A continuous active monitoring approach to identify cross-connections between potable water and effluent distribution systems.

A continuous active monitoring approach was developed for identification of cross-connections between potable water supply systems and treated wastewater effluent reuse distribution systems. The approach is based on monitoring the oxidation reduction potential (ORP) at the potable water system while injecting sulfite (a reducing agent) into the effluent line. A sharp decrease in the ORP of the potable water would indicate a cross-connection event. The approach was tested in batch experiments on treated municipal wastewater effluent of varying degree of treatment, and at dilution ratios of up to 1:100 (effluent/potable). The approach was then examined under continuous flow conditions, which simulated cross-connection events at various dilution ratios (up to 1:100). In the continuous runs, differences between the potable water ORP and the effluent-potable water mixture (containing sulfite as sodium bisulfite (SBS)) ORP were 450-630 mV. This suggests high potential for identifying a cross-connection event. Implementation of the approach includes adding sulfite to effluent used for agricultural irrigation; hence, possible effects on soil and on crops were studied in soil columns and pots planted with basil (Ocimum basilicum) as a model plant. No negative effects of sulfite addition to the irrigation effluent were observed in the irrigated soils and plants, and therefore, it could be safely implemented also in agricultural applications.

Assessment of the effects of greywater reuse on gross solids movement in sewer systems.

Onsite greywater reuse (GWR) and installation of water-efficient toilets (WETs) reduce urban freshwater demand and thus enhance urban water use sustainability. Research on GWR and WETs has generally overlooked their potential effects on municipal sewer systems: GWR and WETs affect the flow regime in sewers, and consequently also influence gross solids transport. To asses these impacts, a gross solids transport model was developed. The model is based on approaches found in the literature. Hydrodynamic calculations of sewage flow were performed using the SIMBA6 simulator and then used for the gross solid movement models. Flow characteristics in the up- and downstream sections of the sewer network differ. Therefore different approaches were used to model solids movement in each of these two parts. Each model determines whether a solid moves as a result of a momentary sewage flow, and if it moves, calculation of its velocity is possible. The paper shows the adoption and implementation of two gross solids transport models using SIMBA6 and depicts the results of the effects of various GWR and WET scenarios on gross solids movement in sewers for a real case study in Israel.

Reliability of on-site greywater treatment systems in Mediterranean and arid environments - a case study.

On-site greywater (GW) treatment and reuse is gaining popularity. However, a main point of concern is that inadequate treatment of such water may lead to negative environmental and health effects. Maintenance of single-family home GW systems is usually performed by home owners with limited professional support. Therefore, unless GW systems are reliable, environmental and public health might be compromised. This study is aimed at investigating the reliability of on-site recirculated vertical flow constructed wetlands (RVFCW) in 20 single-family homes. In order to ensure reliability, the failure-tree approach was adopted during the design and construction of the systems. The performance of the systems was monitored for 1.5 years, by evaluating treated GW flow and quality, and by recording all malfunctions and maintenance work. Only 39 failures occurred during this period, of which four caused irrigation with impaired quality GW, while the rest led to no irrigation. The mean time between failures (MTBF) was 305 days; two out of the 20 systems suffered from seven malfunctions (each), while nine systems did not fail at all. Thus, it can be postulated that if on-site GW treatment systems are designed with the right controls, and if scheduled (basic and relatively infrequent) maintenance is performed, GW reuse can be safe to the environment and human health.

Modelling the effects of on-site greywater reuse and low flush toilets on municipal sewer systems.

