Proceedings

Nutrient Removal with Microalgae – Reduction of the Effluent Concentration from Wastewater Treatment Plant

Wawilow, T.1; Hasport, N.1, Theilen, U1 and Thomsen C.2
1THM – University of Applied Sciences – ZEuUS, Germany
2 Phytolutions GmbH, Germany

(free)

Abstract:

An alternative, environmentally sustainable method to remove nutrients from wastewater is to integrate an algae-mediated wastewater treatment to reduce nutrient loads to preserve water bodies from eutrophication and generate effective biomass. Compared with conventional treatment methods the generated microalgae biomass is more energetic and rich in content with phosphorous (P) and nitrogen (N). Therefore, a tertiary biotreatment coupled with the production of potentially valuable biomass, which can be used for energetic or material purposes, is an efficient alternative to avoid using chemicals for the removal of phosphorus via precipitation and flocculation. Algae species Scenedesmus was applied for wastewater treatment and had proven abilities of removing nitrogen and phosphorous in retention time of 24 hours. In this study, a photobioreactor (PBR) was implemented for large-scale research to treat the wastewater treatment plant (WWTP) effluent while microalgae growth rate, nutrition removal as well as operational and external conditions were evaluated. Moreover, the biomass was separated and methane potential tests were conducted using microalgae as substrate.

Keywords

effluent concentration, microalgae, nutrient removal, photobioreactor, wastewater treatment

Introduction

Recent national and European regulations decrease the discharge limits of contaminants from wastewater treatment plants (WWTP) and in particular the regulation focused on nutrient removal (N and P) in order to reduce the eutrophication/contamination in water bodies.

Usually techniques in wastewater treatment to reduce N or P are biological or physico-chemical methods. To avoid using chemicals for the phosphorous removal a cost-effective alternative and environmental treatment to reach more stringent limits is to integrate a PBR for algae-mediated wastewater treatment as last step of biological treatment. In the study at the WWTP in Rotenburg-Braach, Germany, a part of effluent from plant was treated by microalgae in PBR from Phytolutions company, to demonstrate the alternative process and improve to avoid using chemicals for phosphorous removal.

Compared to biological process in WWTP the microalgae depend on sunlight for higher growth rates and for faster elimination rates because microalgae are like plants and require sunlight, CO2 and water (nutrients) to growth. During the photosynthesis microalgae convert the solar energy into chemical energy and produce oxygen and biomass. Furthermore, microalgae require nutrients to generate biomass particularly nitrogen and phosphorous and many other micronutrients that are involved in wastewater streams. The objective of this study was to use microalgae to remove nutrients from WWTP effluent in order to prevent eutrophication. Algae species Scenedesmus was applied for wastewater treatment and had proven abilities of removing N and P in retention time of 24 hours. The green microalgae Scenedesmus has shown extraordinary vitality in urban wastewaters and these freshwater algae tolerate a wide range of temperature and pH. The fast growing was limited by sunlight. The Hessian Ministry of the Environment and the Stadtwerke Rotenburg are funding the ongoing research project to implement a photobioreactor for large-scale research to treat the WWTP effluent with microalgae. Moreover, the biomass was separated and methane potential tests were conducted using microalgae as substrate.

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