Fouling of a spiral-wound reverse osmosis membrane processing swine wastewater: effect of cleaning procedure on fouling resistance.

Swine manure is a valuable source of nitrogen, phosphorus and potassium. After solid-liquid separation, the resulting swine wastewater can be concentrated by reverse osmosis (RO) to produce a nitrogen-potassium rich fertilizer. However, swine wastewater has a high fouling potential and an efficient cleaning strategy is required. In this study, a semi-commercial farm scale RO spiral-wound membrane unit was fouled while processing larger volumes of swine wastewater during realistic cyclic operations over a 9-week period. Membrane cleaning was performed daily. Three different cleaning solutions, containing SDS, SDS+EDTA and NaOH were compared. About 99% of the fouling resistance could be removed by rinsing the membrane with water. Flux recoveries (FRs) above 98% were achieved for all the three cleaning solutions after cleaning. No significant differences in FR were found between the cleaning solutions. The NaOH solution thus is a good economical option for cleaning RO spiral-wound membranes fouled with swine wastewater. Soaking the membrane for 3 days in permeate water at the end of each week further improved the FR. Furthermore, a fouling resistance model for predicting the fouling rate, permeate flux decay and cleaning cycle periods based on processing time and swine wastewater conductivity was developed.

Membrane filtration of the liquid fraction from a solid-liquid separator for swine manure using a cationic polymer as flocculating agent.

The liquid fraction from a solid-liquid separator for swine manure, which used a cationic polymer to promote particle flocculation, was processed by one nanofiltration and two reverse osmosis spiral-wound membranes. Eight different liquid fraction batches (750 to 1750 L) were concentrated at volumetric concentration ratios (VCRs, initial to final volumes) ranging from 2.3 to 4.2. Membrane fouling intensity was highly variable, as water flux recovery after concentration cycles ranged from 13% to 88%. The most severe fouling was caused by a liquid fraction that had relatively low suspended solids (SS) (774 mg/L) and was concentrated at a low VCR of 2.6. Raw manure collected the same day also contained low SS, suggesting that fewer sites were available for polymer adsorption and thus more polymer remained in the liquid. However, because of the high opacity of the samples, residual polymer could not be detected in any feed or concentrate samples. Fouling was not totally irreversible as over 97% of membrane flux could be recovered by cleaning with acidic and alkaline solutions. Further tests with spiked liquid fractions indicated that fouling due to residual polymer in solution started to occur at a polymer concentration of 3 and 11 mg/L in initial and concentrated effluents, respectively. If a cationic polymer is used to pretreat manure, the amount of added polymer would have to be closely related to SS content as opposed to manure volume, in order to leave very little residual polymer in solution.

Nitrogen potential recovery and concentration of ammonia from swine manure using electrodialysis coupled with air stripping.

The practice of intensive animal production in certain areas has resulted in excessive manure production for the available regional land base. Consequently, there is a need to develop treatment technologies to recover the valuable nutrients that manure contains so that the resulting product can be transported and used as fertilizer on agricultural land. The project presented here used electrodialysis in a dilution/concentration configuration to transfer the manure ammonia in the diluate solution by electromigration to an adjacent solution separated by an ion-exchange membrane under the driving force of an electrical potential. Then, air stripping from the electrodialysis-obtained concentrate solution without pH modification was used to isolate the ammonia in an acidic solution. An optimal process operating voltage of 17.5 V was first determined on the basis of current efficiency and total energy consumption. During the process, the swine manure pH varied from 8.5 to 8.2, values favourable for NH(4)(+) electromigration. Total ammonia nitrogen reached 21,352 mg/L in the concentrate solution, representing approximately seven times the concentration in the swine manure. Further increases in concentration were limited by water transfer from the diluate solution due to electroosmosis and osmosis. Applying vacuum to the concentrate reservoir was found to be more efficient than direct concentrate solution aeration for NH(3) recuperation in the acid trap, given that the ammonia recuperated under vacuum represented 14.5% of the theoretical value of the NH(3) present in the concentrate solution as compared to 6.2% for aeration. However, an excessively low concentrate solution pH (8.6-8.3) limited NH(3)volatilization toward the acid trap. These results suggest that the concentrate solution pH needs to be raised to promote the volatile NH(3) form of total ammonia nitrogen.

Fouling characterization of electrodialysis membranes used for the recovery and concentration of ammonia from swine manure.

