSION: Although one-stage LFSO may seem tempting, it still holds a higher rate of testicular atrophy, which is not justified. LEVEL OF EVIDENCE: Level III (Case-control study).

An Optimized Load Balance Solution for Multi-homed Host in Heterogeneous Wireless Networks.

The imminent wireless technologies are demanding fusion of several networks with diverse technologies. A convenient user device for such an environment is the multihomed host, which is capable of making use of simultaneous multiple connections of heterogeneous networks and smartly distributing/receiving data among them. The aim of this work is to develop a mechanism for assessing the multihoming concept and to propose a system model for increasing its applicability. The proposed model provided a novel user-centric scheme for multihoming for multi-radio access technologies (multi-RAT). It is considered an evolution of traffic offloading for gaining more capacity, higher data rates, and real-time services. This work assumes data classifications, evaluates and ranks the available connections, and utilizes the application data in an unequal load balance scheme. This is achieved by analyzing the performance of three of the most widely used alternative-choice for multiple attributes decision making (MADM) methods. The analytical hierarchy process (AHP), along with a utility equation, is applied to the system model for unequal load balance solution. The proposed model is targeting an energy efficient mechanism which satisfies application needs. Moreover, it reveals an efficient transmission mechanism for a better quality of service, traffic management, and availability solutions. The simulation results show that the proposed system surpassed its former counterparts.

Role of Diabetes Education Program in Controlling Posttransplant Diabetes in a Recent Renal Transplant Bodybuilder: Case Report and Review of the Literature.

Posttransplant diabetes is a common complication of solid-organ transplantation. We present the possible role of diabetes education in improvement of posttransplant diabetes in a 36-year-old bodybuilder who was a kidney transplant recipient. The patient had been abusing some medications to help in bodybuilding. He underwent living unrelated-donor renal transplant with thymoglobulin induction and was maintained on steroids, tacrolimus, and mycophenolate mofetil. Posttransplant diabetes was confirmed by blood tests. His blood sugar was partially controlled by 3 oral agents. The patient participated in our structured diabetes education program. This program was created to cover different items related to diabetes control, including diet, proper exercise, blood sugar monitoring, sick day management, and pathophysiologic roles of diabetes medications. Within 4 months of participation in this program, the patient's blood sugar became well controlled and his diabetes medications started to be minimized. He presently has stable graft function with hemoglobin A1c level around 5.6% on only diet management. Bodybuilders are at risk of deterioration of their kidney function. A proper diabetes education program is recommended to help renal transplant recipients with early posttransplant diabetes mellitus to control their disease. Success requires close evaluation and a multidisciplinary approach.

Benchmarking the Energy Intensity of Small Water Resource Recovery Facilities.

To enable small communities to benchmark the energy efficiency of their water resource recovery facilities (also known as wastewater treatment facilities), multiple linear regression models of electric and overall energy intensity (kWh/m3) were created using data from Nebraska and Pennsylvania. Key variables found to be significant include: facility type, supplemental energy usage for sludge treatment, average flow, percent design flow, climate controlled floor area, effluent NH3-N, and influent CBOD5. The results show that energy use models for small systems differ from those for large facilities and that regulatory changes can affect energy usage. Step changes in the data for facilities that changed operators highlight the importance of operational decisions on energy efficiency for small facilities serving fewer than 10,000 people. Differences were observed between the models of data from specific states. Although these models may not include all factors that account for variability in energy use, they can provide a reference benchmark for small WRRFs.

Mortality prediction after cardiac surgery: blood lactate is indispensible.

