Improving the biomass retention and system stability of the anammox EGSB reactor by adding a calcium silicate hydrate functional material.

Improving the biomass retention and the sludge system stability to promote the full-scale application of anammox process is the focus of current related research. In this study, a calcium silicate hydrate functional material with calcium-releasing ability and weak alkalinity was used for an enhanced anammox process. In the long-term operation, an increase in the nitrogen removal rate (NRR) from 2.75 to 13.38 gN/L/d was achieved after 50 days of operation, with the abundance of Candidatus Kuenenia increased from 40.1 % to 47.0 %. The anammox activity was strengthened from 0.089 to 0.55 gN/gVSS/d over 50 days, with a growth rate being fitted at 0.0310 d-1. The resilience of the EGSB anammox system after inhibitions was investigated by substrate shock and low pH shock in long-term operation and batch test. Besides that, the phosphorus removal efficiency of the reactor reached up to 90 % under the positive effect of functional material. The functional material was shown to continuously provide calcium in the long-term for the reaction of hydroxyapatite (HAP) formation, which further improved the granular properties of the sludge and the biomass retention ability of the reactor. The promotion effect of functional material on the sludge granulation and anammox microbes retaining efficiency was the key for a high-resilience anammox EGSB reactor.

Coating of Silica Nanolayers on Carbon Nanofibers via the Precursor Accumulation Method.

Surface modification of nanocarbons, for example, by coating with oxide nanolayers, is a research topic of significant interest because of the drastic changes in the physicochemical properties of the modified nanocarbons. One simple method of creating these oxide nanolayer coatings on nanocarbons is the precursor accumulation (PA) technique, which entails the following: (1) a precursor solution is added dropwise onto nanocarbon powder; (2) the solvent is dried, leaving the accumulated precursor on the nanocarbon surface; and (3) hydrolysis or decomposition of the precursor in air leads to the formation of oxide nanolayers on the nanocarbons. In this study, tetraethoxysilane (TEOS) was used as a precursor for coating silica nanolayers onto carbon nanofibers (CNFs). TEOS is so stable that it hardly undergoes hydrolysis on the surface of pristine CNFs. By treating CNFs with H2SO4/HNO3, acidic functional groups were introduced onto the CNF surfaces. Silica nanolayers were successfully synthesized on these acid-treated CNFs via PA coating because the acidic functional groups catalyzed the hydrolysis of TEOS accumulated on the CNF surfaces. Scanning transmission electron microscopy indicated that the thickness of silica layer is approximately several nanometers. Pore size distribution analysis for the silica nanolayer suggested the presence of nanopores with 3-5 nm. The TEOS molecules could have accessed the functional groups through the nanopore; therefore, the number of silica nanolayers formed increased with the number of PA coatings. Finally, we compared the PA coating with conventional sol-gel and atomic layer deposition techniques.