Approaches to the mitigation of ammonia inhibition during anaerobic digestion – a review

Abstract

The digestion process of organic waste rich in high ammonia content has always been a gridlock during the methanogenesis process. The free ammonia may increase inhibition/toxicity, which in turn affects the microbial community in the digester and eventually leads to process failures. Substantial methods have been proposed and assessed for curtailing ammonia emissions in anaerobic digesters to attain a safe and steady process so that, along with high methane production, high quality effluents can also be recovered. There are several means for lowering the erratic ammonia in organic wastes that are in use currently, such as decrease of pH, which favours the formation of ammonium over ammonia in the equilibrium; for example, the use of chemical additives that attach ammonium-N. Ammonia can also be removed from nitrogen-rich substrates during anaerobic digestion through other methods such as struvite precipitation, membrane distillation, air stripping, ion exchange, and adsorption. A thorough survey of different articles has shown that ion exchange, adsorption and changing of the C/N ratio through the co-digestion technique are the most commonly studied methods for mitigating ammonia inhibition in wastewater during anaerobic digestion. A detailed review of these methods in the context of nitrogen-rich substrates will be discussed in this paper.

Approaches to mitigation of hydrogen sulfide during anaerobic digestion process – A review

“… High surface area of the adsorbent (500 m 2 /g) Chemically activated adsorbent Optimal calcination temperature of 800 °C Pretreatment methods Nitrogen, oxygen, and sulfur functional groups integrated with the carbon structure [ 129 , 130 , 131 ] Stripping A physical system in which air and wastewater flow in opposite directions under mass transfer. High operating temperature (above 45 °C) Stripping tower for volatilization of H 2 S [ 132 , 133 ] Wet scrubbing The method uses water as an adsorbent since H 2 S is more soluble in water than methane. Higher Ultra Violet (UV) light intensity of about 132 μW/cm 2 Solution pH of 7.61 Gas flow rate is about 1.5 L/min H 2 O 2 concentration of 0.2 mol/L Low temperature (10 °C) Clean air with little traces of H 2 S is discharged from the reactor and can be discharged into the atmosphere [ 134 , 135 ] Aerobic biological technology The process involves using a low concentration of (DO) for microorganisms to facilitate hydrolysis acidification.…”

Biofuel Recovery from Plantain and Banana Plant Wastes: Integration of Biochemical and Thermochemical Approach

“…In AD, Total Ammonium Nitrate (TAN) not greater than 200 mg/L was observed to be conducive and acceptable [121]. Most of the studies described some techniques for ammonia reduction, such as co-digestion by changing the C/N ratio, exchange of ions, air stripping, and adsorption, and also pH monitoring in the range of 6.5 (±0.5) was observed as a suitable method, promoting sustainability, stability, and the increase of CH 4 production [122]. The AD process for bioenergy production uses a variety of feedstocks, including animal and agricultural biomass.…”

Anaerobic digestion and recycling of kitchen waste: a review

“…Ammonia inhibition is a major factor influencing anaerobic digestion treatment of kitchen waste because a high concentration of total ammonia nitrogen (TAN) is generated during the digestion process (Li et al 2018a). Free ammonia nitrogen (NH 3 -N, FAN) and ionized ammonia (NH 4 + -N) are the two forms of reduced inorganic nitrogen that exist in equilibrium depending upon the pH and temperature of the aqueous phase (Mutegoa et al 2020). Free ammonia nitrogen is considered to be the main contributor to ammonia inhibition (Tian et al 2018).…”