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Landfill leachate is characterised by high chemical and biological oxygen demand and generally consists of undesirable substances such as organic and inorganic contaminants. Landfill leachate may differ depending on the content and age of landfill contents, the degradation procedure, climate and hydrological conditions. We aimed to explain the characteristics of landfill leachate and define the practicality of using different techniques for treating landfill leachate. Different treatments comprising biological methods (e.g. bioreactors, bioremediation and phytoremediation) and physicochemical approaches (e.g. advanced oxidation processes, adsorption, coagulation/flocculation and membrane filtration) were investigated in this study. Membrane bioreactors and integrated biological techniques, including integrated anaerobic ammonium oxidation and nitrification/denitrification processes, have demonstrated high performance in ammonia and nitrogen elimination, with a removal effectiveness of more than 90%. Moreover, improved elimination efficiency for suspended solids and turbidity has been achieved by coagulation/flocculation techniques. In addition, improved elimination for metals can be attained by combining different treatment techniques, with a removal effectiveness of 40–100%. Furthermore, combined treatment techniques for treating landfill leachate, owing to its high chemical oxygen demand and concentrations of ammonia and low biodegradability, have been reported with good performance. However, more study is necessary to enhance treatment methods to achieve maximum removal efficiency.

Recovery of proteins and fats from dairy wastewater has two advantages: the recovery process results in a pretreatment of wastewater prior to discharge to municipal sewers; and the recovered sludge can be used as a food additive. Carboxy Methyl Cellulose (CMC) is commonly used for the treatment of dairy wastewater after reducing the wastewater to pH 4.2. A novel application of a non-toxic cationic biopolymer – chitosan – is evaluated as a substitute for CMC. The results indicate that chitosan can achieve results similar to the CMC process even at pH as high as 5.3. Thus, the novel method can save up to 50 % of pH-adjusting chemicals requires for both for acidification and neutralisation. The process sludge contains valuable components which have been evaluated and found to be suitable as a food additive. A stable demand for chitosan is also expected to solve the existing shrimp-shell waste disposal problems along the west and north Norwegian coasts. The process is found to be both environmentally and economically attractive for all partners.

Abstract:Coagulation is an essential process for the removal of suspended and colloidal material from water and wastewater. However, no comprehensive or universally accepted mathematical description of the process has been developed so far. Therefore, process optimization and control is usually based on data from jar tests and simple flow-proportional dosing concepts, while more accurate concepts based on water quality parameters that can be measured online are emerging. In addition, there have been attempts to develop software sensors and control schemes that involve advanced mathematical analyses of these parameters. The paper presents an overview of the parameters and physical sensors that are used for feed-forward and feed-backward control schemes and the experiences that have been made with their implementation. Moreover, the development and use of software sensors is described. Finally, the practical applications of different control techniques are given in order to illustrate the state of the art of coagulation control. Some thoughts about research needs conclude this review.

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