Abstract
Recycling and reusing the nutrient resources from anaerobic digested slurry is very promising for environmental pollution control and agriculture sustainable development. We focus here on nitrogen and phosphorus recycling in treating cattle manure anaerobic digested slurry by a magnesium ammonium phosphate (struvite-MAP) crystallization process and examine the impact of MAP precipitation on plant growth. The MAP crystallization process was studied by a combination of Design-Expert 8.0.6 software, mathematical modeling, and experiments. The influence of Mg/P, N/P and pH on nitrogen (N) and phosphorus (P) recovery was investigated. Then, the fertilizing efficiency of the MAP precipitate on the growth of three vegetables (water spinach (Swamp cabbage), amaranth and Brassica parachinensis) was also evaluated. The results showed that more than 89% of N and 99% of P could be recovered at pH = 10 with molar ratios of Mg/P = 1.6 and N/P = 1.2. Compared with the control pots and potassium chloridepots, the fresh weight, dry weight and average height of swamp cabbage in the MAP pots were obviously enhanced without burning effects. The results showed that MAP precipitation can promote the development of plants, which is promising for its use as a slow-release fertilizer for agricultural production.
Highlights
In recent years, biogas projects have been widely used to treat the manure and sewage of poultry and livestock
Compared with the control pots and potassium chloridepots, the fresh weight, dry weight and average height of swamp cabbage in the magnesium ammonium ammonium phosphate (MAP) pots were obviously enhanced without burning effects
The results showed that MAP precipitation can promote the development of plants, which is promising for its use as a slow-release fertilizer for agricultural production
Summary
Biogas projects have been widely used to treat the manure and sewage of poultry and livestock. These projects achieve concentrated waste treatment and resource reuse, which is beneficial for environmental protection, energy saving and economic growth [1]. Due to the limitations of technology, management, and operational costs, biogas slurry is produced after anaerobic fermentation and this is a serious threat to the ecological environment and a major restriction to the development of biogas project as well [2,3]. High concentrations of nutrient elements such as nitrogen (N) and phosphorus (P) in the biogas sludge make the biogas slurry valuable for reuse. Phosphorus, a valuable resource which is non-renewable and has limited availability in nature, has the potential to cause eutrophication or blue green algal blooms in receiving waters [4,5].
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