Introduction of struvite and constructed wetlands for digestate treatment and local reuse in Turkey

Resource recovery from waste(water) and their local reuse can be very interesting for agro and food industries. By doing so resources such as energy, water and nutrients can be reused, thus enabling the closing of cycles. Cow manure is digested at the Sütaş dairy factory in Uluabat, Karacabey (part of the Sütaş group) to produce energy (steam, electricity) for internal use. In this project the digestate of this digester is separated into a solid and liquid fraction after which the liquid fraction will be treated with constructed wetlands prior to discharge or agricultural reuse. Phosphorus in the form of struvite will be recovered as well and used with the solid fraction to produce an organic fertilizer. The recovered resources can be used by farmers in the vicinity of the dairy factory, thus closing cycles.

The Sütaş dairy factory in Uluabat, Karacabey (part of the Sütaş group) operates the entire dairy chain, from producing animal feeds and owning cows to producing dairy products for in the store. The Sütaş group has several subsidiaries that provide services for the group. The Sütaş dairy factory produces dairy products; Enfaş Energy provides wastewater treatment and energy recovery services for the dairy factory; and Tarfaş is the farm company and produces (veterinary) services and knowledge on dairy cattle keeping. An 1900 m3 digester has been constructed at the Sütaş dairy factory to produce electricity (2.2 MW) and steam for internal use. The digestate is separated by a screw separator after which the liquid fraction is stored in a tank prior to discharge to an oxidation ditch, lagoons or occasional use by neighbouring farmers. The solid fraction is stored, discarded or sometimes used for agriculture by neighbouring farmers.

During this project a pilot at the Sütaş dairy factory will be constructed to further recover resources from the digestate. Phosphorus will be recovered in the form of struvite. The liquid fraction will be treated with constructed wetlands to produce effluent that can be safely discharged to the environment or reused in agriculture for irrigation purposes. The solid fraction combined with the struvite can be processed to produce an organic fertilizer. The main objective of the project is to introduce and promote natural, plant based wastewater treatment systems (“Constructed Wetlands”) in Turkey and  struvite formation as valuable treatment steps after anaerobic digestion. This pilot will form a stepping stone for upscaling and will demonstrate the potential of resource recovery from residue streams in agro and food industries in an economic and environmentally sound manner.

The cooperation between LeAF, BV watersolutions (part of BrinkVos Water) and ees-International creates a partnership that enables the recovery of resources from, and tertiary treatment of, waste(water) in a cost-effective way. The partnership results in complementary knowledge, experience and technologies. The cooperation in this project will ensure that resources (Energy, Phosphorus, Nitrogen, Organic Carbon and Water) contained by dairy-factory wastewater and manure from cattle farms in Uluabat, Turkey, will be recovered and re-used, thereby ensuring full treatment of the wastewater prior to discharge.

LeAF is the overall coordinator of this project. It further contributes to the project with its knowledge on residue treatment, recovery of resources and anaerobic digestion, as well as its close ties with Wageningen UR. These are especially relevant for the pilot on recovering phosphorus (in the form of struvite) from digestate.


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