Risk Assessment and Potential Analysis of the Agricultural Use of Sewage Sludge in Central Shanxi Province

Abstract

The agricultural use of sewage sludge has become an economic disposal method used worldwide. However, heavy metals contained in sewage sludge have become the crucial limiting factors for this way of disposal. This study showed that regulatory limit values are not enough to determine whether sewage sludge is suitable for agricultural use; risk assessment and potential analysis should be applied. Correlation analysis and hierarchical cluster analysis (HCA) should also be performed to identify heavy metals’ sources and show their influence on sewage sludge utilization. Samples were collected from 13 wastewater treatment plants (WWTPs) located in central Shanxi Province. Results indicated that the mean contents of heavy metals in sewage sludge were all less than the limit threshold of China. According to the monomial potential ecological risk coefficient (), the agricultural use of sewage sludge had low ecological risks for all heavy metals, except for Hg and Cd. Based on the potential ecological risk index (RI), only three stations had moderate risk, other nine stations all had higher potential risk. The mean potentials by all heavy metals were all beyond 10 years, which is the limit of the maximum application time specified by China. Combining all heavy metals, only one station’s potential was less than 10 years. Although the contents of heavy metals were all within the threshold values, large quantities of sewage sludge are not suitable for agricultural use. Coal-related industries, which were the main sources of Hg and Cd, greatly affected the agricultural use of sewage sludge.

Ecological and human health risk assessment of heavy metals in sewage sludge produced in Silesian Voivodeship, Poland: a case study

“…This method is used to assess the ecological risk for a given metal in the various environmental matrices. ER includes both the concentration of a particular metal and its toxicity (Duan & Feng, 2022 ) (Eq. 2 ): where CF — Contamination Factor — the quotient of the concentration of metal in a sample and in the reference or baseline ( B n ) (Håkanson, 1980 ); T is the toxic response factor: Cd = 30, Cr = 2, Cu = 5, Pb = 5, Zn = 1, and Hg = 40.…”

Evaluation of the Heavy Metals Content in Sewage Sludge from Selected Rural and Urban Wastewater Treatment Plants in Poland in Terms of Its Suitability for Agricultural Use

“…The average daily capacity of the treatment plant is 100,000 m 3 /d, the maximum capacity of the treatment plant is 176,500 m 3 /d, approximately 80% of the sewage going to the treatment plant is domestic sewage, 20% of the sewage comes from industry, it is a mechanical-biological sewage treatment plant using the activated sludge method in the sewage treatment process and using the produced biogas, and it receives sewage from the city of Białystok and the areas located in the basin of the Narew and Supraśl rivers, where the following communes are located: Choroszcz, Dobrzyniewo Kościelne, Juchnowiec Kościelny, Supraśl, and Wasilków. The technological line of the sewage treatment plant includes the following facilities and devices: automatic station for receiving delivered sewage; grating hall; screen of screenings with a washer; raw sewage pumping station; two two-chamber sand traps with a separator and sand washer; four primary, oblong settling tanks constituting a set with a predenitrification chamber and a dephosphatation chamber; two pools containing biological reactors with activated sludge; six radial secondary settling tanks; activated sludge pumping station; mechanical activated sludge thickener; separate fermentation chambers; screw press for dewatering excess sludge; and dryer-granulator [27,28].…”

“…Higher contents of heavy metals in municipal sludge will occur in regions with greater industrial development [23]. The content of heavy metals in sediments also varies from country to country due to different national industrial characteristics [24][25][26][27][28]. Also, the permissible upper concentration values of heavy metals in sewage sludge that is intended for natural applications vary from country to country; it is important to note that the use of sludge must comply with all relevant regulations [15].…”

Studying the Effectiveness of Phytoremediation in the Purification of Soils Contaminated with Heavy Metals

“…According to the studies, the excessive growth of cities in recent decades on the one hand, and the lack of sewage collection systems on the other hand have caused agricultural lands to become receivers of municipal sewage and industrial sewage of some industries. Another major issue is the use of sewage sludge in agricultural lands, which contains heavy metals (Iticescu et al, 2021;Duan & Feng, 2022). On the other hand, the use of phosphate fertilizers in agricultural lands causes a decrease in soil pH and the release of lead heavy metals, chromium, cadmium, and arsenic (Atafar et al, 2010;.…”