Clonal variation in reproductive response to temperature by a potential bulking control agent, Lecane inermis (Rotifera)

Abstract

The novel idea of using rotifers Lecane inermis (Rotifera, Monogononta) as a tool to overcome activated sludge bulking generates an on-going need to study rotifer biology. The results of biological research on rotifers can serve to improve the method so that it can be most effective when applied in treatment plants. The aim of this study was to test the effect of temperature on four selected rotifer clones originating from different treatment plants. The rate of population development from a single individual (parthenogenetic female) during a 10-day experiment was measured at three temperatures: 8, 15 and 20 W C. The temperatures used reflect the annual temperature distribution in the majority of municipal wastewater treatment plants in the temperate zone. The growth rate coefficient (r) and doubling time (tD) were calculated for each clone. Under the most favourable conditions (20 W C), r values varied between 0.41 and 0.47 d and doubling time between 1.5 and 1.7 d. At a temperature of 15 W C, the doubling time was approximately two times longer (2.5-3.4 d). The strongest intraspecific variations were observed at the lowest temperature of 8 W C. At this temperature, one of the clones almost failed to proliferate, and another exhibited a doubling time of 7.9 d. The doubling times were a few times greater for the remaining two clones (60 d for Lk1, 33.3 d for Lk4). These results could be very useful in predicting the chances that the rotifers would survive in a biological reactor in a wastewater treatment plant at the temperatures used in these reactors.

Lecane tenuiseta (Rotifera, Monogononta) as the best biological tool candidate selected for preventing activated sludge bulking in a cold season

“…As is known from our earlier experiments, the growth rate of L. inermis is extremely sensitive to temperature decreases. At 8˚C, three of four examined strains completely ceased proliferation [7]. Growth rate dependence on temperature in Lecane sp.…”

“…As Fiałkowska and colleagues [7] have shown, the growth rate of Lecane inermis drastically decreases as the temperature decreases below 10˚C [6]. At the lowest tested temperature (8˚C), only one of four clones maintained its ability to reproduce.…”

“…(2016) [1][2][3][4][5][6][7][8] www.deswater.com doi: 10.1080/19443994.2016.1192565 due to seasonally low air temperature and/or snowmelt [1]. There are some discrepancies between the observations made in treatment plants where M. parvicella growth is promoted at low temperatures [1][2][3] and laboratory research regarding the growth kinetics of the two strains of this bacterium in pure culture, showing that the optimum temperature for its growth is above 22˚C [4].…”

“…As the positive effect of different rotifers on the properties of sludge has already been confirmed [7][8][9][10][11][12], the search for rotifers that are best adapted to function at low temperatures is needed to optimise their beneficial effects. To determine whether rotifer species already possess the capability to perform better at low temperatures, we conducted a set of selection experiments at 8, 15 and 20˚C.…”

Foam-forming bacteria in activated sludge effectively reduced by rotifers in laboratory- and real-scale wastewater treatment plant experiments

“…The minimum temperature at which L. inermis can sustain a positive growth rate is 8 °C, but this has only been observed in one of the four clones of this species (Fiałkowska et al 2011). The optimal temperature at which this rotifer has exhibited its highest growth rate is 30 °C (Walczyńska et al 2016), so at lower temperatures, they require relatively old sludge to reach the density at which they can limit the overproliferation of filaments.…”