Fast treatment and recycling method of large-scale vegetable wastes

Abstract

With rapid development of vegetable industry in China, in process of refrigerated transportation and storage, large-scale abandoned vegetable wastes (VW) need to be urgently treated alone since they rot very fast and would pollute the environment seriously. Existing treatment projects generally regard VW as garbage with high content of water and adopt the process of squeeze and sewage treatment, which leads to not only high treatment costs but also great resource waste. Therefore, according to the composition and degradation characteristics of VW, a novel fast treatment and recycling method of VW was proposed in this paper. VW are first degraded with thermostatic anaerobic digestion (AD) and then the residues decompose rapidly with thermostatic aerobic digestion to meet the farmland application standard. To verify the feasibility of the method, the pressed VW water (PVW) and VW from the VW treatment plant were mixed and degraded in two 0.56 m³ digesters, and degraded substances were continuously measured in 30 days' mesophilic AD at 37 ± 1 °C. Subsequently, the biogas slurry (BS) produced by AD is decomposed by thermostatic aerobic aeration decomposition at 30 °C for 48 h to rapidly decompose. BS was confirmed to use safely for plants by germination index (GI) test. The results show that 96 % chemical oxygen demand (COD) from 15,711 mg/L to 1000 mg/L within 31 days and the GI of treated BS was 81.75 %. Besides, nutrient elements of N, P, and K keep good abundance, no heavy metals, pesticide residue, and hazardous substances were found. Other parameters were all lower than the BS placed for a half-year. VW are fast-treated and recycled with the new method, which provides a novel method for fast treatment and recycling of large-scale VW.

Keywords: Aerobic treatment; Anaerobic digestion; Fast treatment method; Large-scale waste vegetable treatment and recycling; Removal efficiency.