Large scale toppling failure in metamorphic rock slopes

Imperial Users onl

Coagulant recovery from water treatment residuals: a review of applicable technologies

Conventional water treatment consumes large quantities of coagulant and produces even greater volumes of sludge. Coagulant recovery (CR) presents an opportunity to reduce both the sludge quantities and the costs they incur, by regenerating and purifying coagulant before reuse. Recovery and purification must satisfy stringent potable regulations for harmful contaminants, while remaining competitive with commercial coagulants. These challenges have restricted uptake and lead research towards lower-gain, lower-risk alternatives. This review documents the context in which CR must be considered, before comparing the relative efficacies and bottlenecks of potential technologies, expediting identification of the major knowledge gaps and future research requirements

Cybersecurity is the defining business challenge of the 21st century

The digital era brings opportunities, but also the obligation to protect firm and customers from its pitfalls, writes James Jarvi

The 5E Swipe Emancipation from Welfare Dependency

Abstract Community leadership is vital in efforts that enable intergeneration freedom from welfare dependence. This dissertation contains the efforts of a community leader on the path to influence, impact and emancipate generations of inner-city families from welfare dependency. This dissertation evaluated the effectiveness of an intervention named 5E Swipe for Success created to aid able bodied recipients from the dependency on welfare to self- sufficiency. The 5E Swipe for Success(5ESFS) that was program helped seven participants become emancipated from the systemic oppression of welfare dependency. This outcome occurred through the development of a program that extended learning opportunities—and its effectiveness tested through program activities. Methods used in this study included a program survey that was completed by 130 participants. Initially a total of 130 participants were evaluated using the survey as a benchmark for entering the program. Only fifteen participants went through the 5ESFS training successfully. These 15 trained participants were then given another survey, the Training Assessment Survey(TAS) at the beginning and end of the training. The TAS highligted the five modules of the training. . The TAS was taken for the second time to test the improvement level of the trainees. Out of the 15 participants, eight did not finish the training and only seven finished. Finally, five of the 15 participants were chosen for another sample survey as a result of displaying the ideal outcomes of the training. The researcher observed the participants, but reported only relevant observations from their experience in training

Acidified and ultrafiltered recovered coagulants from water treatment works sludge for removal of phosphorus from wastewater

This study used a range of treated water treatment works sludge options for the removal of phosphorus (P) from primary wastewater. These options included the application of ultrafiltration for recovery of the coagulant from the sludge. The treatment performance and whole life cost (WLC) of the various recovered coagulant (RC) configurations have been considered in relation to fresh ferric sulphate (FFS). Pre-treatment of the sludge with acid followed by removal of organic and particulate contaminants using a 2kD ultrafiltration membrane resulted in a reusable coagulant that closely matched the performance FFS. Unacidified RC showed 53% of the phosphorus removal efficiency of FFS, at a dose of 20 mg/L as Fe and a contact time of 90 min. A longer contact time of 8 h improved performance to 85% of FFS. P removal at the shorter contact time improved to 88% relative to FFS by pre-acidifying the sludge to pH 2, using an acid molar ratio of 5.2:1 mol H+:Fe. Analysis of the removal of P showed that rapid phosphate precipitation accounted for >65% of removal with FFS. However, for the acidified RC a slower adsorption mechanism dominated; this was accelerated at a lower pH. A cost-benefit analysis showed that relative to dosing FFS and disposing waterworks sludge to land, the 20 year WLC was halved by transporting acidified or unacidified sludge up to 80 km for reuse in wastewater treatment. A maximum inter-site distance was determined to be 240 km above the current disposal route at current prices. Further savings could be made if longer contact times were available to allow greater P removal with unacidified RC

Coagulant recovery and reuse for drinking water treatment

Coagulant recovery and reuse from waterworks sludge has the potential to significantly reduce waste disposal and chemicals usage for water treatment. Drinking water regulations demand purification of recovered coagulant before they can be safely reused, due to the risk of disinfection by-product precursors being recovered from waterworks sludge alongside coagulant metals. While several full-scale separation technologies have proven effective for coagulant purification, none have matched virgin coagulant treatment performance. This study examines the individual and successive separation performance of several novel and existing ferric coagulant recovery purification technologies to attain virgin coagulant purity levels. The new suggested approach of alkali extraction of dissolved organic compounds (DOC) from waterworks sludge prior to acidic solubilisation of ferric coagulants provided the same 14:1 selectivity ratio (874 mg/L Fe vs. 61 mg/L DOC) to the more established size separation using ultrafiltration (1285 mg/L Fe vs. 91 mg/L DOC). Cation exchange Donnan membranes were also examined: while highly selective (2555 mg/L Fe vs. 29 mg/L DOC, 88:1 selectivity), the low pH of the recovered ferric solution impaired subsequent treatment performance. The application of powdered activated carbon (PAC) to ultrafiltration or alkali pre-treated sludge, dosed at 80 mg/mg DOC, reduced recovered ferric DOC contamination to <1 mg/L but in practice, this option would incur significant costs. The treatment performance of the purified recovered coagulants was compared to that of virgin reagent with reference to key water quality parameters. Several PAC-polished recovered coagulants provided the same or improved DOC and turbidity removal as virgin coagulant, as well as demonstrating the potential to reduce disinfection byproducts and regulated metals to levels comparable to that attained from virgin material

