The impact of image-size manipulation and sugar content on children's cereal consumption.

Previous studies have demonstrated that portion sizes and food energy-density influence children's eating behavior. However, the potential effects of front-of-pack image-sizes of serving suggestions and sugar content have not been tested. Using a mixed experimental design among young children, this study examines the effects of image-size manipulation and sugar content on cereal and milk consumption. Children poured and consumed significantly more cereal and drank significantly more milk when exposed to a larger sized image of serving suggestion as compared to a smaller image-size. Sugar content showed no main effects. Nevertheless, cereal consumption only differed significantly between small and large image-sizes when sugar content was low. An advantage of this study was the mundane setting in which the data were collected: a school's dining room instead of an artificial lab. Future studies should include a control condition, with children eating by themselves to reflect an even more natural context.

A review of classic Fenton's peroxidation as an advanced oxidation technique.

Hydrogen peroxide (H(2)O(2)) is a strong oxidant and its application in the treatment of various inorganic and organic pollutants is well established. Still H(2)O(2) alone is not effective for high concentrations of certain refractory contaminants because of low rates of reaction at reasonable H(2)O(2) concentrations. Improvements can be achieved by using transition metal salts (e.g. iron salts) or ozone and UV-light can activate H(2)O(2) to form hydroxyl radicals, which are strong oxidants. Oxidation processes utilising activation of H(2)O(2) by iron salts, classically referred to as Fenton's reagent is known to be very effective in the destruction of many hazardous organic pollutants in water. The first part of our paper presents a literature review of the various Fenton reagent reactions which constitute the overall kinetic scheme with all possible side reactions. It also summarises previous publications on the relationships between the dominant parameters (e.g. [H(2)O(2)], [Fe(2+)], . . .). The second part of our review discusses the possibility of improving sludge dewaterability using Fenton's reagent.

A review of thermal sludge pre-treatment processes to improve dewaterability.

As a result of the wide application and utilization of the waste activated sludge process, excess sludge presents a serious disposal problem. Many efforts have been devoted to reduce the excess sludge by treatments such as digestion and dewatering. It has been known for many years that a thermal pre-treatment gives an improvement in the dewaterability of sludges. This paper provides a literature review concerning the optimum treatment conditions to obtain enhanced dewaterability and digestibility of sludge. The main commercial hydrolysis processes (Cambi, Porteous and Zimpro) are discussed. The literature findings concerning the optimum treatment conditions of thermal or thermochemical pre-treatments are reviewed. The second part of this paper deals with the fundamentals of improving sludge dewatering. The influence of extracellular polymer (ECP) on settling and dewatering characteristics is discussed, together with the importance of cations and ECP-hydrophobicity in the flocculation and dewatering process. Finally, the effect on exocellular polymer, dewaterability, settleability and colloidal stability of activated sludge by treatment with sulfuric acid was studied.

Pilot-scale peroxidation (H2O2) of sewage sludge.

Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess sludge is an inevitable drawback inherent to the waste activated sludge process. Both the reduction of the amount of sludge produced and improving its dewaterability are of paramount importance. Novel pre-treatment processes have been developed in order to improve sludge dewatering, handling and disposal. This paper discusses the oxidation process utilising the catalytic activation of H(2)O(2) by iron salts, referred to as Fenton's reagent. In previous work, the authors described the experimental laboratory results of H(2)O(2)-oxidation of thickened sludge. Based upon the optimum conditions obtained in these laboratory tests, pilot-scale experiments are conducted. Peroxidation under its optimum conditions, i.e. (i) through addition of 25 g H(2)O(2) kg(-1) DS (dry solids content), (ii) in the presence of 1.67 g Fe(2+)-ions kg(-1) DS, (iii) at pH 3, and (iv) at ambient temperature and pressure, significantly reduces the amounts of sludge and improves the product quality: the amount DS per equivalent inhabitant per day (DS/IE.d) was reduced from 60 to 33.1 g DS/IE.d and the percentage DS of the sludge cake was 47%, which is high compared with the 20-25% achieved in a traditional sludge dewatering facility. An economic assessment for a wastewater treatment plant of 300,000 IE confirms the benefits. Considering the fixed and variable costs and the savings obtained when the sludge is incinerated after dewatering, a net saving of approx. 950,000 Euro per year or 140 Euro per ton DS can be expected.

Hot acid hydrolysis as a potential treatment of thickened sewage sludge.

Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing organic and mineral components and being mechanically dewatered to e.g. 20-25% DS in centrifuges. Both the reduction of the amount of sludge produced and improving its dewaterability are hence of paramount importance. Hot acid hydrolysis can meet these objectives. The current paper describes the results of detailed investigations with respect to acid hydrolysis of thickened sludge (5-6% DS content). A comparison with traditional thermal hydrolysis is also included. As a result of the experimental investigations, it can be concluded that hot acid hydrolysis is efficient in both reducing the residual sludge amounts and improving the dewaterability. Under the proposed optimum conditions it is found that (i) the amount of hydrolysed DS is approximately 70% lower than the initial untreated amount, (ii) the DS-solid content of the dewatered cake is increased from 22.5% (initial untreated) to at least twice this value, (iii) the rate of mechanical dewatering is not significantly affected. The preferential release of ODS into the water phase, and the increased BOD/COD-ratio through hydrolysis, turn this recycle water phase into a possible carbon-source for nitrification/denitrification. Heavy metals and phosphates are also released in the water phase, and can be subsequently precipitated.

Alkaline thermal sludge hydrolysis.

The waste activated sludge (WAS) treatment of wastewater produces excess sludge which needs further treatment prior to disposal or incineration. A reduction in the amount of excess sludge produced, and the increased dewaterability of the sludge are, therefore, subject of renewed attention and research. A lot of research covers the nature of the sludge solids and associated water. An improved dewaterability requires the disruption of the sludge cell structure. Previous investigations are reviewed in the paper. Thermal hydrolysis is recognized as having the best potential to meet the objectives and acid thermal hydrolysis is most frequently used, despite its serious drawbacks (corrosion, required post-neutralization, solubilization of heavy metals and phosphates, etc.). Alkaline thermal hydrolysis has been studied to a lesser extent, and is the subject of the detailed laboratory-scale research reported in this paper. After assessing the effect of monovalent/divalent cations (respectively, K(+)/Na(+) and Ca(2+)/Mg(2+)) on the sludge dewaterability, only the use of Ca(2+) appears to offer the best solution. The lesser effects of K(+), Na(+) and Mg(2+) confirm previous experimental findings. As a result of the experimental investigations, it can be concluded that alkaline thermal hydrolysis using Ca(OH)(2) is efficient in reducing the residual sludge amounts and in improving the dewaterability. The objectives are fully met at a temperature of 100 degrees C; at a pH approximately 10 and for a 60-min reaction time, where all pathogens are moreover killed. Under these optimum conditions, the rate of mechanical dewatering increases (the capillary suction time (CST) value is decreased from approximately 34s for the initial untreated sample to approximately 22s for the hydrolyzed sludge sample) and the amount of DS to be dewatered is reduced to approximately 60% of the initial untreated amount. The DS-content of the dewatered cake will be increased from 28 (untreated) to 46%.Finally, the mass and energy balances of a wastewater treatment plant with/without advanced sludge treatment (AST) are compared. The data clearly illustrate the benefits of using an alkaline AST-step in the system.