This paper evaluates environmental conditions responsible for the high concentrations of trace metals in Indonesian coastal groundwater. Indramayu, which has significant potential groundwater resources, but for which limited information is available regarding its vulnerability, is selected as our study area. Results show that Fe²⁺ and Mn²⁺ are natural contaminants in the groundwater of the study site. The correlations of trace metals with salinity and redox-sensitive parameters verify that saline water has a significant impact upon the dissolution of Fe and Mn. Furthermore, reductive condition is confirmed to be responsible for Fe and Mn dissolution with a less significant correlation compared to salinity. Moreover, the high concentrations of trace metals are coupled with high dissolved organic carbon (DOC), which indicates that reductive environment may arise because of organic-matter decomposition. Finally, the impact of human activity upon Fe and Mn dissolution is identified at the northern tip of Indramayu, where trace-metal contents are significantly elevated. Further, in the southern part, the groundwater condition is relatively more natural; thus, the impact of human activity upon the presence of Fe and Mn is lesser in this region.

The origin of ammonium-nitrogen in Indonesian coastal groundwater has not been intensively examined, meanwhile the elevated concentration remains a concern. This research aims at tracing the potential sources of ammonium-nitrogen in the groundwater of Indramayu, Indonesia where groundwater is vital for livelihood. From results, a combined examination of nitrogen isotope, coliform bacteria, land-use, and geology confirmed the natural and anthropogenic origins of ammonium-nitrogen in the groundwater. In the brackish-water aquaculture region, groundwater has δ¹⁵N_NH4 values from +1.8 to +4.8‰ signifying that ammonium-nitrogen is derived from mineralization of organic nitrogen to ammonium. Furthermore, ammonium has a significantly positive relationship with sodium indicating the exchangeable ammonium is mobilized to groundwater via cation exchange. Meanwhile ammonium-nitrogen from anthropogenic waste was detected in agricultural and residential region. The groundwater has more varied δ¹⁵N_NH4 values, from −2.9 to +16.1‰, which implies attenuation of ammonium-nitrogen from several sources namely manure, mineral fertilizer, sewage, and pit latrines. Also, the presence of E. coli confirms the indication of human and animal waste contamination. However, since ammonium has no relationship with sodium, cation exchange is not feasible and ammonium-nitrogen flows into the groundwater from anthropogenic sources along with liquid wastes.

PENGOLAHAN AIR LIMBAH TEKSTIL MELALUI PROSES KOAGULASI – FLOKULASI DENGAN MENGGUNAKAN LEMPUNG SEBAGAI PENYUMBANG PARTIKEL TERSUSPENSI (Studi Kasus: Banaran, Sukoharjo dan Lawean, Kerto Suro, Jawa Tengah)

The Cirasea River can provide water for both the Bandung basin and agricultural irrigation. Intensive agriculture, industry, and land use changes could have an impact on water quality. The purpose of this study is to look at the origins of heavy metals in riparian water resources. Heavy metal analysis was performed on 13 groundwater and river water samples. Heavy metals in water sources were compared with sediment and soil. The samples were analyzed for heavy metals using an AAS instrument. The research method employs statistical, geographical, and heavy metal pollution index (HPI). The HPI for river water was 131, whereas groundwater was 93. River water with an HPI value of more than 100 is highly polluted, indicating that it is unsafe for human consumption and has negative health consequences. Data verification with heavy metals in sediments reveals the presence of heavy metals coming from geogenic circumstances in various locations in the upstream area. Heavy metals in downstream areas result from geological factors and anthropogenic activities in the surrounding area. The long-term effects of heavy metal pollution along the riparian zone will become apparent. More research is needed on communities that depend on groundwater supplies along the Cirasea watershed.