Sustainable Utilization of Sewage Sludge through the Synthesis of Liquid Fertilizer

Yan-Jhang Chen,Sandhya Babel,Li-Pang Wang

doi:10.3390/su14010387

Yan-Jhang Chen, Sandhya Babel + Show 1 more

Open Access

https://doi.org/10.3390/su14010387

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Abstract

In a world with a growing human population, resources are becoming increasingly scarce. To ensure food supply, fertilizers are often used to accelerate growth when planting agricultural products. Sewage sludge (SS), containing as high as 10–15 wt% Phosphorus (P), can be synthesized into liquid fertilizer. P species in SS can generally be classified into four types: inorganic phosphorus (IP), organic phosphorus (OP), nonapatite inorganic phosphorus (NAIP), and apatite phosphorus (AP). However, OP is not leached out by wet chemical methods and NAIP is not bioavailable. This study investigated the P-form conversion (OP and NAIP to AP) in SS by adding 8 wt% CaO at 300 °C. SS through pretreatment can easily leach out P when combined with organic acid. The content of heavy metals is in accordance with fertilizer regulations in a leaching solution. The solution was mixed with potassium and ammonia compounds to synthesize a liquid fertilizer. To ensure the safe and efficient use of liquid fertilizer and undertake an analysis of heavy metals, an aquatic organisms (D. magna) toxicity test, and the growth of plants test were both used. The liquid fertilizer can be demonstrated to accelerate the growth of plants while not causing the death of D. magna in short time, as the liquid fertilizer has enough nutrients to help the D. magna to survive.

Highlights

In a world with a growing human population, resources are becoming increasingly scarce [1]
At 300 the fraction of organic phosphorus (OP) decreased to 0%, that of nonapatite inorganic phosphorus (NAIP) decreased
The results suggest that when 8 wt% CaO was added at 300 ◦ C for 2 h, the OP was converted to apatite phosphorus (AP), which enhanced recovery of P because the AP was leached out by inorganic and organic acid [42]

Summary

Introduction

In a world with a growing human population, resources are becoming increasingly scarce [1]. In order to ensure food supply, fertilizers are often used to accelerate growth when planting agricultural products. The millions of tons of sewage sludge (SS) generated globally each day is causing waste management problems [2]. The daily SS production in Taiwan is approximately 68,000 tons [3]. P content in SS may be as high as 10–15 wt% [4]. Because of advancements in wastewater treatment technologies, the P content in SS has increased [5]

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