Influence of the shear stress and salinity on Anammox biofilms formation: modelling results

Abstract

Anammox biomass has a long duplication time and low yield, thus the process must be operated in reactors with good sludge retention, such as biofilm systems. Therefore, it would be important to research the ability of Anammox biomass to form biofilms under different conditions. The effects of shear stress and salinity (NaCl and CaCl2) on Anammox biofilm formation were studied. Anammox bacteria showed good attachment capacity, with an initial adhesion phase lasting for 5-7 days at the different flow rates tested (Reynolds numbers 54, 63, 188 and 400). A four-parameter model was developed and the experimental data fitted well into the model. The pre-sence of 5 g/L of each of the two salts favoured the formation of Anammox biofilm. The effects of CaCl2 were stronger than those caused by NaCl. 15 g/L of NaCl was detrimental for the biofilm, probably due to an inhibitory effect.

Role of Wall Shear Stress in Cryptosporidium parvum Oocyst Attachment to Environmental Biofilms

“…a decrease in bacterial activity for microorganisms not highly resistant to shear (12,13). High shear forces (such as those experienced during high water flow) also enhance mass transfer between the bulk liquid and the biofilm and can therefore result in thicker biofilm growth (14,15), possibly allowing more efficient oocyst attachment and retention. In addition, temperature can affect bacterial activity and has been documented to cause rapid changes in aquatic microbial community composition, thus altering the morphology and diversity of environmental biofilms (16,17), factors that are likely to affect the efficiency of oocyst attachment and retention to biofilm surfaces.…”

Performance of Anammox Processes for Wastewater Treatment: A Critical Review on Effects of Operational Conditions and Environmental Stresses

“…Similarly, the presence of NaCl was observed to enhance the aggregation of anammox biomass and stimulate anammox activity at NaCl concentrations of 6-15 g/L [162]. In another study [170], the addition of 5 g/L NaCl and CaCl 2 favored the formation of anammox biofilms in an 1 L SBR reactor operated in continuous mode. In addition, the maximal anammox activity was observed only at an NaCl concentration of 5 g/L [171].…”

“…At a smaller scale batch test with 25 mL vials using anammox sludge dominated by "Candidatus Kuenenia stuttgartiensis", the IC 50 value of NaCl was determined at 13.45 g/L [26]. The inhibition of salinity shock on nitrogen removal performance of anammox was generally found in the range from 10-15 g/L [162,166,[168][169][170]172,173]. A complete inhibition of anammox activity was observed in a 10 L MBBR reactor continuously fed with NaCl of 15 g/L [168].…”

Anammox Microbial Activity in Sodium Saline Soil of Former Lake Texcoco, Mexico

“…Anammox microorganisms constitute a distinct phylogenetic group of bacteria, predominantly within the order of the Planctomycetales (Kartal et al 2013). They are especially characterized by their Anammoxosome, a cell compartment where Anammox metabolism takes place, and by their very slow rate of division (Fuers et al 2006, Fernández et al 2014.…”