Abstrak Penelitian ini bertujuan untuk mengetahui pengaruh dari variabel kekasaran saluran dan suhu air sungai terhadap perubahan kualitas air Sungai Winongo untuk parameter Chemycal Oxygen Demand (COD) dan Total Suspended Solid (TSS Abstract The objective of the study is to determine the effect of roughness variables and temperature to water quality of Winongo River for parameters of Chemycal Oxygen Demand (COD) and Total Suspended Solid (TSS). The analysis that have used is descriptive by comparing the result of modelling scenarios concentration using QUAL2Kw software at every variable with roughness variation at 0,016; 0,04, and 0,15. Result of river water temperature variation at 24,2 o C; 28,1 o C; and 30,6 o C. The modelling result shows that the effect of channel roughness alongside with river physical condition has a big effect on pollutant concentration at water body with closing the value of roughness on natural stream at 0,15 (sig >0,05). The river water temperature will follow the stream movement and discharge of pollutant that enter the water body with balancing the river physical condition that cause a turbulence on water body and has a direct effect with a small cause against COD and TSS (sig > 0,05), The Winongo river water body quality change could be known from a graphic and output value from QUAL2Kw software. With strategy management it may be closed the physical condition into it naturally condition that will be decreasing the value of pollutant concentration and increasing the river water quality into a better quality

Drinking water treatment sludge (DWTS) is a waste by-product from water treatment plants where aluminum and iron salts are the most commonly used coagulants. DWTS was reused to investigate the effects of DWTS on the digestion liquid quality and microorganism activity of excess activated sludge (EAS). DWTS with four suspended solid (SS) concentrations (0%, 2%, 5% and 10%) was added to EAS which was sampled during aerobic and anaerobic digestion processes, then batch tests were carried out which followed the coagulation-flocculation process. It was found that DWTS can improve total dissolved nitrogen (TDN) and dissolved phosphorus (DP) removal efficiencies for anaerobic EAS. The highest removal efficiency of TDN (29.97%) as well as DP (55.38%) was observed when DWTS dosage was SS = 10%. The release of dissolved organic matter (DOM) by DWTS could increase dissolved organic carbon (DOC) concentration and lead to the accumulation of non-biodegradable humic acid-like substance in aerobic and anaerobic digestion liquid. The dehydrogenase activity (DHA) values of anaerobic EAS were higher than aerobic EAS. DWTS could reduce DHA for both EAS. These results indicate that potential risk of release of DOM should be considered when reusing DWTS in future research.

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This research focuses on characterizing the dissolved organic matter found at water treatment plants with closed systems. Recycled water generated as a by-product of water treatment is added to raw water in those systems. The dissolved organic matter in the raw water was found to be higher in summer than in winter, but the water treatment process was able to produce purified water of the similar quality in both seasons. The recycled water contained mostly low molecular weight and protein-like substances, and this composition was different from that of the raw water, which mainly contained humic-like substances. The recycled water did not influence the concentration of humic-like substances or the molecular weight distribution in the influent water.