Synthesis of Layered Double Hydroxides with Fermentation Liquid of Organic Waste To Extract Short-Chain Fatty Acids as a Biodenitrification Carbon Source

Abstract

Short-chain fatty acids (SCFAs) were extracted from artificial and actual anaerobic fermentation liquid of organic waste via the synthesis of layered double hydroxides (LDHs), which was then used as external carbon source in biodenitrification process. Results of X-ray diffraction and Fourier transform infrared analysis indicate that SCFAs were successfully intercalated into LDHs in both artificial system and actual anaerobic fermentation liquid of food waste, with good slow release performance. When using SCFAs-LDH and SCFAs-Na as carbon source with COD/N ratio of 4:1, the nitrate removal efficiency and the utilization efficiency of carbon source were improved from 42.3% and 30.3% to 81.3% and 58.1%, respectively. A dynamic “release-utilization” balance of carbon source was always kept during denitrification process when using SCFAs-LDH, so that higher removal efficiency of nitrate and utilization efficiency of carbon source were obtained simultaneously. This study could help to recover SCFAs from organic wastes efficiently as a denitrification carbon source with slow release performance.

Pretreating anaerobic fermentation liquid with calcium addition to improve short chain fatty acids extraction via in situ synthesis of layered double hydroxides

“…The SCFAs-LDH and sodium acetate and the corresponding total nitrogen removal efficiency were investigated by previous study (Jiang et al, 2017). The results show that the cost of using SCFAs-LDH was about 1.15 RMB/m 3 wastewater, which was much higher than that of using sodium acetate (about 0.29 RMB/m 3 wastewater.…”

“…But the useful FA would not be consumed and need to be further recovered in the sludge treatment process (to be separated) or removed in the mainstream wastewater treatment process (to increase the nitrogen load of the mainstream), from the view of mass balance (Huang et al, 2016). Layered double hydroxides (LDHs), as a class of synthetic clay mineral (Clark et al, produced SCFAs-LDH serving as slow release carbon source (free from ammonia) for bio denitrification (Jiang et al, 2017). It was also found that, there was a certain amount of carbonate in the synthesized sample.…”

Innovative Integrated Technique for Nutrient Acquisition: Simultaneous Recovery of Carbon and Nitrogen Sources from the Anaerobic Fermentation Liquid of Food Waste

“…Recovery of C was realized via the synthesis of VFA-LDH, which was prepared with anaerobic fermentation liquid from food waste via coprecipitation under a controlled pH. The experimental procedure was carried out based on refs and with some modifications, and the details were as follows: Fermentation liquid (5.0 L) was placed in the automatic control reactor, and the pH was adjusted to the expected pH (∼9.5) with 4 M NaOH or 4 M HCl. Then, 0.30 mol of Mg 2+ solution (150 mL) and 0.15 mol of Al 3+ solution (150 mL) were added to the reactor dropwise under constant agitation (100 rpm) in an N 2 atmosphere.…”

“…Extracting VFAs and NH 3 –N from anaerobic fermentation liquid could solve these problems simultaneously. Layered double hydroxide (LDH), known as hydrotalcite-like compounds or anionic clays, are a family of compounds which commonly adopt the general formula M 1– x 2+ M x 3+ (OH) 2 (A n– ) x / n · m H 2 O (where M 2+ and M 3+ are metal cations, and A n– is an interlayer anion). , The isomorphic substitution of M 2+ by M 3+ results in a high charge density of the layers, which should be balanced by exchangeable interlayer anions. , Researches have shown that LDH has been prepared successfully with various targets, such as agrochemicals and phosphate and nitrate ions, as well as volatile organic acids . Such studies have suggested the feasibility of extracting VFAs from anaerobic fermentation liquid via LDH synthesis.…”

“…Meanwhile, to address high concentrations of NH 3 –N in anaerobic fermentation liquid, efforts have been made to recycle and reuse N, for example via the gas-stripping method for NH 3 –N recovery. − Generally, NH 3 –N recovery efficiency is greatly affected by pH and temperature when using the gas-stripping method. , During LDH synthesis, two essential conditions, a fermentation liquid pH of ∼9.5 and temperature of ∼70 °C are ideally required for gas-stripping. Such a method could simultaneously recover C and N from anaerobic fermentation liquid, which could be reused to improve soil fertility and enhance plant growth. , Furthermore, the combination of LDH synthesis and gas-stripping for C and N extraction could decrease the effects of organic pollutants on the environment.…”