The aim of the present study was to: (1) identify the nature of fouling for ED membranes (AMX and CMB, from Tokuyama Soda, Japan) used for the isolation and concentration of total NH(3)-N from swine manure, (2) determine the effect of fouling on membrane integrity, (3) establish the relation between fouling type and manure composition, and (4) estimate the efficiency of a two-step cleaning procedure to restore membranes properties. After processing 10 batches of swine manure (or 240 L/m(2)), the average current density as well as the membranes electrical conductivity and ion-exchange capacity decreased. The decline in process performance was associated with membrane fouling, since a significant deposit, possibly calcium carbonate and silica colloidal particles, was observed on the fouled AMX membranes. The electrical conductivity and ion-exchange capacity of the CMB membrane was completely restored by a two-step cleaning procedure using 0.5% NaOH and 1% HCl. However, for the electrical conductivity of the AMX membranes it was only partially recovered. The on-line cleaning procedure efficiency was assessed by measuring the stack average current density and the decrease of manure conductivity during 1h tests. Values for the cleaned membranes were, respectively, 95% and 91% the ones measured with the new membranes, and were significantly higher than for the fouled membranes.

Use of electrodialysis and reverse osmosis for the recovery and concentration of ammonia from swine manure.

This project aimed at producing a concentrated nitrogen fertilizer from liquid swine manure using electrodialysis (ED) and reverse osmosis (RO), as a mean to help resolve the excess nutrient problem faced by many swine producers, and offer an alternative to chemical nitrogen fertilizer production. Different types of ED membranes were evaluated based on the NH4+ transfer rate, current efficiency and membrane stability. A combination of CMB/AMX membranes was retained due to its high NH4+ transfer rate and chemical stability. The maximum total ammonia concentration (NH3-N) achievable by ED was limited by water transport from the manure to the concentrate compartment, and ammonia volatilization (17%) from the open concentrate compartment. Results suggested that, under the conditions of this experiment, a maximum total NH3-N concentration of about 16g/L could be reached with the ED system. An ED concentrate (8.7g/L of total NH3-N) was also fed to TFC-HF reverse osmosis membranes. A mass balance analysis revealed that the RO permeate, which represented 49.6% of the initial volume, contained 8.6% of the ammonia. However, the RO concentrate contained only 66.6% of the initial total NH3-N, suggesting that 21.2% of the ammonia was volatilized during the concentration test with RO membranes. Ammonia concentration in the RO concentrate reached approximately 13g/L, which is similar to the maximum concentration that could be achieved by ED. These results suggest that the use of ED and RO membranes to recover and concentrate ammonia is potentially interesting but the process must include an approach to minimize ammonia volatilization or trap volatilized ammonia.

HIV infection among sex workers in Accra: need to target new recruits entering the trade.

OBJECTIVE: Description of the epidemiology of HIV infection among sex workers (SW) in Accra, Ghana. METHODS: In all, 1013 SW working out of their homes ( seaters ) or finding customers in bars, hotels, brothels or on the street ( roamers ) were interviewed and tested for HIV. RESULTS: Overall, prevalence of HIV infection was nearly 50% (506 of 1013), varying from 26% (133 of 507) among the roamers to 74% (368 of 496) among the seaters. Profound differences were noted between these two categories of SW with regard to age, number of clients per day, price per instance of intercourse, condom use, and other characteristics. Respectively, 27% and 58% of roamers and seaters were infected with HIV within their first 6 months of sex work, despite a limited number of unprotected sex acts with seropositive clients. Independent risk factors for HIV infection varied between types of SW: age among the roamers; region of origin and duration of sex work among the seaters; number of clients per day, and presence of current or past genital ulcer and gonococcal cervicitis in both groups. CONCLUSION: In Accra, considerable heterogeneity exists in the population of SWs. In both categories of SW, new recruits become rapidly infected with HIV after entering the trade. The 25-fold higher prevalence of HIV among SWs than in the general adult population suggests that in Accra, as in many cities of West Africa, a high fraction of new cases of HIV infection continue to be acquired from SWs. Intervention programs targeting SW should be an essential component of national AIDS control strategies. Special efforts should be made to identify and offer preventive services to new sex workers.

Defense of breast cancer malpractice claims.