BACKGROUND: Blood lactate is accepted as a mortality risk marker in intensive care units (ICUs), especially after cardiac surgery. Unfortunately, most of the commonly used ICU risk stratification scoring systems did not include blood lactate as a variable. We hypothesized that blood lactate alone can predict the risk of mortality after cardiac surgery with an accuracy that is comparable to those of other complex models. We therefore evaluated its accuracy at mortality prediction and compared it with that of other widely used complex scoring models statistically. METHODS: We prospectively collected data of all consecutive adult patients who underwent cardiac surgery between January 1, 2007, and December 31, 2009. By using χ2 statistics, a blood lactate-based scale (LacScale) with only four cutoff points was constructed in a developmental set of patients (January 1, 2007, and May 31, 2008). LacScale included five categories: 0 (≤ 1.7 mmol/L); 1 (1.8-5.9 mmol/L), 2 (6.0-9.3 mmol/L), 3 (9.4-13.3 mmol/L), and 4 (≥ 13.4 mmol/L). Its accuracy at predicting ICU mortality was evaluated in another independent subset of patients (validation set, June 1, 2008, and December 31, 2009) on both study-population level (calibration analysis, overall correct classification) and individual-patient-risk level (discrimination analysis, ROC statistics). The results were then compared with those obtained from other widely used postoperative models in cardiac surgical ICUs (Sequential Organ Failure Assessment [SOFA] score, Simplified Acute Physiology Score II [SAPS II], and Acute Physiology and Chronic Health Evaluation II [APACHE II] score). RESULTS: ICU mortality was 5.8% in 4,054 patients. LacScale had a reliable calibration in the validation set (2,087 patients). It was highly accurate in predicting ICU mortality with an area under the ROC curve (area under curve [AUC]; discrimination) of 0.88. This AUC was significantly larger than that of all the other models (SOFA 0.83, SAPS II: 0.79 and APACHE II: 0.76) according to DeLong's comparison. Integrating the LacScale in those scores further improved their accuracy by increasing their AUCs (0.88, 0.81, and 0.80, respectively). This improvement was also highly significant. CONCLUSION: Blood lactate accurately predicts mortality at both individual patient risk and patient cohort levels. Its precision is higher than that of other commonly used "complex" scoring models. The proposed LacScale is a simple and highly reliable model. It can be used (at bedside without electronic calculation) as such or integrated in other models to increase their accuracy.

Efficacy of triamcinolone acetonide and bupivacaine for pain after lumbar discectomy.

The study is a prospective blinded randomised controlled trial to compare the efficacy of triamcinolone acetonide, bupivacaine or in combination in managing pain after lumbar discectomy. Patients undergoing primary single-level lumbar discectomy were randomised. Triamcinolone acetonide, bupivacaine or in combination was instilled at the nerve root as decompression. Preoperative, day 1 and 6 weeks pain score, 24-h postoperative opiate requirements and duration of inpatient stay were recorded. Data was analysed using Mann-Whitney test for statistical significance. 100 patients were recruited. A significant difference was noted in day one postoperative mean pain score, mean 24-h opiate requirement and mean inpatient stay in the triamcinolone acetonide and bupivacaine group. At 8 weeks postoperatively, no significant differences were seen in the pain score in all groups. Significant postoperative pain reduction and opiate requirements in the first 24 h, and significantly shortened duration of inpatient stay were achieved in the triamcinolone acetonide and bupivacaine group compared with other groups.

Ammonium oxidation via nitrite accumulation under limited oxygen concentration in sequencing batch reactors.

In this study, the effects of sludge retention time (SRT) on NH(4)-N oxidation and NO(x)-N accumulation in the nitritation reactors were studied. The gradually decrease of SRT also caused long reaction time to achieve 99% NH(4)-N removal. Although the target NH(4)-N removal was achieved in a short reaction time at 40 days of SRT, decreasing of SRT from 40 to 30, 25, 20 days, increase the reaction time from 168 to 240 and 265 h, respectively. The inlet NH(4)-N was almost oxidized and the concentration of NO(2)-N accumulated to a high level of 177 mg/l, while NO(2)-N/(NO(3)-N+NO(2)-N) ratio was about 0.9 at SRT of 40 days. However, the concentration of NO(3)-N increased slightly and NO(2)-N/(NO(x)-N) ratio dropped to 0.8 when the SRT was lower than 40 days. During the operation in a cycle, free ammonia concentration in the SBR was decreased from 2.8 to 0.7 mg/l which is below the lowest concentration causing inhibition of nitrite oxidizing bacteria (NOB). It was assumed that combined dissolved oxygen limitation and NH(3)-N inhibition on NOB caused NO(2)-N accumulation under the experimental conditions.

Nitritation and denitritation of ammonium-rich wastewater using fluidized-bed biofilm reactors.

