“Penentuan Kadar Chemical Oxygen Demand (COD) dan Amonia (NH₃) pada Limbah Cair dengan Metode Spektrofotometri UV-Visible

Abstract

Research has been conducted on determining the levels of Chemical Oxygen Demand (COD) and Ammonia (NH₃) in industrial liquid waste in UPT. Laboratory of the Environment Office of North Sumatra Province. Determination of COD levels in closed reflux with the addition of K₂Cr₂O₇ as an oxidizer of organic substances in liquid waste samples and H₂SO₄ as a catalyst, after which the solution is measured using a UV-Visible Spectrophotometer with a wavelength of 420 nm. Determination of Ammonia levels (NH₃) Phenolically with sodium hypochlorite that reacts in ammonia solution to form chloroamine compounds (NH₂Cl) then reacts with phenolic reagents to form quinone monochlorin compounds so that they react with the remaining phenolic reagents to form blue indophenol compounds, after which the solution is measured using a UV-Visible Spectrophotometer with a wavelength of 640 nm. From the measurement results, calculations were then carried out on samples with codes 127 / LC, 133 / LC, and 141 / LC, so that the results for COD levels were obtained, which was 12,369 mg / L; 1,301 mg/L; and 36,304 mg/L; and for NH₃ levels of 3.43485 mg/L; 4.43021 mg/L; and 42.3382 mg / L. Based on the Regulation of the Minister of Environment No. 3 of 2010 concerning wastewater quality standards for industrial areas, liquid waste with sample codes 127 / LC, 133 / LC, and 141 / LC have met cod quality standards with a maximum level of 100 mg / L while liquid waste with sample codes 127 / LC and 133 / LC have met the quality standard requirements NH₃ and liquid waste with sample code 141 / LC is not eligible NH₃ quality standard with a maximum level of 20 mg / L.

Telah dilakukan penelitian penentuan kadar Chemical Oxygen Demand (COD) dan Amonia (NH₃) pada limbah cair industri di UPT. Laboratorium Dinas Lingkungan Hidup Provinsi Sumatera Utara. Penentuan kadar COD secara refluks tertutup dengan penambahan K₂Cr₂O₇ sebagai pengoksidasi zat organik dalam sampel limbah cair dan H₂SO₄ sebagai katalis, setelah itu larutan tersebut diukur menggunakan Spektrofotometer UV-Visible dengan panjang gelombang 420 nm. Penentuan kadar Amonia (NH₃) secara Fenat dengan natrium hipoklorit yang bereaksi dalam larutan amonia membentuk senyawa kloramin (NH₂Cl) kemudian bereaksi dengan reagen fenolat membentuk senyawa monoklor kuinon sehingga bereaksi dengan sisa reagen fenolat membentuk senyawa indofenol berwarna biru, setelah itu larutan tersebut diukur menggunakan Spektrofotometer UV-Visible dengan panjang gelombang 640 nm. Dari hasil pengukuran kemudian dilakukan perhitungan pada sampel dengan kode 127/LC, 133/LC, dan 141/LC, sehingga diperoleh hasil untuk kadar COD yaitu 12,369 mg/L; 1,301 mg/L; dan 36,304 mg/L; dan untuk kadar NH₃ yaitu 3,43485 mg/L; 4,43021 mg/L; dan 42,3382 mg/L. Berdasarkan Peraturan Menteri Lingkungan Hidup RI No 3 Tahun 2010 Tentang baku mutu air limbah bagi kawasan industri, limbah cair dengan kode sampel 127/LC, 133/LC, dan 141/LC telah memenuhi syarat baku mutu COD dengan maksimal kadar sebesar 100 mg/L sedangkan limbah cair dengan kode sampel 127/LC dan 133/LC telah memenuhi syarat baku mutu NH₃ dan limbah cair dengan kode sampel 141/LC tidak memenuhi syarat baku mutu NH₃ dengan kadar maksimal sebesar 20 mg/L.