The goal of this study was to determine whether factors associated with the successful defense and cost of malpractice cases involving the failure to diagnose breast cancer could be identified in medical and legal records. Secondary goals were to develop a multidisciplinary clinical algorithm utilizing National Comprehensive Cancer Network (NCCN) practice guidelines with practitioner risk management strategies. Physician deviations from these guidelines were tracked to identify high-risk areas in the diagnosis of breast cancer. A multidisciplinary clinical algorithm was introduced and practitioner risk management issues were addressed. In this study specific medical, legal, and cost factors were retrospectively abstracted and analyzed to identify associations between medical and legal factors and medicolegal outcome. ProMutual handled 156 malpractice cases involving breast cancer between January 22, 1986, and November 20, 1997. Of the total, 124 cases involving 212 defendants were closed. The closed cases were analyzed, using multivariable stepwise logistic and linear regression, to identify associations between clinical factors and case outcome. Women's health practitioners (WHPs), including obstetrician-gynecologists (OB-GYNs), family medicine, and internal medicine clinicians, were the largest group of defendants (97). Others included radiologists (43), surgeons (33), and pathologists (3). OB-GYNs accounted for 31% of these defendants, with a cost of more than $16 million. The greatest number of specialists represented in the open cases were radiologists, with 38% of the total. The defense model predicts that the probability of successful defense is lessened with inadequate record keeping, a patient that has metastasis and is alive, and a delay in diagnosis of 12 months or more. The overall indemnity model predicts a higher indemnity with the spread of disease at the time of evaluation, a patient who has metastasis and is alive, and a date of occurrence closer to the present. Indemnity is less in patients who have had a lymph node dissection, who have died, or who are alive without metastasis. The WHP model predicts an increased overall indemnity with the spread of disease at the time of evaluation and the presence of a mass without pain. Indemnity decreases with a history of pregnancy, absence of presenting symptoms, or presentation with pain with or without a mass, and the performance of a lymph node dissection.

Stressful life events and survival after breast cancer.

OBJECTIVE: This study assessed the relation of stressful life events with survival after breast cancer. METHODS: This study was based on women with histologically confirmed, newly diagnosed, localized or regional stage breast cancer first treated in 1 of 11 Quebec City (Canada) hospitals from 1982 through 1984. Among 765 eligible patients, 673 (88%) were interviewed 3 to 6 months after diagnosis about the number and perceived impact of stressful events in the 5 years before diagnosis. Three scores were calculated: number of events; number weighted by reported impact; and for almost 80% of events, number weighted by community-derived values reflecting adjustment required by the event. Scores were divided into quartiles to assess possible dose-response relationships. Survival was assessed in 1993. Hazard ratios and 95% confidence intervals (CIs) comparing all-cause and breast cancer-specific mortality were calculated with adjustment for age, presence of invaded axillary nodes, adjuvant radiotherapy, and systemic therapy (ie, chemotherapy and hormone therapy). RESULTS: When quartiles 2, 3, and 4 were compared with the appropriate lowest quartile, adjusted hazard ratios for all-cause mortality were 0.99 (CI = 0.70-1.38), 0.97 (CI = 0.73-1.31), and 1.04 (CI = 0.78-1.40) for number, number weighted by impact, and number weighted by community-derived values, respectively. Results were essentially similar for the relation between stressful life events limited to those occurring within the 12 months before diagnosis and overall mortality and between stressful life events in the 5 years before diagnosis and breast cancer-specific mortality. CONCLUSIONS: Stress was conceptualized as life events presumed to be negative, undesirable, or to require adjustment by the person confronting them. We found no evidence indicating that this kind of stress during the 5 years before diagnosis negatively affected survival among women with nonmetastatic breast cancer. Evidence from this study and others on the lack of effect of this type of stress on survival may be reassuring for women living with breast cancer.

Knowledge on periconceptional use of folic acid in women of British Columbia.

OBJECTIVE: Our purpose was to evaluate the knowledge of folic acid and its use preconceptionally in women of British Columbia. METHODS: The study was conducted at British Columbia Women's Hospital in Vancouver, Canada, between April 15 and June 15, 1999. Pregnant women and women in the postpartum period were asked to complete a survey on folic acid. RESULTS: In total, 1,004 women completed the questionnaire during the study period. Seventy-one percent of the women knew that vitamins could help prevent birth defects. Of those, 76.3% identified folic acid as the one vitamin specifically associated with reduction of birth defects. It was identified that 49.4% of all women took vitamins prior to pregnancy. CONCLUSIONS: Women in the population studied were relatively well informed about the benefits of folic acid, but less than 50% of them took vitamins prior to conception.

