Agroindustrial Wastewater Treatment with Simultaneous Biodiesel Production in Attached Growth Systems Using a Mixed Microbial Culture

Olga Tsolcha,Savvas Genitsaris,George Aggelis,Christos Akratos,Athanasia Tekerlekopoulou,Dimitrios Vayenas,Maria Moustaka-Gouni

doi:10.3390/w10111693

Olga Tsolcha, Savvas Genitsaris + Show 5 more

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https://doi.org/10.3390/w10111693

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Abstract

The use of cyanobacteria in biological wastewater treatment technologies can greatly reduce operation costs by combining wastewater bioremediation and production of lipid suitable as biodiesel feedstock. In this work, an attached growth system was employed to achieve the above-mentioned dual objective using a mixed microbial culture dominated by Leptolyngbya and Limnothrix species in diverse heterotrophic consortia. Kinetic experiments on different initial pollutant concentrations were carried out to determine the ability of the established culture to remove organic load (expressed by d-COD, dissolved-Chemical Oxygen Demand), N and P from agroindustrial wastewaters (dairy, winery and raisin). Biomass and oil productivity were determined. It was found that significant removal rates of nutrients were achieved in all the wastewaters examined, especially in that originated from winery in which the highest d-COD removal rate (up to 97.4%) was observed. The attached microbial biomass produced in winery wastewater contained 23.2% lipid/biomass, wt/wt, which was satisfying. The growth in the dairy wastewater yielded the highest attached biomass productivity (5.03 g m−2 day−1) followed by the mixed effluent of winery-raisin (4.12 g m−2 day−1) and the winery wastewater (3.08 g m−2 day−1). The produced microbial lipids contained high percentages of saturated and mono-unsaturated fatty acids (over 89% in total lipids) in all substrates examined. We conclude that the proposed attached growth photobioreactor system can be considered an effective wastewater treatment system that simultaneously produces microbial lipids suitable as biodiesel feedstock.

Highlights

One current challenge for ecological engineering is to develop economically feasible technologies to treat wastes as a biomass source and, ideally, transform them into useful byproducts.Various physicochemical treatment methods demand large amounts of energy, chemicals, andWater 2018, 10, 1693; doi:10.3390/w10111693 www.mdpi.com/journal/waterWater 2018, 10, 1693 manpower
Microscopic analysis (Figure 1) showed aggregates of cyanobacterial trichomes associated with attached colonies of heterotrophic bacteria and large planktonic bacterial cells
The trichomes exhibited the morphological features of the genera Leptolyngbya and Limnothrix (Figure 1b)

Summary

Introduction

One current challenge for ecological engineering is to develop economically feasible technologies to treat wastes (liquid or solid) as a biomass source and, ideally, transform them into useful byproducts.Various physicochemical treatment methods demand large amounts of energy, chemicals, andWater 2018, 10, 1693; doi:10.3390/w10111693 www.mdpi.com/journal/waterWater 2018, 10, 1693 manpower. The biological treatment of wastewaters is considered to be a more environmental friendly and cost-effective approach. The use of microalgae and cyanobacteria can aid environmental mitigation as they produce lipids suitable for second and third generation biofuels [2,3]. Applications such as wastewater treatment and biofuel production can be combined [4]. In these combined systems effluents are considered as a source of nutrients rather than as waste material, while the biomass produced may be converted into energy

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