การจัดการน้ำเสียที่ผ่านการบำบัดจากโรงงานสกัดน้ำมันปาล์มดิบด้วยการปลูกหญ้าเนเปียร์

Abstract

This research is aimed at determining the reduction of color, organic matter, and phenolic compounds in treated palm oil mill effluent (POME) by land treatment in soil column (S) and soil column with plantation of Napier grass (SG). The treated POME was daily applied to soil columns. Three applied rates including 5 (column S5 and SG5), 7 (column S7 and SG7), 10 cm/weeks (column S10 and SG10) and standard Napier grass plantation rate of 10 cm/week (column SPG) were used to conduct the experiment for 16 weeks. Duplicated experiments were conducted for each applied rate. Average values of pH, color, chemical oxygen demand (COD), total kjeldah nitrogen (KN), total organic carbon (TOC) and phenolic compounds were 8.6, 1,656 PtCo, 1,443 mg/L, 445 mg/L, 324 mg/l and 134 mg GAEL, respectively. pH of treated water gradually increased from slightly acidic condition to neutral condition between 5.9 and 7.3. Color of treated water decreased gradually. At 16 weeks, column S7 had the highest percent reduction of color of 99.5%. Highest percent reductions of COD, TKN, and TOC of 95.6, 94.8, and 95.596 were obtained using column S5, SG7, and S10, respectively. The percent reduction of phenolic compounds between 94.6-96.7% was determined. Highest values of first order degradation rate constant of COD and phenolic compounds of column SGS were 2.081 and 2472 day', respectively. pH of soil increased from slightly acidic condition to neutral condition. The percent of total nitrogen, zinc, organic matter and cation exchange capacity slightly changed in soil. The available phosphorus and potassium increased from 26.8 to 31.1-43.6 mg/kg and 59.8 to 218-330 mg/kg, respectively. Total phenolic compounds increased from 60 to 83-133 mg/kg. The soil sample in column SG7 had the highest amount of degradable phenolic compounds at 12.8 $ 1.5 log MPN/1 g soil. The dominant group of bacteria that can degrade phenolic compounds was Rhodococcus sp. When considering the column with Napier grass plantation in terms of efficiency, growth, and quality of Napier grass, the best condition was determined at the applied rate of 7 cm/week (SG7). For column without Napier plantation, the best condition was determined at the applied rate of 7 cm/week (S7). Treated water quality with one stage soil column with plantation of Napier grass could not meet industrial effluent standards. The two stage of land treatment was proposed. In the first stage, the treated POME was applied to the soil with plantation of Napier grass. The high density polyethylene liner was used for collecting the treated water and protection of groundwater contamination. The treated water from stage one was feed to land treatment without Napier grass plantation or oil palm garden in stage two. The final treated water can be used in processing or discharging to natural water sources. Napier grass planted with treated wastewater had nutritional value similar to standard planting and could be sold as animal feed and as raw material of biogas.