Job strain and sickness absence among nurses in the province of Québec.

BACKGROUND: Using Karasek's job strain model, the objective of the study was to determine whether nurses exposed to job strain had a higher incidence of sick leave than nurses not exposed. METHODS: The design was longitudinal. Data on sick leave were collected for 1,793 nurses for a 20-month period: short-term leaves and certified sick leaves. The Job Content Questionnaire was used to measure psychological demands, job decision latitude, and social support at work. RESULTS: Short-term sick leaves were associated with job strain (incidence density ratio (IDR) = 1.20) and with low social support at work (IDR = 1.26). Certified sick leaves were also significantly associated with low social support at work (IDR = 1.27 for all diagnoses and IDR = 1.78 for mental health diagnoses). CONCLUSIONS: Our results support the association between job strain and short-term sick leaves. The association with certified sick leaves is also significant for subgroups of nurses with specific job characteristics. Social support at work, although associated with all types of sick leaves measured, does not modify the association between job strain and absence.

When you suspect the healer needs healing.

By recognizing the causes of stress among physicians in your office or hospital and proactively addressing them, you can play a significant role in improving patient care.

Job strain and pregnancy-induced hypertension.

In a case-control study we assessed whether exposure to high job strain during the first 20 weeks of pregnancy increases the risk of preeclampsia and gestational hypertension. Cases (128 with preeclampsia and 201 with gestational hypertension) and controls (N = 401) were primiparous women who had a paid occupation for at least 1 week during the first 20 weeks of their pregnancy and who delivered between 1984 and 1986 in 10 hospitals of Quebec, Canada. Based on their job title, we assigned women scores of psychological demand and decision latitude derived from the National Population Health Survey and classified these women as exposed to high (high demand, low latitude) versus low (low demand, high latitude) job strain. Women exposed to high job strain were more likely to develop preeclampsia [adjusted odds ratio (aOR) = 2.1; 95% confidence interval (CI) = 1.1-4.1] than women exposed to low job strain. The risk was quite similar for women exposed to a full-time, high strain job (> or =35 hours per week) (aOR = 2.0) than in a part-time, high strain job (aOR = 1.8). High job strain increased the risk of gestational hypertension slightly (aOR = 1.3; 95% CI = 0.8-2.2). These results indicate that women exposed to high job strain are at higher risk of developing preeclampsia and, to a lesser extent, gestational hypertension.

Statistical models of outcome in malpractice lawsuits involving death or neurologically impaired infants.

The objective was to determine whether factors could be identified in medical and legal records that are associated with the successful defense of obstetrical malpractice cases involving the death or neurological impairment of infants. Obstetrical claims (169) closed by PROMUTUAL between January 1, 1990, and December 31, 1994, were retrospectively abstracted and analyzed to identify associations between medical and legal factors, and the medicolegal outcome. Multivariable analysis identifies that the use of pitocin, diagnosis of asphyxia, a delay in delivery, and the use of multiple defense expert witnesses decreased the chances of a successful defense. Two statistical models explaining indemnity payment were developed. The first, based on medical outcome, showed an increased indemnity payment when a case involved major neurological deficits, diagnosis of asphyxia, newborn seizures, later year of delivery, and participation of a particular defense firm. Perinatal or childhood death and the use of pitocin were indicators of a decrease in payment. The second model was based on long-term care requirements. In this model, indicators of increased indemnity payment were: nonreassuring intrapartum fetal heart rate tracing, later year of delivery, intensity of long-term care required, and participation of a particular defense law firm. Perinatal or childhood death, the use of pitocin, and settlement date increasingly removed from the occurrence date were the determinants of decreased payments in this model. Finally, the presence of major neurological deficits, the prolongation of a case, and the involvement of multiple law firms and defense witnesses increased the expense charged to and paid by the insurance company. Using the medical, legal, and financial data relevant to 169 obstetrical cases closed by one malpractice insurance carrier between 1990 and 1994, statistical models with potential predictive values for future malpractice claims involving neurologically impaired infants were constructed. These models may help determine in advance the chance a future case has for successful defense and the likely amount of expense and indemnity dollars that will be paid out to settle and defend it.

Family history of cognitive disabilities in first-degree relatives of autistic and mentally retarded children.

