The integrated monitoring system of water quality is eminently reliant on water quality trend data. This study aims to obtain water quality patterns related to land-use change over a periodic observation in the Opak sub-watershed, Indonesia, both from a seasonal and spatial point of view. Landsat image data from 2013 to 2020 and water quality data comprising 25 parameters were compiled and analyzed. This study observed that land use remarkably correlated to water quality, especially the building area representing the dense population and various anthropogenic activities, to pollute the water sources. Three types of pollutant sources were identified using principal component analysis (PCA), including domestic, industrial, and agricultural activities, which all influenced the variance in river water quality. The use of spatiotemporal-based and multivariate analysis was to interpret water quality trend data, which can help the stakeholders to monitor pollution and take control in the Opak sub-watershed. The results investigated 17 out of 25 water quality parameters, which showed an increasing trend from upstream to downstream during the observation time. The concentration of biological oxygen demand over five days (BOD5), chemical oxygen demand (COD), nitrite, sulfide, phenol, phosphate, oil and grease, lead, Escherichia coli (E. coli), and total coli, surpassed the water quality standard through spatial analysis.

Abstract. LPG gas is the main fuel used in households. These days LPG gas leak triggered an accident that resulted in huge losses, especially if the accident occurred within the dense housing. LPG gas leakage monitoring and early detection of a gas leak and a leak warning is needed to prevent more fatal accident. Wireless sensor networking is a technology that can be used to build a centralized monitoring system by using a microcontroller as the interface and control system. This research developed system device monitoring and early detection of gas leaks by utilizing gas sensors MQ-4 and AVR microcontroller family as control devices. The system is also equipped with XBee PRO S2B nirkable devices as the interface to the wireless networking system that is used to transmit sensor data from the detection point to the monitoring center equipped with a PC and software integrated Visual Basic. Gas leak alert is sent with the message formats through social networking Gtalk.

Biogas adalah gas mudah terbakar yang dihasilkan dari proses fermentasi bahan-bahan organik oleh bakteri anaerob. Dengan kandungan utama berupa gas metana, biogas mempunyai potensi yang sangat besar untuk dikembangkan sebagai sumber energi alternatif. Pemanfaatan biogas sebagai sumber energi dapat dilakukan secara langsung, dengan membakar biogas tersebut, atau secara tidak langsung dengan mengubahnya menjadi bentuk energi lain seperti listrik. Sebagian warga Dusun Kaliurang Timur, Kelurahan Hargobinangun, Kecamatan Pakem, Sleman selama ini telah memanfaatkan biogas secara langsung. Studi terdahulu pada lokasi yang sama (Yulianto dan Purnomo, 2009) menunjukkan potensi biogas yang dapat dihasilkan oleh 54 ekor sapi di dusun tersebut adalah 362,88 m 3 /hari. Studi lanjutan ini bertujuan untuk mengkaji pemanfaatan biogas di dusun tersebut dengan mengonversi terlebih dahulu menjadi energi listrik. Kajian dilakukan pula pada estimasi pembangkitan daya, jenis mesin penggerak, dan analisa ekonomi. Dari volume biogas yang diproduksi per hari diperkirakan energi ini setara dengan listrik sebesar 18,75 kW. Sedangkan dari analisa teknis dan ekonomis, mesin penggerak pembangkit listrik berbahan bakar biogas skala rumah tangga yang cocok dikembangkan di Dusun Kaliurang Timur adalah menggunakan mesin diesel dengan estimasi pembangkitan daya sebesar 3kW dan waktu operasional 12 jam/hari. Kondisi ini layak secara ekonomi layak dengan BC ratio 1,76 serta simple pay back 1,9 tahun.

Carbon monoxide (CO) is an odorless, tasteless and colorless gas in which it is difficult to be recognized by human beings. CO gas that enters the human body at a certain concentration has negative impact on health. A monitoring system which can recognize the amount of CO gas concentration, especially for the indoor is needed to cope with this problem. In this paper, monitoring system is designed using XBee as a data transmission medium. Three XBee are integrated with the sensor node circuits, microcontroller as a data processor and one XBee as a data collector. The sensor nodes consist of an LM35DZ temperature sensor, a humidity sensor HSM 20-G and a CO sensor TGS 2600. The data are read by sensor nodes and then they are transmitted wirelessly using XBee. The data collector functions as the receiver, processor and data viewer in the form of tables and graphs using Visual Basic 6.0. From this design, the results of data transmission can be displayed in the form of graphs and tables which are then stored into the database. The data transmission range is ± 53 meters indoor, where the average error TGS 2600 sensor reading is 4.414 %.

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