To make the adsorption process more economic and environmental friendly, it is necessary to study desorption and reutilization of the adsorbents. In the present study, the effectiveness of natural pumice in removal of iron from aqueous solution was investigated in several sorption-desorption cycles. The desorption characteristics of previously adsorbed iron ions on natural pumice were tested by various desorbing agents such as HCl, NaOH and aquadest. Among them, HCl showed the highest desorption efficiency (37.89%) with 0.1 M of concentration and 60 min of contact time. The removal efficiency of iron ions in reused natural pumice could be maintained up to 90% in the third cycle of adsorption. The results indicate that although complete desorption was not achieved, natural pumice from Sungai Pasak, West Sumatra, Indonesia, can be sufficiently reused up to three cycles of adsorption-desorption.

Adsorption of iron from aqueous solution by using maize husk (Zea mays L.) as a low-cost adsorbent was studied. Batch experiments were carried out at ambient temperature, 0.075-0.250 mm of particle size and 100 rpm of agitation speed to determine the influence of initial pH, adsorbent dose, initial concentration and contact time on the removal of iron. Langmuir and Freundlich models were applied to describe the adsorption isotherm of iron by maize husk. The results showed that optimum condition of iron removal were 4 of pH solution, 20 g/L of adsorbent dose, 10 mg/L of Fe concentration and 15 min of contact time of adsorption with 0.499 mg Fe/g maize husk of adsorption capacity. Experimental data fitted well to Langmuir's adsorption equilibrium isotherm within the concentration range studied. This study demonstrated that maize husk, which is an agricultural waste, has potential for iron removal from groundwater or other polluted waters.

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This study aims are toanalyze the spatial variation of electrical conductivity (EC) values, total suspended solids (TSS), and total dissolved solids (TDS) concentrations along the Batang Arau River. Water samples were collected from eight stations along the river at biweekly intervalsbetween March and May 2014. The results indicate an increasing trend in the value of three parameters from upstream to downstream, reflecting the effect of natural and anthropogenic activities along the river. The EC values were in the range of 173-5,097 μS/cm and had exceeded the water quality standard established by World Health Organisation (WHO) at the downstream. The TSS and TDS concentrations were in the range of 76-2,078 mg/L and 124-3,560 mg/L, respectively. The TSS concentrations at all stations had exceeded the river quality standard of class II established by Governor Regulation of West Sumatera, while the TDS concentrations had exceeded only at the downstream area. Significant spatial variation of the EC and TDS concentrations was observed between the upstream-midstream and the downstream but was not obtained along the river for the TSS concentrations. It indicates that the anthropogenic activities along the river affected the variability of EC and TDS, but not for TSS. Based on these results, reducing the number of sampling points into three stations could be performed for the EC and TDS, while TSS monitoring at only one station could be applied.

To investigate the potential of adsorption and regeneration of natural pumice from West Sumatera Indonesia for total chromium (Cr) removal from aqueous solution, batch experiments in multiple adsorption-desorption cycles were performed. The results indicated that the optimum condition of total Cr removal were 3 of pH solution, 0.3 g/L of adsorbent dose, 60 min of contact time of adsorption, <63 ?m of diameter of adsorbent, and 1 mg/L of total Cr initial concentration with 2.226 mg Cr/g pumice of total Cr uptake. The experimental data obtained were fitted with the Freundlich adsorption isotherm within the concentration range studied. Desorption efficiencies for total Cr ions by using 0.1 M HCl as desorbing agent were in the range of 31-32%. Although complete desorption were not attained, the natural pumice could be sufficiently reused up to 3 cycles of adsorption- desorption with increasing trend in total Cr uptake that may due to the surface modification of natural pumice caused by HCl. Overall results revealed that easy availability of natural pumice as local mineral in West Sumatra, Indonesia and its ability to adsorb and retain total Cr will create more interest to develop new natural adsorption method of pollutant removal from solution.

