Effectiveness of agricultural waste in the enhancement of biological denitrification of aquaculture wastewater

Abstract

Nitrogen pollution in aquaculture wastewater can pose a significant health and environmental risk if not removed before wastewater is discharged. Biological denitrification uses external carbon sources to remove nitrogen from wastewater; however, these carbon sources are often expensive and require significant energy. In this study, we investigated how six types of agricultural waste can be used as solid carbon sources in biological denitrification. Banana stalk (BS), loofah sponge (LS), sorghum stalk (SS), sweet potato stalk (SPS), watermelon skins (WS) and wheat husk (WH) were studied to determine their capacity to release carbon and improve denitrification efficiency. The results of batch experiments showed that all six agricultural wastes had excellent carbon release capacities, with cumulative chemical oxygen demands of 37.74–535.68 mg/g. During the 168-h reaction, the carbon release process followed the second-order kinetic equation and Ritger-Peppas equation, while carbon release occurred via diffusion. The kinetic equation fitting, scanning electron microscopy, and Fourier transform infrared spectroscopy results showed that LS had the lowest cm and the maximum t1/2 values and only suffered a moderate degree of hydrolysis. It also had the lowest pollutant release rate and cumulative chemical oxygen demand, as well as the most efficient removal of total phosphorous (TP) and total nitrogen (TN). Therefore, we concluded that LS has the lowest potential risk of excess carbon release and capacity for long-lasting and stable carbon release. The WS leachate had the highest TN contents, while the SPS leachate had the highest TP content. In the 181-h denitrification reaction, all six agricultural wastes completely removed nitrate and nitrite; however, SS had the highest denitrification rate, followed by LS, WH, BS, SPS, and WS (2.16, 1.35, 1.35, 1.34, 1.34, and 1.01 mg/(L·h), respectively). The denitrification process followed a zero-order and first-order kinetic equation. These results provide theoretical guidance for effectively selecting agricultural waste as a solid carbon source and improving the denitrification efficiency of aquaculture wastewater treatment.

Comparative investigation on heterotrophic denitrification driven by different biodegradable polymers for nitrate removal in mariculture wastewater: Organic carbon release, denitrification performance, and microbial community

“…The pore structure and pore size of RS and CC increased significantly after carbon source release ( Figures 4A , B ). Gao et al (2022) also observed the same phenomenon. This change is caused by the fact that agricultural waste contains crude fiber or lignin, which makes it difficult to degrade, and provides more pore structure with soluble substances, which may also be the reason for the large amount of carbon released from agricultural waste.…”

Effects of hydraulic retention time and influent nitrate concentration on solid-phase denitrification system using wheat husk as carbon source

“…When the HRT was increased to 28, 32, and 36 h, the ENC of WH-DR decreased, the inhibition of NO 2 − -N reductase was weakened, and NO 2 − -N was completely removed as nitrogen. Adding plant carbon sources may increase the risk of secondary pollution, such as nitrogen release and incomplete nitrogen removal ( Gao et al, 2022 ); However, in this study, the removal process of TN and NO 3 − -N showed a similar pattern ( Fig. 2 ).…”

“…Data were collected as previously described in Zhang et al (2020) and Tu et al (2010) . More details on these methods have been described in our previous study ( Gao et al, 2022 ). Specifically, NH 4 + -N concentrations were measured using the spectrophotometric method with salicylic acid.…”

“…Previous studies have focused on WH for the development of bio-based materials ( Barbieri, Lassinantti Gualtieri & Siligardi, 2020 ) and its ability to act as a biosorption medium for efficient adsorption of 2,4-dichlorophenol from aqueous solution ( Kalderis et al, 2017 ). Our previous research has shown that WH exhibits excellent carbon release capacity and completely removed nitrate and nitrite during a 181-h denitrification reaction ( Gao et al, 2022 ). However, less information was revealed on the effects of HRT and INC on solid-phase denitrification system using WH as carbon source in aquaculture wastewater treatment.…”

Systematic review: External carbon source for biological denitrification for wastewater

“…By-products from alcohol production in terms of their potential application as external carbon can be the best option (Czerwionka et al, 2012). External carbon source from several types of waste such as use of external carbon sources derived from biowaste (Katsou et al, 2014), food waste (X.-C. Feng et al, 2021), agricultural waste (S. Gao et al, 2022) and other types of waste can be utilized for this purpose. Thus, after reviewing several studies around the globe, it has been concluded that denitrification and addition of suitable carbon source are best combination for wastewater treatment.…”