COD and Phosphate Distribution Analysis from Domestic and Agricultural Activities Along Irrigation Channel in Metro City, Lampung, Indonesia

Abstract

Abstrak

Kualitas air irigasi memiliki peran penting dalam mendukung ketahanan pangan, keberlanjutan ekosistem, dan kesehatan masyarakat. Kecamatan Metro Pusat di Kota Metro, Lampung, sebagai wilayah yang bergantung pada sistem irigasi pertanian, rentan terhadap pencemaran dari sumber domestik dan non-domestik. Penelitian ini bertujuan menganalisis konsentrasi Chemical Oxygen Demand (COD) dan fosfat pada saluran irigasi serta memprediksi distribusi polutan di bagian hilir yang berasal dari aktivitas rumah tangga dan pertanian. Pengambilan sampel dilakukan pada empat titik Non-Point Source (NPS) dan tiga titik Point Source (PS). Hasil penelitian menunjukkan bahwa seluruh nilai COD melebihi baku mutu Kelas II berdasarkan Peraturan Pemerintah Nomor 22 Tahun 2021. Konsentrasi tertinggi ditemukan pada PS1 sebesar 285 mgL^-1, sedangkan konsentrasi fosfat tertinggi terdapat pada PS2 sebesar 4,34 mgL^-1, yang dipengaruhi oleh pembuangan deterjen dan limbah organik domestik. Dengan menggunakan metode neraca massa melalui pemodelan analitik, diprediksi adanya penurunan konsentrasi polutan di sepanjang aliran irigasi akibat proses sedimentasi dan degradasi alami. Konsentrasi COD menurun dari 104,93 mgL^-1pada segmen 1 (CR1) menjadi 89,63 mgL^-1 pada segmen 2 (CR2) dan 50 mgL^-1 pada segmen 3 (CR3). Konsentrasi ortofosfat menunjukkan pola serupa, yaitu penurunan dari 0,06512 mgL^-1 (CR1) menjadi 0,06510 mgL^-1 (CR2) dan 0,06481 mgL^-1 (CR3). Oleh karena itu, pengendalian beban pencemaran, terutama di bagian hulu, sangat penting untuk menjaga keberlanjutan kualitas air. Hasil penelitian ini dapat menjadi rujukan bagi pemerintah daerah dalam merumuskan strategi pengelolaan sumber daya air yang berkelanjutan.

Abstract

Irrigation water quality is of major importance for public health, environmental sustainability and food security. Located in the heavy agricultural irrigation systems, the Central Metro District in Lampung, Metro City, is vulnerable to contamination from domestic and external sources. The objective of this study is to determine the concentration of phosphate and COD (Chemical Oxygen Demand) in the district irrigation channel and to predict the spread of pollutants downstream due to residential and agricultural activities. The study was conducted at three Point Source (PS) and four Non-Point Source (NPS) sites. The results showed that all COD measurements exceeded the water quality limits of Class II based on Government Regulation No. 22 of 2021. The highest COD content (285 mgL-1) was recorded in PS1 and the highest phosphate concentration (4.34 mgL^-1) in PS2. Both were affected by the discharge of domestic organic waste from residential areas and detergents. The study used analytical modelling and a mass balance approach to estimate a slow decrease in pollutant concentrations downstream as a result of natural sedimentation and degradation processes. COD levels decreased from 104.93 mgL^-1 in segment 1 or combined concentration NPS 1 (CR1) to 89.63 mgL^-1 in segment 2 (CR2) and 50 mgL^-1 in segment 3 (CR3). Orthophosphate concentrations exhibited a similar pattern, decreasing from 0.06512 mgL^-1 (CR1) to 0.06510 mgL^-1 (CR2) and 0.06481 mgL^-1 (CR3). Therefore, lowering the total pollutant load in the irrigation system requires upstream pollution control. It is anticipated that the results of this study will assist local governments in developing sustainable plans for managing water resources.