Assessment of groundwater contaminant loading potential for Yogyakarta urban area

PHONHALATH, Keophousone, Dr.Ir. Heru Hendrayana

2007 | Tesis | S2 Teknik Geologi

Kebutuhan air minum dan penggunaan air untuk kebutuhan sehari-hari di kota Yogyakarta sebagian besar dari sumur gali penduduk (air tanah) dan PDAM. Pertambahan penduduk dan aktifitasnya akan mengakibatkan turunnya kualitas dari air tanah. Sumber-sumber pencemar yang dapat mengakibatkan degradasi air tanah dapat berasal dari limbah rumah tangga, SPBU, limbah dari industri batik dan pertanian. Hal pokok yang dibahas dalam pencemaran adalah mengidentifikasi sumber pencemar, mengidentifikasi kemunculan sumber pencemar, mengetahui kondisi hidrogeologi lokal; sistem akuifer seperti pola aliran air tanah, dan kualitas air tanah ;kondisi geologi ; mengetahui karakteristik akuifer; mengetahui distribusi sumber zat pencemar; menunjukkan potensi pencemaran air tanah. Parameter-parameter tersebut berupa klasifikasi, pemodelan, intensitas, dan waktu pencemaran yang dianalisa dengan menggunakan metode Johansson dan Hirata (2002). Hasil dari penelitian berupa peta potensial pencemaran. Tipe dari tanah di daerah penelitian adalah pasir halus, sedang dan pasir kasar. Pada daerah penelitian terdapat muka air tanah yang dangkal, akuifer tertekan dimana zat pencemar dapat masuk ke bawah permukaan. Konsentrasi nitrat sebagian besar lebih dari 50 mg/L yang berasal dari septic tank, yang mana kedalamannya terletak pada zona unsaturated. Beberapa sumur gali terletak kawasan industri batik dimana konsentrasi Pb dan Cr tinggi telah melewati ambang batas WHO. Dan konsentrasi fenol lebih dari 0,001 mg/L yang dapat berasal dari kebocoran dari SPBU

Most of drinking water and water usage in Yogyakarta Urban Area are derived from groundwater sources and water supply. As the rapid increasing of population and human developments due to leakage from unsewered sanitation system, train fuel storage tanks, waste water from batik industries, and applying the fertilizer for agriculture, it affected to the degradation of groundwater quantity and quality. The main objectives of groundwater contaminant loading assessment are identify the contaminant sources, with the causes of contaminant loading to subsurface, to evaluate the concentration of contaminant from sources with its related pathways and rate of downward movement of contaminant, identify the existing sources of contaminant, provide an understanding of the local hydrogeological condition; aquifer system such as groundwater flow pattern and groundwater quality; elucidate the role of geological conditions in the contaminant loading; understand the aquifer characteristics; determine the distributions sources of contamination; assess the contaminant loading potentials; show the potential of groundwater contaminant loading to the sources. The components are the classification, mode of disposition, intensity, and duration of contaminant load are analyzed by using Johansson and Hirata method (2002). The outcome of assessment is the map of the contaminant loading potential. Mostly of soil types are sandy loam, loamy sandy, and some sandy. Furthermore, I this site had found shallow groundwater table, unconfined aquifer, which contaminant can leak to subsurface. The concentration of nitrate is mostly higher than 50 mg/l because of hydraulic loading from private septic tanks area, which the depth description was located at unsaturated zone. Some wells located behind the home batik industry associated with the higher concentration of Pb and Cr was higher than WHO Standard Guide value because of coloring processes. And also phenol concentration was higher than 0.001 mg/l that can leak from oil station by accident spillage.

Kata Kunci : Hidrogeologi,Kualitas Air Tanah,Zat Pencemar,contaminant loading, quality of groundwater, contaminant sources