Fluidized-bed biofilm nitritation and denitritation reactors (FBBNR and FBBDR) were operated to eliminate the high concentrations of nitrogen by nitritation and denitritation process. The dissolved oxygen (DO) concentration was varied from 1.5 to 2.5 g/m(3) at the top of the reactor throughout the experiment. NH(4)-N conversion and NO(2)-N accumulation in the nitritation reactor effluent was over 90 and 65%, respectively. The average NH(4)-N removal efficiency was 99.2 and 90.1% at the NLR of 0.9 and 1.2 kg NH(4)-N/m(3)day, respectively. Increasing the NLR from 1.1 to 1.2 kg NH(4)-N/m(3)day decreased the NH(4)-N elimination approximately two-fold while NH(4)-N conversion to NO(2)-N differences were negligible. The NO(2)-N/NO(x)-N ratios corresponded to 0.74, 0.73, 0.72, and 0.69, respectively, indicating the occurrence of partial nitrification. An average free ammonia concentration in the FBBNR was high enough to inhibit nitrite oxidizers selectively, and it seems to be a determining factor for NO(2)-N accumulation in the process. In the FBBDR, the NO(x)-N (NO(2)-N+NO(3)-N) concentrations supplied were between 227 and 330 mg N/l (NLR was between 0.08 and 0.4 kg/m(3)day) and the influent flow was increased as long as the total nitrogen removal was close to 90%. The NO(2)-N and NO(3)-N concentrations in the effluent were 3.0 and 0.9 mg/l at 0.08 kg/m(3)day loading rate. About 98% removal of NO(x)-N was achieved at the lowest NLR in the FBBDR. The FBBDR exhibited high nitrogen removal up to the NLR of 0.25 kg/m(3)day. The NO(x)-N effluent concentration never exceeded 15 mg/l. The total nitrogen removal efficiency in the FBBRs was higher than 93% at 21+/-1 degrees C.

Phosphorus fate and transport in soil columns loaded intermittently with influent of high phosphorus concentrations.

In this study, several columns of different lengths were filled with composite soils sampled from the field at corresponding depths and then loaded intermittently with influent of a high phosphorus concentration to evaluate phosphorus fate and transport in soil. The results indicate that the height of the mass transfer zone, solvent pore velocity, and soil's life expectancy for phosphorus removal increased with depth, while the retained phosphorus per kilogram of soil and the linear adsorption equilibrium coefficient, R, decreased with depth. An equation was developed to link liquid-phase phosphorus with solvent traveling time and soil depth. The results of X-ray diffraction and washout tests indicate that calcium-phosphorus precipitation and/or crystal growth occurred in the columns. The new protocol is useful for evaluation of phosphorus fate and transport in other subsurface systems, because it allows flexible adjustments in hydraulic loadings, feed solution, and sampling schemes.

Estimation of the intrinsic maximum substrate utilization rate using batch reactors with denitrifying biofilm: a proposed methodology.

A method for estimation of the maximum substrate utilization rate (q(max)) using batch reactors with denitrification biofilm was introduced and compared with the traditional method of using batch reactors with suspended growth for q(max) estimation. The values of q(max) obtained from the suspended-growth reactors (0.69 to 0.71 g N/g volatile suspended solids [VSS] x d) and from the attached-biomass reactors (0.74 to 0.85 g N/g VSS x d) are similar and within the range of the values reported in the literature (0.23 to 2.88 g N/g VSS x d). Therefore, the intrinsic kinetic parameter, q(max), can be obtained using attached-growth batch reactors, if the effectiveness factor, eta, is approximately equal to 1 and the bulk concentration of the rate-limiting substrate, C, is much higher than the half-velocity constant, K(S). The attached-growth batch reactor method is unique, because the biomass used in the batch tests is the same as that present in the parent reactor under investigation.

Effects of long-term wastewater application on chemical properties and phosphorus adsorption capacity in soils of a wastewater land treatment system.

The buildup of phosphorus (P) in the soil is a major factor limiting the operating life of a wastewater land treatment system. In this study, we evaluated changes of chemical properties, P profiles, and adsorption isotherms in the soils of a Muskegon wastewater land treatment system, which has received wastewater for approximately 30 years. It was found that the pH in the 15-cm topsoil increased from approximately 5-6 in 1973 to approximately 7.4-7.8 in 2003; a large amount of salt (e.g., Ca, Mg) in wastewater was adsorbed by the soil; the soil Al content (either exchangeable or oxalate extractable) decreased, while the oxalate-extractable Fe content remained at the same level. Ca-bound P accounted for > or = 70% of the total P adsorbed in the soil. The soil P adsorption capacity increased and was positively correlated with the concentration of exchangeable Ca in the soil. A higher concentration of exchangeable Ca was found in the 15-cm topsoil, where a higher total organic carbon was present. More P was accumulated in the upper soil than in the deeper soil. The adsorption of Ca in wastewater by the soil may extend the life expectancy of the Muskegon land treatment system.