Autotrophic nitrogen removal over nitrite in a sponge-bed trickling filter

Methods Influence in Surface Area Result from Polyurethane Used as Support Media

We evaluated if different measurement methods influence the surface area results from a polyurethane sponge used as support media in biofilm reactors. The surface area values are normally used to characterize and present advantages from supported medias. However, the methodology to determine it is barely discussed. We compared two specific surface area methodologies: Brunauer-Emmett-Teller (BET) and analysis of images obtained by a scanning electron microscope (SEM). Specific surface area by BET was 93769.1 m2 m-3 (average); for SEM methodology, 10586.6 m2 m-3. The BET value was higher than expected in reality, and the SEM method result was more suitable and used as data input in a mathematical modeling.

Feasibility of packed-bed trickling filters for partial nitritation/anammox: Effects of carrier material, bottom ventilation openings, hydraulic loading rate and free ammonia

This study pioneers the feasibility of cost-effective partial nitritation/anammox (PN/A) in packed-bed trickling filters (TFs). Three parallel TFs tested different carrier materials, the presence or absence of bottom ventilation openings, hydraulic loading rates (HLR, 0.4-2.2 m³ m^-2 h^-1), and free ammonia (FA) levels on synthetic medium. The inexpensive Argex expanded clay was recommended due to the similar nitrogen removal rates as commercially used plastics. Top-only ventilation at an optimum HLR of 1.8 m³ m^-2 h^-1 could remove approximately 60% of the total nitrogen load (i.e., 300 mg N L^-1 d^-1, 30 °C) and achieve relatively low NO₃^--N accumulation (13%). Likely FA levels of around 1.3-3.2 mg N L^-1 suppressed nitratation. Most of the total nitrogen removal took place in the upper third of the reactor, where anammox activity was highest. Provided further optimizations, the results demonstrated TFs are suitable for low-energy shortcut nitrogen removal.

Seeding the drainage canal of a wastewater treatment system for the natural rubber industry with rubber for the enhanced removal of organic matter and nitrogen

Current pretreatment methods for wastewater from natural rubber (NR) factories either have low rubber recovery efficiency or are costly to operate. A wastewater treatment system was developed that combines a pretreatment canal (PTC) seeded with rubber, an anaerobic baffled reactor (ABR), and a down-flow hanging sponge (DHS) reactor. The PTC is simple to implement and contributes to not only rubber recovery but also organic matter removal in the ABR and nitrogen removal in the DHS reactor. In experiments, the PTC recovered 16.6% of residual rubber through coagulation. The ABR increased the chemical oxygen demand removal efficiency and methane recovery compared with other anaerobic reactors treating raw NR wastewater. The DHS reactor removed 30.7% of total inorganic nitrogen (TIN) by nitrification, anaerobic ammonia oxidation and denitrification. Feeding the bottom stage of the DHS reactor with sodium acetate solution increased the TIN removal efficiency to 87.8%. The water quality of the final effluent achieved the Vietnamese standards for the NR industry. Microbial community analysis was performed to identify the dominant microorganisms and mechanisms in the PTC, ABR, and DHS reactor.

Development of a single-stage mainstream anammox process using a sponge-bed trickling filter

Anaerobic ammonia oxidation to nitrogen gas using nitrite as the electron acceptor (anammox process) is considered a cost-effective solution for nitrogen removal after an anaerobic pre-treatment process. In this study, we conducted a laboratory-scale experiment to develop a single-stage partial nitritation-anammox process in a sponge-based trickling filter (STF) reactor, inoculated with anammox sludge, simulating the treatment of anaerobically pretreated concentrated domestic sewage without mechanical oxygen control. The influent ammonia concentration was 100 mg-N·L^-1. The K_La of the STF reactor was higher than those observed for conventional activated sludge processes. The STF reactor performed at 89.8 ± 8.2% and 42.7 ± 16.9% ammonia and TN removal efficiency, respectively, with a nitrogen loading rate of 0.55 ± 0.20 kg-N·m^-3·day^-1 calculated based on sponge volume. Microbial community analysis of the STF-retained sludge indicated that both autotrophic and heterotrophic nitrogen removal occurred in the reactor.

The effect and biological mechanism of granular sludge size on performance of autotrophic nitrogen removal system

The autotrophic process for nitrogen removal has attracted worldwide attention in the field of wastewater treatment, and the performance of this process is greatly influenced by the size of granular sludge particles present in the system. In this work, the granular sludge was divided into three groups, i.e. large size (> 1.2 mm), medium size (0.6-1.2 mm) and small size (< 0.6 mm). The medium granular sludge was observed to dominate at high volumetric nitrogen loading rates, while offering strong support for good performance. Its indispensable contribution was found to originate from improved settling velocity (0.84 ± 0.10 cm/s), high SOUR-A (specific oxygen uptake rate for ammonia oxidizing bacteria, 25.93 mg O₂/g MLVSS/h), low SOUR-N (specific oxygen uptake rate for nitrite oxidizing bacteria, 3.39 mg O₂/g MLVSS/h), and a reasonable microbial spatial distribution.