We compared with a family history method the rate of cognitive disabilities (CD) in 156 first-degree relatives of 49 autistic (AU) probands to that found in 55 first-degree relatives of 18 mentally retarded (MR) probands. Broadly defined CD were found in, respectively, 17 and 16% of the relatives of the AU and MR probands. However, the characteristics of the probands associated with a family history of CD are different in AU and MR: Female and low IQ AU probands have more first-degree relatives with CD. Our findings suggest that a positive family history of CD is not specific to autism when compared to mental retardation. The observation that female and low IQ probands have higher family history of CD may suggest heterogeneity within autistic children and provides leads for future family studies.

Markers of chemoresistance in ovarian carcinomas: an immunohistochemical study of 86 cases.

Markers of chemoresistance have been rarely investigated in human ovarian cancer. This study evaluates the clinical value in ovarian cancer of metallothionein (MT), heat-shock protein-27 (HSP-27) and glutathione-S-transferase pi and alpha (GST pi, GST alpha), recognized for their relation with drug resistance in vitro. The expression of these markers was evaluated by immunohistochemistry on paraffin-embedded tumor specimens from 86 patients with ovarian carcinomas diagnosed between 1977 and 1990 who received chemotherapy. Response to chemotherapy was evaluated using well-defined criteria. Marker expression was evaluated on a section of the primary tumor (81 cases) and, when available, on a section of tumor following chemotherapy (48 cases). MT was expressed in 38.3% of primary tumors unexposed to chemotherapy, HSP-27 in 50.6%, GST pi in 37%, and GST alpha in 50.6%. The expression of all four markers did not help to predict chemoresistance. The concordance between marker expression by the tumor before and after chemotherapy was weak (concordance, 51.2%-70.7%). Immunostaining was not associated (p > 0.1) with any prognostic factor such as stage, residual tumor after surgery and grade. Ovarian cancer is a highly heterogeneous neoplasm and the expression of markers of chemoresistance reflects this heterogeneity. Our data suggest that chemoresistance is more likely multifactorial and confirms the complexity of the in vivo model.

Randomised comparison of amoxycillin and erythromycin in treatment of genital chlamydial infection in pregnancy.

Erythromycin, the standard treatment for chlamydial infection in pregnant women, commonly causes side-effects, which limits its efficacy. In a randomised, double-blind study, we compared amoxycillin with erythromycin in this setting. 210 pregnant women with Chlamydia trachomatis infection were randomly assigned 7 days' treatment with amoxycillin (500 mg three times daily) or erythromycin (500 mg four times daily). Control cultures were obtained 21 days after treatment, during late pregnancy, and from the infant within a week of birth. Treatment was judged a failure if any post-treatment culture was positive or if the patient had to stop therapy because of severe side-effects. 11 women (5.2%) were lost to follow-up. 1 (of 100) amoxycillin-treated women had to stop treatment because of severe side-effects compared with 12 (of 99) erythromycin-treated women (p = 0.002). 1 woman in the amoxycillin group had a positive culture at the third-trimester examination. No positive post-treatment culture was found in the erythromycin group. Severe gastrointestinal side-effects were more common in women who received erythromycin (31 vs 6%, p < 0.001). The overall failure rate was therefore 2% in the amoxycillin group and 12% in the erythromycin group (p = 0.005). These results suggest that amoxycillin is an acceptable alternative to erythromycin for C trachomatis infection in pregnant women.

A statistical model for predicting the outcome in breast cancer malpractice lawsuits.

OBJECTIVE: To analyze specific medical, legal, and cost factors that predict the probability of successfully defending lawsuits filed because of failure to diagnose breast cancer. METHODS: Seventy-six malpractice cases handled by the Massachusetts Medical Professional Insurance Association between June 29, 1983 and December 30, 1993 were abstracted and analyzed using univariate analysis, multivariate stepwise logistic and least-square regression analysis, and the Cox proportional hazards model to identify statistically significant associations between clinical factors and medicolegal outcomes. RESULTS: Obstetrician-gynecologists were defendants in the largest number of cases (38) and incurred the highest total indemnity ($7,629,570). The probability of defending a suit successfully increased with smaller tumor size and younger patients (less than 40 years of age). The failure to perform a biopsy was associated with a decreased probability of successful defense. Variables predicting high case cost included younger patient age, an increased length of delay in diagnosis, and the failure to perform a biopsy. The presence of metastasis at diagnosis was associated with an increased interval from diagnosis to the initiation of a suit. CONCLUSION: Statistical models that use medicolegal and cost factors can predict both the probability of a successful defense and the total cost of a breast cancer malpractice case.