Abstract
The intensification of pig production is considered a risky activity for the environment when the generated pig slurry is not adequately treated. In addition, intensive agriculture practices where pig slurry is applied to the cropland could cause nitrate leaching, salinization, and soil pollution (heavy metals and pathogens), thus the development of an eco-friendly system for pig slurry treatment is essential to avoid undesirable environmental impacts. The main objective of this study was to assess the efficiency of an integrated purification system (IPS) for treating pig slurry. The system included a pretreatment module (raw pig slurry tank, phase separator, aeration tank, and settlement tank), constructed wetlands (CWs) that included an unplanted cell and a planted cell, and a storage pond (SP). Pig slurry samples from the pretreatment modules, CWs, and SP were collected in triplicate and physic-chemical and microbial analyses were performed. Results showed that the pretreatment modules decreased the total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) concentrations in the liquid fraction. Higher total nitrogen removal was reported in the planted cell, which decreased from 4.0 g L−1 to 1.9 g L−1 in the inflow and outflow, respectively. Total efficiencies over 85% were found in the planted and unplanted cells for TSS, Kjeldahl nitrogen (KN), chemical oxygen demand (COD), and TP. Microbial parameters were eliminated after the treatment in the planted cell. Therefore, the results indicated that filtration (pretreatment), purification (constructed wetland), and bioremediation (storage pond) constituted an appropriate IPS for treating pig slurry.
Highlights
The intensification of pig production is considered a risky activity for the environment when the generated pig slurry is not adequately treated [1]
The main problems caused by pig slurry (PS) application on agricultural soils are related to eutrophication and acidification on water bodies, nitrate leaching and greenhouse gas emissions [3,4]
Results showed that total suspended solids (TSS) was reduced by 35% with the mechanical separation, previous studies have indicated that a mechanical pretreatment previous the use of horizontal subsurface flow constructed wetland (HSFCW) avoid clogging of the wetlands and lengthens the life of the system [32]
Summary
The intensification of pig production is considered a risky activity for the environment when the generated pig slurry is not adequately treated [1]. The intensive agricultural activities implicate the overuse of fertilizers (mineral and organic), which could cause nitrate leaching, salinization, and soil pollution (heavy metals and pathogens), the development of an eco-friendly system for pig slurry treatment is essential to avoid undesirable environmental impacts [2]. Pig slurry is an important source of trace metals and pathogens. Trace metals, such as Cu, Zn, and Cd, are used worldwide in intensive animal breeding for preventing infectious diseases and as growth promoters [5], these heavy metals can be accumulated in the soil, uptake by plants and affect the health of animals and people through the food chain. Pig slurry is characterized by a high level of Agronomy 2020, 10, 208; doi:10.3390/agronomy10020208 www.mdpi.com/journal/agronomy
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