ABSTRAKDalam penelitian dilakukan pengolahan limbah cair Hotel yang bersumber dari dapur dan laundri dengan metode Multi Soil Layering (MSL). Tujuan penelitian ini untuk menentukan efisiensi penyisihan COD dan mempelajari pengaruh faktor variasi material organik dalam campuran tanah pada lapisan anaerob dan variasi Hydraulic Loading Rate (HLR) terhadap efisiensi pengolahan limbah cair hotel dengan metode MSL. Dua buah reaktor MSL berdimensi 50 x 15 x 100 cm dengan lapisan batuan yang sama pada kedua reaktor berupa kerikil berukuran 35 mm serta lapisan anaerob berupa campuran tanah dengan arang (reaktor 1) dan campuran tanah dengan serbuk gergaji (reaktor 2) dengan rasio komposisi 2 : 1. Limbah dialirkan pada masing-masing reaktor dengan variasi HLR 500, 750, dan 1.000 l/m2hari. Konsentrasi COD sebelum diolah adalah 132,600201,240 mg/l, setelah diolah dengan MSL konsentrasi berubah menjadi 12,48088,920 mg/l. Secara umum, variasi material organik dalam campuran tanah tidak begitu berpengaruh pada penyisihan COD. Variasi HLR cukup berpengaruh, dimana HLR 500 l/m2hari memberikan efisiensi penyisihan COD yang lebih tinggi. Efisiensi penyisihan COD yang diperoleh pada penelitian ini berturut-turut pada reactor 1 berkisar antara 55 -90 % dan pada reactor 2 berkisar antara 56-89%. Hasil menunjukkan bahwa kedua reaktor mampu menyisihkan COD pada limbah cair hotel.Kata Kunci: COD, limbah cair hotel, multi soil layering (MSL)ABSTRACTResearch COD removal from hotel wastewater stemmed from laundry and kitchen with Multi Soil Layering method (MSL) was conducted. The aim were to observe COD removal efficiency and to study the effect of organic material variation in soil as the anaerob layer as well as the effect of various hydraulic loading rate (HLR). In this research, there were two MSL reactors with dimension of 50 x 15 x 100 cm. Aerob layers of both reactors in the form of gravel 3-5 mm sized while anaerob layers are composed from soil mixed with charcoal (reactor 1) and soil mixed with sawdust (reactor 2) with ratio 2:1. HLR of wastewater for each reactor are 500, 750, and 1.000 l/m2day. Concentration of COD was 132,600-201,240 mg/l. COD concentration successively reduced to 12,480-88,920 mg/l.This result indicated both reactors can cast aside COD and also neutralize hotel liquid waste pH. In general, organic material variation of in soil mixture, that is sawdust and charcoal did not show any significant influence. HLR of 500 l / m2/day allowed the best removal efficiency at each contaminant parameters. As a whole efficiency removal of COD at this research successively at reactor 1 ranged from 55-90%, and 56-89%.Key Words:COD, hotel wastewater, multi soil layering (MSL)

This paper aims to assess metallic pollution in the Batang Arau River, an important source of freshwater supply for local communities in West Sumatera, Indonesia, by applying multivariate statistical techniques. Sampling was conducted at eight stations along the river from March to May 2014. The results indicate that all the metals studied have similar spatial distribution patterns, with an increasing trend in concentration from upstream to downstream. Total concentration of six metals studied upstream, as background concentration, was 1.050 mg/L, and increased to 2.249 mg/L downstream. Spatial distribution of metals did not show significant variability (p < 0.05) for Cd, Cr, Fe, and Pb, but Co and Mn did. The results of principal component analysis/factor analysis (PCA/FA) and correlation analysis suggest that Cd, Co, and Fe are originated from natural and anthropogenic sources; Cr and Pb are derived from natural sources; and Mn is controlled by anthropogenic sources.

As an effort for water resources conservation, a fixed-bed column was applied to remove nitrate from groundwater using pumice as adsorbent. The column performances were evaluated by varying the influent concentration (50 mg/L dan 80 mg/L) and influent flow rate (2 - 3 gpm/ft2 equal to 43–65 mL/min) with 85 cm of adsorbent bed depth. The results indicated that the increase in influent concentration increased the amount of nitrate and cause the earlier breakthrough time. Furthermore, the increase in influent flow rate caused the column exhaustion time to occur earlier resulted in the shortened lifespan of the column. The column system with a bed depth of 85 cm and flow rate of 2 gpm/ft2 (43 mL/min) for 80 mg/L of influent concentration showed the best nitrate uptake performance in this study with a total removal of 31.42% and adsorption capacity of 1.394 mg/g. The results revealed that the pumice in column has potential for nitrate removal from groundwater.