In the paper concepts for wastewater treatment of the future are discussed by the use of a) one flow diagram based on established, compact, proven technologies (i.e. nitrification/denitrification for N-removal in the mainstream) and b) one flow diagram based on emerging, compact technologies (i.e. de-ammonification in the main stream).The latter (b) will give an energy-neutral wastewater treatment plant, while this cannot be guaranteed for the first one (a). The example flow diagrams show plant concepts that a) minimize energy consumption by using compact biological and physical/chemical processes combined in an optimal way, for instance by using moving bed biofilm reactor (MBBR) processes for biodegradation and high-rate particle separation processes, and de-ammonification processes for N-removal and b)maximize energy (biogas) production through digestion by using wastewater treatment processes that minimize biodegradation of the sludge (prior to digestion) and pretreatment of the sludge prior to digestion by thermal hydrolysis. The treatment plant of the future should produce a water quality (for instance bathing water quality) that is sufficient for reuse of some kind (toilet flushing, urban use, irrigation etc.). The paper outlines compact water reclamation processes based on ozonation in combination with coagulation as pretreatment before ceramic membrane filtration. In the paper concepts for domestic wastewater treatment plants of the future are discussed by the use of a) one flow diagram based on established, compact, proven technologies (i.e. nitrification/denitrification for N-removal in the mainstream) and b) one flow diagram based on emerging, compact technologies (i.e. de-ammonification in the main stream).The latter (b) will give an energy-neutral wastewater treatment plant, while this cannot be guaranteed for the first one (a). The example flow diagrams show plant concepts that a) minimize energy consumption by using compact biological and physical/chemical processes combined in an optimal way, for instance by using moving bed biofilm reactor (MBBR) processes for biodegradation and high-rate particle separation processes, and de-ammonification processes for N-removal and b)maximize energy (biogas) production through digestion by using wastewater treatment processes that minimize biodegradation of the sludge (prior to digestion) and pretreatment of the sludge prior to digestion by thermal hydrolysis. The treatment plant of the future should produce a water quality (for instance bathing water quality) that is sufficient for reuse of some kind (toilet flushing, urban use, irrigation etc.). The paper outlines compact water reclamation processes based on ozonation in combination with coagulation as pretreatment before ceramic membrane filtration.