Analysis of the wastewater heat recovery potential considering its impact on the wastewater treatment plant
- 1. IRH Ingenieur Conseil, Antea Group, Ludres (France)
- 2. IRH Ingenieur Conseil, Antea Group, Toulouse (France)
- 3. Eurometropole de Strasbourg, Strasbourg (France)
Description
Wastewater contains considerable amounts of energy that can be recovered by means of a heat pump and a heat exchanger. Wastewater heat recovery potential could be estimated by knowing the flow rate within the sewer system and the difference in temperature that can be extracted ΔT (deg. C). Most cartography studies of the wastewater recovery potential assume the extraction temperature difference to be 4,5 deg. C, as it is the average value among existing operations in France. However, this value does not consider the potential negative impact on wastewater treatment plant (WWTP). In fact, recovering too much heat from wastewater within the sewer system could lead to a decrease in temperature at the WWTP inlet. As a consequence, it would lower the quality of biological processes concerning nitrification and denitrification. According to literature, a decrease in temperature of 1 deg. C at the WWTP inlet does not represent a high risk in the deterioration of biologic processes as long as the treatment plant does not function at its capacity limit and the temperature does not drop below its dimensionality limit. Respecting these conditions at the inlet of the WWTP La Wantzenau, main wastewater treatment plant of the Eurometropole de Strasbourg, the difference in temperature that can be extracted ΔT (deg. C) was estimated at any point of the sewer network. This way a recovery potential was calculated taking into account the impact on the WWTP and, therefore, making it comparable with a theoretical potential determined with a recovery of 4,5 deg. C in all channels. The results showed that an extraction of 4.5 deg. C generates temperature decreases higher than 1 deg. C at the inlet of the La Wantzenau and overestimates the recovery potential especially downstream of the network. The recovery potential including the impact on the WWTP is reduced, but more accurate with regard to the initiation of recovery projects. (authors)
Abstract (French)
Les eaux usees vehiculent des quantites elevees d'energie qui peuvent etre recuperees au moyen d'une pompe a chaleur et d'un echangeur thermique. L'estimation du potentiel de recuperation de chaleur des eaux usees demande de connaitre essentiellement leur debit et la quantite de chaleur a extraire ΔT (deg. C). Pour cette derniere, la valeur de 4,5 deg. C'est couramment utilisee pour des etudes de cartographie energetique des systemes d'assainissement, car elle represente la valeur moyenne des operations existantes en France. Toutefois cette valeur ne prend pas en compte le potentiel impact sur la station de traitement des eaux usees (STEU). En effet, recuperer trop de chaleur dans le reseau d'assainissement peut provoquer une diminution de la temperature des effluents au niveau de la STEU. Cet abaissement peut compromettre la qualite des processus biologiques de nitrification et denitrification. D'apres la litterature, une baisse de 1 deg. C en entree de STEU ne representerait pas de risque de degradation des procedes biologiques a condition que la station ne fonctionne pas au maximum de sa capacite et que la temperature ne descende pas au-dessous de la temperature minimale de dimensionnement. En respectant ces conditions a l'entree de La Wantzenau, principale STEU de l'Eurometropole de Strasbourg, les quantites de chaleur a extraire ΔT (deg. C) dans tout point du reseau ont ete estimees. Cela a permis de calculer un potentiel de recuperation qui tient compte de l'impact sur la STEU et de le comparer avec un potentiel theorique calcule avec une extraction de 4,5 deg. C. Les resultats montrent que, sur certains points, l'extraction de 4,5 deg. C provoque des variations de temperature superieures a 1 deg. C en entree de STEU et conduit a des surestimations du potentiel de recuperation. La puissance de recuperation de chaleur calculee, en integrant l'impact previsionnel sur La Wantzenau, est ainsi plus reduite, mais constitue un reel interet pour identifier des projets de recuperation qui semblent plus realistes. (auteurs)Additional details
Additional titles
- Original title (French)
- Analyse du potentiel de recuperation de chaleur des eaux usees prenant en compte l'impact sur la STEU
Publishing Information
- Journal Title
- TSM. Techniques Sciences Methodes, Genie Urbain Genie Rural
- Journal Issue
- no.3
- Journal Page Range
- p. 63-71
- ISSN
- 0299-7258
- CODEN
- TSMREA
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 53050210
- Subject category
- S42: ENGINEERING;
- Descriptors DEI
- CAPACITY; FLOW RATE; HEAT EXCHANGERS; HEAT RECOVERY; WASTE HEAT UTILIZATION; WASTE WATER; WATER SOURCE HEAT PUMPS; WATER TREATMENT PLANTS
- Descriptors DEC
- ENERGY RECOVERY; HEAT PUMPS; HYDROGEN COMPOUNDS; LIQUID WASTES; OXYGEN COMPOUNDS; WASTE PRODUCT UTILIZATION; WASTES; WATER
Optional Information
- Notes
- 14 refs.