The untreated primary sludge produced in the sewage treatment plant with a dry matter content of about 4 – 5 % by mass is stabilized by means of different technical methods, dried to a DM content of 80 – 85 % and serves as raw material for further processing. Predominantly, municipal sewage sludge is pelleted, the composition of which is relatively homogeneous on account of its origin. Basically, industrial sewage sludge can also be pelleted, yet its structure and composition may vary a lot.

Sewage sludge is a suitable resource for phosphorus. Because of the presence of harmful substances, particularly heavy metals, the application to agricultural land is seen more and more critically and is already partially banned. The aim is therefore to treat sewage sludge in a way that harmful substances are eliminated and nutrients, particularly phosphorus, can be recovered. The recovered phosphorus has to be suitable as a potential fertiliser. It has to have a low concentration of heavy metals and a good accessibility for plants, which means, that phosphorus has to be present in its soluble form. At the moment there is no efficient recovery procedure on a large scale available, which offers a high recovery potential, an elimination of harmful substances and a product with a good uptake by plants.

The recent years WTE Wassertechnik GmbH has realised interesting projects with its engineers, it has realised big projects, has been looking for technical challenges, has mastered these and year by year new superlatives followed. So, for example, the infrastructure project in Zagreb, the biggest at that time in Europe, different sewage plants with more than 2 million PE (Warsaw, Istanbul), the second largest sewage plant with membrane technology, the biggest primary settlement tank with selfrotary covers, the biggest pump performances, the biggest mud throughput, the biggest sludge treatment with thermal pressure hydrolysis and a lot of other projects were realised.

Lonza Engineering Ltd. Basel, Switzerland (member of Lonza Group AG) and its wholly owned subsidiary Lonza Guangzhou Engineering & Consulting Co., Ltd., China provides customer oriented services with a professional and experienced engineering team. The company has more than 15 years of project management experience in China.

Wastewater treatment plants generate sewage sludge as a by-product of the physical, chemical and biological processes used during the wastewater treatment. In these plants, anaerobic digestion has been used, for more than a century, to stabilize the sewage sludge produced. At the present time, most anaerobic digesters are operated at mesophilic conditions. However, the need to improve the process feasibility, by means of increasing the biogas yield and reducing the sludge disposal costs, has increased the interest in thermophilic conditions. In this topic, the thermophilic anaerobic digestion offers some potential advantages over conventional mesophilic anaerobic digestion: (i) an increase of the biological and chemical reaction rates, (ii) an increase of the organic matter removal, (iii) a higher solubilization of the particulate organic matter and (iv) an enhancement of the pathogenic organism destruction. Further Authors: M. Peces - Department of Chemical Engineering, University of Barcelona S. Astals - Department of Chemical Engineering, University of Barcelona

In 2007, 1 100 000 tons of sewage sludge were produced in France. This figure is constantly increasing and sludges have to be eliminated. Four disposal routes are currently possible: land spreading (directly or after composting), incineration, incineration with household wastes and landfilling. These different disposal routes as well as the sludge treatments produce greenhouse gases (GHG). To help stakeholders to better understand the carbon footprint of sludge treatment and disposal options, we developed a tool called GESTABoues. Further Author: A.L. Reverdy - Irstea

Bioplastics, in particular polyhydroxyalcanoates (PHAs), are widely studied as biodegradable materials for substitution of oil derived polymers. However, their production at an industrial scale is still limited due to high production costs. In addition, industrial PHAs recovery needs the use of large volumes of organic solvent like chloroform, which is not convenient for environmental safety (Byrom, 1994). Bosco and Chiampo (2010) reported four ways to reduce these costs including new cheap substrates, new fermentative strategies, new recovery and purification steps, and new microorganisms for accumulation of high PHA concentrations. Further Authors: C. Rondel C.E. Mercato-Romain V. Dossat-Létisse D. Lefebvre

A good way for utilizing municipal sewage sludge is its use on agriculture lands after composting. The fate of sewagesludge is unsolved, its large quantity is cumulated on the territories of sewage cleaning plants. We can solve seriousenvironmental problems with sewage sludge treatment, however there are some risks, since sewage sludge may containheavy metals in high rate.In the Nyírség region of Hungary there are mostly acidic sandy soils with low humus content. Because of the decreasingquantity of livestock manure, the subsequent delivery of organic matter into the soils could be problematic. Further Author: Gy. Füleky - Szent István University

Gasification is a technology that can replace traditional management alternatives used up to date to deal with this waste(landfilling, composting and incineration) and which fulfils the social, environmental and legislative requirements. The main products of sewage sludge gasification are permanent gases (useful to generate energy or to be used as rawmaterial in chemical synthesis processes), liquids (tars) and char. One of the main problems to be solved in gasificationis tar production. Tars are organic impurities which can condense at relatively high temperatures making impossible touse the produced gases for most applications. Further Authors: E. Roche - Universidad Politécnica de Madrid M.E. Rodríguez - Universidad Politécnica de Madrid

Municipal solid waste is a very complex and heterogeneous system made of a wide range of materials. Among thesematerials, more than 50% are biodegradable and can be valorized through treatments based on anaerobic biologicalprocesses to produce biogas, a renewable source of energy. The ligno-cellulosic fraction of waste, mainly constituted by paper and cardboard (25%), plays an essential role in the production of biogas and is responsible for almost 80% ofbiogas emission (Eleazer, et al., 1997). Further Authors: T. Serain - Irstea, France

Pharmaceuticals are essential to the delivery of health care in any given population or country. They cut across all major areas of health care delivery and their absence or inadequate supply has always led to loss of confidence in the health care system (MOH, 2004a). The main goal of this research project is to assess the system of managing waste from pharmaceuticals in hospitals and homes in Ghana.

Phosphorus is an important element for the fertility of soils. The actual practise in waste elimination causes important losses of phosphorus coming from the incineration of sewage sludge and then burning of bone and meat meal in plants, which do not allow recovering the phosphorus.

In the Canton of Zurich, approximately 100,000 tonnes of drained sewage sludge from 104 sewage treatment plants are currently burned in 9 waste management facilities. The methods used include co-incineration in waste incineration plants, dedicated incineration and drying with subsequent incineration in a cement works.

The mechanical sewage sludge drainage is a minimum treatment level for sludge treatment in large cities, as the sludge can generally not, or not entirely, be transferred to agricultural recycling due to the high pollution and the large quantity. Further treatment of the sewage sludge in the form of drying and/or incineration must be examined in the individual case, with regard to efficiency and disposal safety.

Municipal wastewater sludge, before any management is stabilized in course of biological treatment (an aerobic or anaerobic stabilization) or by chemical methods in wastewater treatment plant. After stabilization, wastewater sludge is dewatered and passed to specialized companies for further management. In recent years, an extension of sludge treatment process with drying and incineration becomes more and more popular.

The use of sewage sludge in agriculture is being questioned, in particular because of the inorganic and organic pollutants, including traces of drugs and hormones. Therefore, restrictions are gradually being introduced in European countries, with a trend towards mineralization of sludge and hence solutions envisaging thermal treatments.