Reuse of recovered coagulants in water treatment: An investigation on the effect coagulant purity has on treatment performance

Coagulant recovery offers many potential benefits to water treatment, by reducing chemical demand and waste production. The key obstacle to successful implementation is achieving the same levels of treatment quality and process economics as commercial coagulants. This study has evaluated the selectivity of pressure-filtration in the role of a low-cost coagulant recovery technology from waterworks sludge. The treatment performance of the purified recovered coagulant was directly compared to fresh and raw recovered coagulants. DOC and turbidity removal by recovered coagulants was close to that of commercial coagulants, indicating that coagulant can be successfully recovered and regenerated by acidifying waterworks sludge. However, performance was less consistent, with a much narrower optimum charge neutralisation window and 10–30% worse removal performance under optimum conditions. This inferior performance was particularly evident for recovered ferric coagulants. The impact of this was confirmed by measuring THM formation potential and residual metals concentrations, showing 30–300% higher THMFPs when recovered coagulants were used. This study confirms that pressure-filtration can be operated on an economically viable basis, in terms of mass flux and fouling. However, the selectivity currently falls short of the purity required for potable treatment, due to incomplete rejection of sludge contaminants

Occupational allergy to low molecular weight organic chemicals: the role of structure in determining chemical hazard

A number of low molecular weight (LMW) organic chemicals are known to cause occupational respiratory or skin sensitisation. A set of 200 LMW organic skin and approximately 75 respiratory sensitisers were identified by critical appraisal of published case literature. The respiratory sensitisers (asthmagens) were systematically compared in turn with suitable control chemicals and the skin sensitisers using a case-control methodology. The control chemicals were selected from known hazardous LMW organic chemicals for which no reports of respiratory sensitisation could be found.Several potential methods of differentiating between asthmagens and controls or asthmagens and skin sensitisers (by chemical structure alone) were investigated. These comprised hazardous fragment identification by calculating odds ratios for hazard (HOR's), cluster analysis and the logistic regression analysis. Of these methods the most effective approach was the logistic regression analysis. Using these methods several known or suspected hazardous substructures were confirmed to present statistically significant occupational asthma (OA) hazard. These included isocyanates, acid anhydrides, acrylates and (oligo)-amines. Furthermore, certain sub-structural fragments such as chlorine atoms appeared to provide a protective effect from OA hazard. For differentiating between skin sensitisers and asthmagens it was noted that fragments with carbon double bonded to nitrogen or oxygen atoms were significantly more prevalent in the respiratory sensitisers set.A predictive model of chemical asthma hazard was created using logistic regression and the model tested on a validation set of chemicals yielded a predictive kappa value greater than 0.7. This model is available for predictive testing of compounds for asthma hazard via the World Wide Web.This work demonstrates that simple structural information may, in conjunction with a well designed methodology, be used to identify occupational sensitisers with reasonable reliability

Mining association rules for admission control and service differentiation in e-commerce applications

Workload demands in e-commerce applications are very dynamic in nature, therefore it is essential for internet service providers to manage server resources effectively to maximise total revenue in server overloading situations. In this paper, a data mining technique is applied to a typical e-commerce application model for identification of composite association rules that capture user navigation patterns. Two algorithms are then developed based on the derived rules for admission control, service differentiation and priority scheduling. Our approach takes the following into consideration: a) only final purchase requests result in company revenue; b) any other request can potentially lead to a final purchase, depending upon the likelihood of the navigation sequence that starts from current request and leads to final purchase; c) service differentiation and priority assignment are based on aggregated confidence and average support of the composite association rules. As identification of composite association rules and computation of confidence and support of the rules can be pre-computed offline, the proposed approach incurs minimum performance overheads. The evaluation results suggest that the proposed approach is effective in terms of request management for revenue maximisation