Wastewater heat recovery via heat exchangers and heat pumps constitutes an environmentally friendly, approved and economically competitive, but often underestimated technology. By introducing the spatial dimension in feasibility studies, the results of calculations change considerably. This paper presents a methodology to estimate thermal energy resource potentials of wastewater treatment plants taking spatial contexts into account. In close proximity to settlement areas, wastewater energy can ideally be applied for heating in mixed-function areas, which very likely have a continuous heat demand and allow for an increased amount of full-load hours compared to most single-use areas. For the Austrian case, it is demonstrated that the proposed methodology leads to feasible results and that the suggested technology might reduce up to 17% of the Austrian global warming potential of room heating. The method is transferrable to other countries as the input data and calculation formula are made available. A broad application of wastewater energy with regard to spatial structures and spatial development potentials can lead to (1) increasing energy efficiency by using a maximum of waste heat and (2) a significant reduction of (fossil) energy consumption which results in a considerable reduction of the global warming potential of the heat supply (GWP) if electricity from renewables is used for the operation of heat pumps.

Operation and maintenance of the public sewer system represent key tasks for an operator. Condition assessment is usually conducted by conventional closed circuit television (CCTV) inspection. However, alternative tools such as manhole-zoom cameras (MZCs) and the acoustic technology SewerBatt® are available today. The INNOKANIS project investigates structural and operational condition assessment in the sewer system by means of three MZC models and SewerBatt® to develop a combined optical and acoustic device as a cost-effective alternative to conventional CCTV inspection. The first field trials of the ongoing project were conducted in Austria in 2011. 640 conditions according to EN 13508-2/A1 were investigated and compared against conventional CCTV reports. Individual and combined detection rates for both devices were calculated. Based on the current findings, both MZC and SewerBatt® are effective alternatives to conventional CCTV inspection. In addition, performance is significantly enhanced when both devices are used in combination.

Although the main function of a wastewater treatment plant (WWTP) is to remove various constituents from wastewater it can also serve as a source of energy and other materials. The generated resources can be used either on-site at the WWTP or elsewhere at an adjacent infrastructure. In the course of a current national research project, the possibilities and potentials regarding the integration of WWTPs into local energy supply concepts are being investigated in Austria. Preliminary results show that in particular the amount of thermal energy available exceeds by far the on-site demands of WWTPs. Even on-site electrical energy demands could be self-addressed under certain conditions. This paper describes the estimation of total energy consumption and generation and the related degree of energetic self-sufficiency at certain Austrian WWTPs. Preliminary results regarding the development of a tool for evaluating and optimising on-site and externally supplied use of energy are presented. Finally, the possibilities of energy supply for neighbouring spatial structures are discussed briefly and conclusions drawn about the potential to develop WWTPs as regional energy cells.