Upgrading of sewage treatment plant by sustainable and cost-effective separate treatment of industrial wastewater

TLDR

The plant was upgraded with a separate industrial wastewater line, using a UASB reactor for biogas, followed by a struvite (Phospaq) reactor and a single‑stage granular sludge nitritation/anammox process, implemented through a public‑private partnership. The separate treatment proved more cost‑, area‑, and energy‑efficient, operated stably for three years, produced struvite usable as fertilizer, tolerated high nitrite without inhibiting anammox, and reduced reactor volume by 17× while saving about 1.5 GWh annually.

Abstract

The Olburgen sewage treatment plant has been upgraded to improve the effluent quality by implementing a separate and dedicated treatment for industrial (potato) wastewater and reject water. The separate industrial treatment has been realized within a beneficial public-private partnership. The separate treatment of the concentrated flows of industrial wastewater and sludge treatment effluent proved to be more cost-efficient and area and energy efficient than a combined traditional treatment process. The industrial wastewater was first treated in a UASB reactor for biogas production. The UASB reactor effluent was combined with the reject water and treated in a struvite reactor (Phospaq process) followed by a one stage granular sludge nitritation/anammox process. For the first time both reactors where demonstrated on full scale and have been operated stable over a period of 3 years. The recovered struvite has been tested as a suitable substitute for commercial fertilizers. Prolonged exposure of granular anammox biomass to nitrite levels up to 30 mg/l did not result in inhibition of the anammox bacteria in this reactor configuration. The chosen option required a 17 times smaller reactorvolume (20,000 m(3) less volume) and saves electric power by approximately 1.5 GWh per year.