On-site greywater reuse (GWR) and installation of water-efficient toilets (WET) reduce urban freshwater demand. Research on GWR and WET has generally overlooked the effects that GWR may have on municipal sewer systems. This paper discusses and quantifies these effects. The effects of GWR and WET, positive and negative, were studied by modelling a representative urban sewer system. GWR scenarios were modelled and analysed using the SIMBA simulation system. The results show that, as expected, the flow, velocity and proportional depth decrease as GWR increases. Nevertheless, the reduction is not evenly distributed throughout the day but mainly occurs during the morning and evening peaks. Examination of the effects of reduced toilet flush volumes revealed that in some of the GWR scenarios flows, velocities and proportional depths in the sewer were reduced, while in other GWR scenarios discharge volumes, velocities and proportional depths did not change. Further, it is indicated that as a result of GWR and installation of WET, sewer blockage rates are not expected to increase significantly. The results support the option to construct new sewer systems with smaller pipe diameters. The analysis shows that as the penetration of GWR systems increase, and with the installation of WET, concentrations of pollutants also increase. In GWR scenarios (when toilet flush volume is not reduced) the increase in pollutant concentrations is lower than the proportional reduction of sewage flow. Moreover, the results show that the spatial distribution of houses reusing GW does not significantly affect the parameters examined.

Potential impacts of on-site greywater reuse in landscape irrigation.

This study investigated the effects of irrigation with different types of waters on soil, plants, and public health. The test plant was ryegrass grown in 12 planters filled with sandy loam soil and irrigated with three types of waters (4 planters for each type): freshwater, raw domestic light greywater (GW), and treated domestic light GW. The sodium adsorption ratio (SAR), EC, pH and alkalinity of the three types of irrigation waters did not differ significantly, suggesting that raw or treated light GW should not exhibit negative effects. Concentrations of anionic and cationic surfactants in the freshwater and the treated GW were about the same, while their concentrations in the raw GW were higher. Surfactant levels in the three drainage water types were low. Some accumulation of surfactants occurred in planters irrigated with raw and treated GW. The COD of the drainage water of planters irrigated with raw GW was higher than the COD of other two drainage water types. Although raw and treated GW contained faecal coliforms, they were hardly detected in the drainage waters. All plants did not show any signs of stress. This may be due to the fact that the GW originated mainly from showers and washbasins.

Modeling highway runoff pollutant levels using a data driven model.

Pollutants accumulated on road pavement during dry periods are washed off the surface with runoff water during rainfall events, presenting a potentially hazardous non-point source of pollution. Estimation of pollutant loads in these runoff waters is required for developing mitigation and management strategies, yet the numerous factors involved and their complex interconnected influences make straightforward assessment almost impossible. Data driven models (DDMs) have lately been used in water and environmental research and have shown very good prediction ability. The proposed methodology of a coupled MT-GA model provides an effective, accurate and easily calibrated predictive model for EMC of highway runoff pollutants. The models were trained and verified using a comprehensive data set of runoff events monitored in various highways in California, USA. EMCs of Cr, Pb, Zn, TOC and TSS were modeled, using different combinations of explanatory variables. The models' prediction ability in terms of correlation between predicted and actual values of both training and verification data was mostly higher than previously reported values. Pb(Total) was modeled with an outcome of R2 of 0.95 on training data and 0.43 on verification data. The developed model for TOC achieved R2 values of 0.91 and 0.49 on training and verification data respectively.

Assessment of the reliability of an on-site MBR system for greywater treatment and the associated aesthetic and health risks.

This study analyses the reliability of an on-site MBR system for greywater treatment and reuse. To achieve this goal simulation was performed based on the IWA ASM1 model which was adapted to describe biological and physical mechanisms for MBR greywater treatment based systems. Model results were found to agree well with experimental data from an on site pilot greywater treatment plant, after which the calibrated model was used in a Monte Carlo mode for generating statistical data on the MBR system performance under different scenarios of failures and inflow loads variations. Effluents quality and their associated risks were successfully estimated.

Centralised urban wastewater reuse: what is the public attitude?

Public support is crucial for successful implementation of wastewater reuse projects. This paper analyses the findings of a questionnaire-type survey (256 participants) conducted to determine the attitude of Israeli urban public towards possible urban reuse options. The paper summarises the support/objection to 13 reuse options and the correlation between support and environmental awareness and perceptions. Results show that a high proportion of the participants supported options perceived as low-contact, such as irrigation of public parks (96%), sidewalk landscaping (95%) and use in the construction industry (94%), while higher-contact reuse options found less support (e.g. commercial launderettes, 60%). No correlation was found between biographical characteristics and support (education, gender, income, age). Based on the results, public campaigns in Israel should focus on disseminating information regarding wastewater treatment technologies, discuss health related issues, highlight the positive economic impact of water reuse and generate a positive public opinion, as these factors tend to influence individuals to support reuse projects.

