Effect of Chitosan Concentration and Dosage in Sequential Biosurfactant-Chitosan Treatment of Produced Water

Abstract

Produced water from oil and gas production contains high oil and grease (O&G), Chemical Oxygen Demand (COD), and ammonia, requiring treatment before discharge. This study determined optimum chitosan concentration and dosage for sequential biosurfactant-chitosan treatment, modeled the dosage-concentration interaction using Response Surface Methodology (RSM), and examined the adsorption mechanism via nonlinear isotherms. Highest individual removals were 90% O&G (2.5% dosage, 1% concentration), 52.4% ammonia (4.5%, 1%), and 25.4% COD (1.5%, 0.5%). Canonical analysis confirmed a true maximum for O&G (68.50% predicted at 2.930%, 0.657%), while the COD model was a saddle surface whose stationary point fell outside the tested range (0.5%, 0.1%; 38.6% predicted), and the ammonia model was not significant due to low R² value. RSM optimization gave a compromise condition (1.26%, 0.99%) but only 0.40 desirability, reflecting O&G-COD antagonism. Isotherm analysis showed O&G and COD removal were driven mainly by coagulation-flocculation rather than true adsorption. These results support OPEFB biosurfactant and shrimp-shell chitosan as a sustainable pre-treatment for produced water.

Air terproduksi dari industri minyak dan gas mengandung minyak dan lemak (O&G), Chemical Oxygen Demand (COD), dan amonia dalam konsentrasi tinggi sehingga memerlukan pengolahan sebelum dibuang. Penelitian ini menentukan konsentrasi dan dosis kitosan optimum untuk pengolahan sekuensial biosurfaktan-kitosan, memodelkan interaksi dosis-konsentrasi menggunakan Response Surface Methodology (RSM), dan mengkaji mekanisme adsorpsi melalui isoterm nonlinear. Penyisihan individual tertinggi adalah 90% O&G (dosis 2,5%, konsentrasi 1%), 52,4% amonia (4,5%, 1%), dan 25,4% COD (1,5%, 0,5%). Analisis kanonik mengonfirmasi titik maksimum O&G (prediksi 68,50% pada dosis 2,930%, konsentrasi 0,657%), sedangkan titik maksimum model COD berada di luar rentang uji (0,5%, 0,1%; prediksi 38,6%). Model amonia tidak signifikan karena nilai R² yang rendah. Optimasi RSM menghasilkan kondisi kompromi (dosis 1,26%, konsentrasi 0,99%) namun hanya memiliki desirability sebesar 0,40 akibat antagonisme O&G-COD. Analisis isoterm menunjukkan bahwa penyisihan O&G dan COD didominasi oleh mekanisme koagulasi-flokulasi, bukan adsorpsi sejati. Hasil ini mendukung biosurfaktan TKKS dan kitosan kulit udang sebagai pendekatan pra-pengolahan berkelanjutan untuk air terproduksi.