Evaluation of phosphorus removal from wastewater by soils in rural areas in China

Abstract

Low-cost, easy-maintenance and high-efficiency decentralized wastewater treatment technologies are urgently needed in rural areas of China. Processes with high potential for phosphorus removal are of great interest. However, commonly used treatment methods often do not meet the strict criteria for removing phosphorus from rural wastewater. In order to search an economic and simple technology for phosphorus removal from the common bio-technologies effluent, seven soil types collected from different rural areas in China were investigated for their ability to remove phosphorus. X-ray diffraction (XRD) was used to analyse the mineral structure, and inductively coupled plasma optical emission spectrometer (ICP-OES) was used to analyse the geochemical composition of the soil samples. Three primary minerals -quartz, albite and montmorillonite -were clearly detected. The samples were divided into two soil types, acidic soils and alkaline soils, based on their pH values. The geochemical composition study indicated that a higher percentage of Ca and Mg occurred in alkaline soils (pH > 8) than in acidic soils (pH < 6.5). Adsorption isotherms from batch experiments fitted the Langmuir and Freundlich models well, the maximum P adsorption capacities ranged from 0.256 to 1.598 mg P/g, indicating a high phosphorus removal potential for all of these soils. The P fractions extracted revealed that the sum of NaOH-extracted inorganic P (NaOH-Pi) was the major P component in the acidic soils, and CaCO 3 -bound phosphorus (Ca-P) in the alkaline soils. Dynamic adsorption simulation showed that these soils have the ability to remove phosphorus from wastewater.

Changes in chemical attributes of a Fluvent cultivated with castor bean and irrigated with wastewater

“…Liang et al (2010) found that soil from rural areas of China with mineralogy similar to Fluvic Neosol (with high amount of kaolinite) showed high P content in wastewater due to the low adsorption capacity of the soil.…”

“…The magnitude of changes in soil chemical attributes depends mainly on local conditions, such as soil type, depth range, quality and quantity of used wastewaster in the system, and the kind of grown plant species (Corwin & Bradford, 2008;Kiziloglu et al, 2008;Xu et al, 2010;Liang et al, 2010;Leal et al, 2010). These changes may result in significant impacts in the soil quality (Fonseca et al, 2005;Herpin et al, 2007), or may not (Varallo et al, 2010;Duan et al, 2010).…”

Multi-Soil-Layering Systems for Wastewater Treatment in Small and Remote Communities

“…For example, many individual residences in rural areas rely on septic tanks to dispose of their wastewater. Although septic tanks are an easy and safe technique, the concentration of suspended solids (SS), biochemical oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP) in effluents from septic tanks can hardly meet the discharge requirements (Liang et al, 2010). It is also noted that septic tanks are not correctly designed, built and operated in many situations.…”

Tower bio-vermifilter system for rural wastewater treatment: bench-scale, pilot-scale, and engineering applications

“…Decentralized wastewater treatment has been explored as an alternative for reducing pollutant load from rural regions, which ideally could cater the special needs of rural sewage treatment such as tolerance of variable pollutant loads, stable and high removal efficiencies of nutrients and organic compounds, and low construction and operation costs. There are mainly two types of decentralized wastewater treatment technologies for rural sewage treatment: (1) activated sludge process such as packed bed biofilm reactor (Liang et al (2010a)), cyclic activated sludge system (CASS) ), and anaerobic sludge reactor; (2) land treatment process such as stabilization pond (Verbyla et al (2013)), constructed wetland (Li et al (2009), Wu et al (2011), and soil infiltration system (Liang et al (2010b)). …”