Comparative study of the microbial quality of greywater treated by three on-site treatment systems.

This paper analyses the performance of a pilot scale treatment plant, treating light domestic greywater. The treatment included three parallel treatment units: stand-alone sand filtration (SFEB), RBC followed by sand filtration (SFRBC), and an MBR equipped with UF membranes (MBR). The performance of the SFEB unit was rather poor. The RBC and MBR units produced effluent of excellent quality, with COD of 42 and 40 mg l(-1), BOD of 1.8 and 1.1 mg l(-1), and turbidity of 0.6 and 0.2 NTU respectively. The SFEB failed to remove heterotrophic microorganisms (HPC), while the SFRBC and the MBR exhibited 2.1 and 3.6 logs removal, leading to effluent concentrations of 1.1 x 10(3) and 8.8 x 10(3) cfu ml(-1) respectively. Faecal coliforms (FC) counts were 3.4 x 10(5) 1.4 x 10(5) 1.1 x 10(3) and 3.5 x 10(2) cfu 100 ml(-1) in raw greywater, and in the SFEB, SFRBC and MBR effluents respectively. Further, in 60% of the samples no FC were detected in the MBR effluent. In order to simulate residence times in full scale systems, effluents were disinfected and stored for 0.5 h, 3 h, 6 h (normal operation), and one week (extreme event). The average chlorine demand was 8.1, 3.8 and 2.9 mg l(-1) for SFEB, SFRBC and MBR effluents respectively. Low residual chlorine (0.15-0.22 mg l(-1)) remained in all effluents even after a week-long storage. Disinfection reduced HPC by 5, 2 and 2 orders of magnitude in the SFEB, SFRBC and MBR effluents respectively, with no regrowth in short contact times (up to 6 hours). Some regrowth was observed after a week-long storage leading to 10(6), 10(4) and 10(3) cfu ml(-1) (SFEB SFRBC and MBR respectively). Disinfection reduced FC counts in all three types of effluent to 0 cfu 100 ml(-1), whilst no FC regrowth was observed after week-long storage. The results show that both RBC and MBR treatment units are viable options for on-site greywater reuse. The disinfection experiments strongly indicate that the health risk associated with the reuse of these effluents is minimal even after long period of storage.

On-site greywater treatment and reuse in multi-storey buildings.

The paper presents a study of a pilot plant treating light greywater for seven flats. The pilot plant combines biological treatment (RBC) with physicochemical treatment (sand filtration and disinfection). The pilot plant produced effluent of excellent quality, meeting the urban reuse quality regulations, and was very efficient in TSS turbidity and BOD removal: 82%, 98% and 96%, respectively. COD removal was somewhat lower (70-75%) indicating that the greywater may contain slowly-biodegradable organics. The RBC (attached growth biological system) was able to retain most of the solids as a result of bioflocculation; further it was proven to have very stable and reliable performance. Faecal coliforms and heterotrophic reductions were very high (100% and 99.99%, respectively) producing effluent that also met drinking water standards. The combination of low organic matter, nutrients and microbial indicators reduces the regrowth and fouling potentials in the reuse system, thus ensuring safe reuse of the treated greywater for toilet flushing.

Quality of individual domestic greywater streams and its implication for on-site treatment and reuse possibilities.

A sampling campaign was conducted in order to characterise the quality and quantity of individual domestic greywater streams. Based on the results, various scenarios of inclusion and / or exclusion of different greywater streams were explored, and their implication for on-site greywater treatment and reuse options are discussed. Domestic greywater was found to contribute as much as 55-70% of the specific daily load of TSS and BOD, in municipal sewage. The kitchen sink was signalled out as a major contributor of VSS, CODt, and BODt with 58%, 42% and 48%, of their total daily load respectively. The washing machine was established as a significant contributor of sodium, phosphate and CODt (40%, 37% and 22% of the total load). The dishwasher, although contributing only 5% of the flow, was found to be a significant contributor of phosphate and boron. The wash basin was found to be the least polluting appliance. As "demand" for greywater within the urban environment is lower than its "production", it is logical to recycle only the less polluted greywater streams. In order to explore the consequences of the above concept on discharge volume, pollutants loads and concentrations, 18 scenarios were studied, in each at least one stream was excluded from the combined greywater stream. Exclusion of the joined stream of the kitchen sink plus the highly polluted streams of the washing machine (wash + 1st rinse) and dishwasher (pre-rinse + wash) significantly improved greywater quality, with the advantage of leaving enough greywater to be reused (65-70 l/c/d).

