The hydraulic retention time on the particle removal efficiency by Daphnia magna filtration on treated wastewater

Abstract

The study of low-cost techniques for the tertiary treatment of wastewater is of global interest; above all low-energy techniques that do not require the use of chemicals. In this study, a wastewater treatment technology based on the filtration by a zooplanktonic population (Daphnia magna) is studied in controlled laboratory and mesocosm experiments for different hydraulic retention times (HRT). The efficiency of the treatment is evaluated in terms of particle removal efficiency. From laboratory experiments, HRT over 12 h and Daphnia concentrations above 50 individuals l -1 guarantee a particle removal efficiency greater than 30 %. However, low HRT of 6 h would require Daphnia concentrations above 70 individuals l -1 in order to obtain a particle removal efficiency of 20 %. The minimum removal efficiency of 2 % was for HRT = 3 h, independent of the Daphnia concentration. In the mesocosm, the growth of Daphnia individuals enhanced Daphnia magna filtering rates and higher removal efficiencies than those in the laboratory for the same HRT range. In the mesocosm experiments E. coli concentrations were reduced to a maximum of 2 logarithmic units. A balance equation model is proposed to predict particle removal efficiencies for varying HRT.

Temperature-driven response reversibility and short-term quasi-acclimation of Daphnia magna

“…Once the spirulina suspension was added to the bottled mineral water, 100 D . magna individuals that were initially obtained from a single brood from the EDAR wastewater treatment plant in Empuriabrava, were carefully introduced into the Plexiglas containers, obtaining a final concentration of 50 individuals L -1 (hereafter ind L -1 ), which is the minimum concentration needed to ensure adequate particle removal efficiency (about 30%) [4,51]. D .…”

Assessment of zooplankton-based eco-sustainable wastewater treatment at laboratory scale

“…These findings suggest that Daphnia (i.e. zooplankton) could be used as a clarifier (reducing the suspended solid content) and disinfectant (reducing the bacterial load), and optimization of these processes would make Daphnia suitable for tertiary wastewater treatment (Maceda-Veiga et al, 2015;Matamoros et al, 2012;Müller et al, 2018;Serra et al, 2014;Serra and Colomer, 2016). It has also been pointed out that Daphnia could contribute to reducing BOD content through the consumption of particulate organic matter (Shiny et al, 2005).…”

Innovative Wastewater Treatment Technologies — The INNOQUA Project

“…D. magna thrive in water temperatures of around 20 • C, although its distribution proves that it can adapt to a broad temperature range (Elenbass, 2013). However, water temperatures above 6 • C are required for D. magna reproduction, whilst in mesocosm experiments, populations experienced seasonal fluctuations, with maximum population densities achieved when water temperatures were between 15 • C and 25 • C (Serra and Colomer, 2016). Due to the ease with which Daphnia are cultivated (Mittmann et al, 2014) and their capacity as filter feeders they can be considered as promising organisms to treat wastewater.…”