Exploring Different Pretreatment Methodologies for Allowing Microalgae Growth in Undiluted Piggery Wastewater

Abstract

The overapplication of manure on agricultural soils leads to nitrogen and phosphorus discharge into the aquatic environment, resulting in serious eutrophication problems and decreased water quality. Piggery wastewater (PWW) can be treated by microalgae to recycle nutrients, but the toxic levels of ammonia and organic matter hinder their growth. Fresh water is usually used to dilute PWW, but it is a scarce resource. The implementation of a pretreatment step before microalgae-based treatment could make PWW suitable for microalgae growth. Electrocoagulation, ammonia stripping, photo-Fenton, and constructed wetlands were evaluated as pretreatment methods to reduce ammonia, chemical oxygen demand (COD), color, and total suspended solids. Moreover, the pretreated PWWs were tested to grow the microalga Tetradesmus obliquus. Photo-Fenton showed the best results among the other pretreatments, achieving removal efficiencies above 90%, except for ammonia. This resulted in T. obliquus being capable of growing on undiluted PWW, even at higher ammonia levels, achieving similar biomass productivity to synthetic medium (66.4 ± 17.8 mg·L−1·day−1 and 60.1 ± 10.4 mg·L−1·day−1, respectively) almost doubling with pH control (116.5 mg·L−1·day−1). Thus, this pretreatment seems to be the most promising one to incorporate into microalgae-based treatment systems and must be further explored.

Use of anaerobic filters filled with waste from the ceramics industry in swine wastewater treatment

“…Color is associated with the presence of dissolved solids (VON SPERLING, 2005;FERREIRA et al, 2022) and, although it is not necessarily related to problems of contamination of water bodies, it causes problems of an aesthetic nature and hinders light penetration. In addition, it may be related to recalcitrant compounds that, in this case, in general, are toxic to the aquatic community (PIVELI; KATO, 2005; BENDER; SOUZA; VIDAL, 2019).…”

Unlocking the potential of Euglena gracilis cultivated in piggery wastewater: biomass production, nutrient removal, and biostimulant potential in lettuce and tomato plants

“…The microalga was subjected to cultivation in raw wastewater diluted with tap water (25% raw wastewater:75% tap water, v:v; P25) and in non-diluted Photo-Fenton (PF) pre-treated wastewater. The photo-Fenton process followed a previously established protocol described by Ferreira et al (2022).…”

“…However, this approach is not sustainable, as clean water -a scarce resource -should not be used to dilute contaminated water. An alternative approach proposed byFerreira et al (2022) involves the implementation of pretreatment using advanced oxidation processes, such as photo-Fenton, to minimize the toxicity of PWW, all without the need for freshwater for dilution. Both strategies were employed in the present study and 2022) Kuroda et al (2018).…”

Equilibrium of Ammonia (NH3) and Ammonium (NH4+) during Microalgae Harvesting using Electrocoagulation

“…D. salina culture wastewater containing TAN has the potential to contaminate water bodies if disposed of directly without treatment. In addition to treating D. salina culture wastewater, efforts that can be made when disposing of microalgae culture wastewater include dilution by water [7], but water is a scarce resource [8].…”

“…Untreated microalgae effluent containing nutrients (nitrogen and phosphorus) has the potential to pollute aquatic bodies. Instead of treating microalgae effluent before disposal, water dilution may be used [7], but water is a scarce resource [8].…”