Comparative effects of two beta-blockers on cardiovascular reactivity and type A behavior in hypertensives.

This study compared the effects of beta-blockers differing in degree of central nervous system penetration on Type A behavior and cardiovascular reactivity to mental stress. Forty-six male hypertensives were assigned randomly to receive either highly lipophilic and nonselective propranolol, hydrophilic and cardioselective atenolol, the diuretic hydrochlorothiazide, or placebo. Subjects were administered parallel forms of the Structured Interview (SI) and performed mental arithmetic and a cognitive task prior to and after 6 weeks of therapy. Results indicated that diuretic and placebo subjects (subsequently combined into a single control group) did not differ and that both beta-blockers reduced heart rate but not blood pressure reactivity to mental stress (p less than 0.02), an effect that was strongest during the mental arithmetic test. Analysis of SI components indicated a reduction only in explosive speech for beta-blockers versus controls (p less than 0.05). For global SI classifications, seven out of 12 subjects (58%) receiving propranolol, three of 12 (25%) receiving atenolol, and four of 22 control subjects (18%) became less Type A (p less than 0.05). These data do not replicate results of a prior study obtained with atenolol and suggest that only a subset of hypertensive individuals show reduced Type A behavior with propranolol. Central nervous system mechanisms may be important in producing these effects.

Fluoride prescribing patterns among primary care physicians.

Fluoride supplement prescribing habits of US Air Force primary care physicians were studied. A questionnaire was sent to all active duty Air Force obstetricians, family physicians, and pediatricians assigned within the continental United States. Few obstetricians and family physicians in the Air Force currently prescribe prenatal fluoride supplements. The majority of respondents are skeptical of its efficacy or state that local water contains adequate amounts. Only 2.5 percent of all physicians question prenatal fluoride's safety. Fluoride supplements for breast-feeding infants are correctly prescribed by 80 percent of pediatricians and 54 percent of family physicians (P = .0002). Pediatricians more often know the local concentration of fluoridated water and more readily prescribe fluoride for children of all ages. Primary care physicians, especially family physicians, are in an excellent position to practice caries prevention. The survey results indicate a need for more physician education on the current issues and proper use of fluoride supplements.

Eosinophilic fasciitis: an underdiagnosed syndrome.

Eosinophilic fasciitis is characterized by peripheral eosinophilia, diffuse induration of the skin (particularly of the extremities), thickened fascia, and responsiveness to corticosteroids. Since it was first described in 1974, 36 cases have been reported. We have presented three new cases diagnosed in our community hospital during the last 27 months, with reports on their follow-up while being treated with corticosteroids. We believe the disorder to be more common than reports indicate.

Serum lymphocytotoxins in inflammatory bowel disease. Studies of frequency and specificity for lymphocyte subpopulations.

Serum cold-reactive lymphocytotoxin (LCT) was detected in twenty-two of fifty-six (40%) patients with inflammatory bowel disease (IBD). The frequency of LCT detection was similar in Crohn's disease and ulcerative colitis. Cytotoxicity testing against T or B cell-enriched peripheral blood lymphocytes from normal donors, together with absorption experiments, indicated that LCT in IBD was reactive against determinants on both cell subpopulations. Reactivity against T cells from patients with common variable immunodeficiency was significantly less than with normal donor T cells. LCT in IBD could not be related to prior allogeneic sensitization and its presence appeared to be unrelated to disease activity or drug therapy. No correlation was found between LCT and peripheral blood T- or B-cell numbers. The present findings suggest the need for further investigation of the role of infectious agents in the pathogenesis of IBD.