Control of the biofouling bryozoan, Plumatella repens, using pulsed chlorine treatment

Abstract

Bryozoans are common biofoulers of underdrain filter nozzles in rapid gravity filters in water treatment works. A potential method for controlling bryozoan biofouling is the use of chlorine in backwash water. Repeatedly exposing bryozoan colonies with chlorine for 20 min every 24 h in an experimental setting, to replicate what would occur if the backwash was chlorinated, caused significant reduction in colony growth and size. After 10 days repeated treatment in good conditions for bryozoan propagation, the EC 50 (the chlorine concentration required to decrease growth such that treated colonies were half the size of control colonies) was 1.6 ppm (SE 0.3). In suboptimal conditions for propagation, the impact of chlorine was greater. The majority of colonies treated with 1 ppm and above did not grow or even decreased in size over 5 days. However, a chlorine concentration of 5 ppm was necessary, even in sub-optimal conditions, to ensure all colonies decreased in size over 5 days of treatment; this is too high to be acceptable to water companies due to the risk of carcinogenic by-products. Nevertheless, the observed decline in feeding activity of bryozoans exposed to chlorine levels [1 ppm suggests that repeated backwashing with chlorine may cause colony death over time, especially in sub-optimal conditions. Chlorine backwashes may therefore be an effective long-term control strategy, especially in locations such as rapid gravity filters where it is suggested that upstream processes are likely to create sub-optimal conditions for bryozoan growth.

Crayfish invasion facilitates dispersal of plants and invertebrates by gulls

“…Plumatellid bryozoans are frequently recorded in waterbird excreta (Brochet, Gauthier‐Clerc, et al., ; Green et al., ), but to our knowledge, this is the first confirmation that birds are vectors for alien bryozoans such as P. vaihiriae , although this is considered likely for other aliens such as Pectinatella magnifica (Balounová, Pechoušková, Rajchard, Joza, & Šinko, ). The ability of bryozoans to disperse by birds may increase the economic costs they impose through biofouling of pipes and pumps (Mant, Moggridge, & Aldridge, ). It is likely that the Plumatella statoblasts we recorded became stuck onto P. clarkii via mud.…”

Nitric oxide–secreting probiotics as sustainable bio-cleaners for reverse osmosis membrane systems

“…In a full-scale RO plant, Hoek and co-workers renewed the methodology of disinfection followed by chlorination, microfiltration, and dechlorination along with ultraviolet (UV) irradiation, chlorine dioxide (ClO 2 ), and granular activated carbon (GAC) to prevent befouling on the downstream process in RO membrane (Fujiwara and Matsuyama 2008). The pre-treatment with ultraviolet was not effective, whereas ClO 2 and GAC performed satisfactorily, even though ClO 2 destroys certain membranes (Mant et al 2013;Ghosh et al 2019). 2,2-Dibromo-3-nitrilopropioamide (DBNPA), non-oxidative biocide, can similarly be used to inhibit or eradicate the difficulties owing to the accumulation of biofouling and confirm the long-term performance of the RO system (Bertheas et al 2009).…”

The larval morphology and the effects of sound frequencies on the settlement behaviour of the biofouling Bryozoan: Watersipora subatra

“…The authors concluded that improvements of anti-fouling methods would substantially reduce the annual budget spent on biofouling and the savings would eventually cover the cost of research and implementation of new techniques. Similarly, the UK water industry spent £1.49M over a four-year period due to persistent foulers; with common, biofouling bryozoans being discovered growing on rapid gravity filters within these facilities reducing the effectiveness of the filter (Mant et al, 2011;Mant et al, 2013).…”