Treatment of seawater salinity sewage with intermittent sand bioreactors

In water stressed areas, flush toilets using fresh water are unsustainable. This paper explores the ability of intermittent sand bioreactors (ISBs) to treat seawater salinity septic tank effluent for on-site wastewater treatment in coastal regions. Two ISB designs, sand only and layered sand and gravel, are compared for treatment efficacy. Six columns of each design were constructed in the laboratory and dosed four times per day, for a total hydraulic loading rate of 4 cm/day, with artificial seawater salinity septic tank effluent over 21 months. Average TOC and ammonia removal for both designs averaged >90% and >96%, respectively. No statistically significant difference existed in the percent removal or effluent concentrations between the two designs. Half of the columns of each design produced effluent with >4 mg/L ammonia at least once during the study, resulting in discontinuation of wastewater application for seven weeks. This resting approach resulted in effective treatment for up to 9 months (limited by the end of the study). The results indicate that both ISB designs can treat artificial seawater salinity septic tank effluent, but that an additional 1/3 capacity is needed to maintain a consistent hydraulic loading rate while accounting for resting ISBs when treatment efficacy declines.

Optimization of Biofilter Size for Aquaponics Using Genetic Algorithm

Unlike a media-filled aquaponic system, the nutrient film technique (NFT) and deep water culture (DWC) require the installation of an external biofilter to provide sufficient area for nitrifying bacteria colonization, which is essential for the conversion of toxic ammonia from fish waste into nitrate that is easily assimilated by plants. Given the importance of biofilters, it is imperative to properly design this tank to effectively support the nitrification process. Several factors need to be considered for the biofilter design. Thus, an optimization algorithm can be used to obtain combinations of the design parameters. The genetic algorithm (GA) is a heuristic solution search or optimization technique based on the Darwinian principle of genetic selection. The main goal of this study was to obtain the optimal biofilter size for a given fishpond volume and the amount of ammonia to be treated. The conversion coefficient in the Michaelis–Menten equation was used as the fitness function in this study. The parameters optimized using GA include the hydraulic loading rate, height of the biofilter, and predicted ammonia concentration. For the given assumption of a 60 kg feed introduced to the system and a 1500 L fishpond, the hydraulic loading rate, biofilter height, and final concentration of ammonia were 0.17437 m, 0.58585 m, and 0.01026 ppm, respectively. Using the values obtained from running the GA, the optimum biofilter volume for the system was 0.4608 m3, whereas the water flow rate was 0.03 L/min. For recommendations, multiple objective GAs can be used to add cost-related variables in the optimization because they have not yet been considered in the computation.

PENGARUH HYDRAULIC LOADING RATE (HLR) TERHADAP PENGOLAHAN LEACHATE DENGAN MENGGUNAKAN METODA MULTI SOIL LAYERING (MSL)

Leachate atau lindi sampah berpotensi untuk mencemari air pemukaan dan air tanah. Hal ini diakibatkan degradasi biologis leachate menghasilkan pencemar berbahaya seperti zat organik dan logam berat. Penelitian ini bertujuan untuk mengamati efisiensi MSL dalam mereduksi pencemar yang terkandung dalam leachate. Pengamatan penelitian difokuskan pada pengaruh hydraulic loading rate (HLR) terhadap efisiensi reduksi pencemar, yang terdiri atas 250 l/m2.hari, 500 l/m2.hari dan 1000 l/m2.hari. Penelitian ini dilakukan dengan cara mengalirkan secara gravitasi leachate Tempat Pemprosesan Akhir (TPA) Talang Gulo ke reaktor MSL berdimensi 15x50x50 cm. Reaktor MSL terdiri atas lapisan impermeable dan lapisan permeabel. Lapisan impermeabel merupakan lapisan yang terdiri atas campuran tanah dan arang dengan rasio 2 : 1, serta lapisan permeabel terdiri atas lapisan zeolit berdiameter 0,25 – 0,5 cm. Berdasarkan hasil penelitian, didapat bahwa MSL dapat menetralkan pH dan mereduksi konsentrasi pencemar COD, amoniak, besi (Fe) dan warna. Efisiensi reduksi untuk semua pencemar berkisar 92% – 99,966%. Secara umum, HLR sangat mempengaruhi efisiensi reduksi, dimana makin rendah HLR maka makin rendah konsentrasi outlet serta makin tinggi efisiensi reduksi.

PENGARUH HYDRAULIC LOADING RATE (HLR) TERHADAP PENGOLAHAN LEACHATE DENGAN MENGGUNAKAN METODA MULTI SOIL LAYERING (MSL)

Leachate atau lindi sampah berpotensi untuk mencemari air pemukaan dan air tanah. Hal ini diakibatkan degradasi biologis leachate menghasilkan pencemar berbahaya seperti zat organik dan logam berat. Penelitian ini bertujuan untuk mengamati efisiensi MSL dalam mereduksi pencemar yang terkandung dalam leachate. Pengamatan penelitian difokuskan pada pengaruh hydraulic loading rate (HLR) terhadap efisiensi reduksi pencemar, yang terdiri atas 250 l/m2 .hari, 500 l/m2 .hari dan 1000 l/m2 .hari. Penelitian ini dilakukan dengan cara mengalirkan secara gravitasi leachate Tempat Pemprosesan Akhir (TPA) Talang Gulo ke reaktor MSL berdimensi 15x50x50 cm. Reaktor MSL terdiri atas lapisan impermeable dan lapisan permeabel. Lapisan impermeabel merupakan lapisan yang terdiri atas campuran tanah dan arang dengan rasio 2 : 1, serta lapisan permeabel terdiri atas lapisan zeolit berdiameter 0,25 – 0,5 cm. Berdasarkan hasil penelitian, didapat bahwa MSL dapat menetralkan pH dan mereduksi konsentrasi pencemar COD, amoniak, besi (Fe) dan warna. Efisiensi reduksi untuk semua pencemar berkisar 92% – 99,966%. Secara umum, HLR sangat mempengaruhi efisiensi reduksi, dimana makin rendah HLR maka makin rendah konsentrasi outlet serta makin tinggi efisiensi reduksi.

Carbon Source Competition in Biological Selenate Reduction under Other Oxyanions Contamination

Selenate removal in drinking water is being vigorously debated due to the various health issues concerned. As a viable treatment option, this study investigated a fixed-bed biofilm reactor (FBBR) with internal recycling. The experimental design tested how hydraulic loading rate and electron donor affect selenate reduction together with other oxyanions. The tested accompanying oxyanions were nitrate and perchlorate and experiments were designed to test how an FBBR responded to the limited electron donor condition. The results showed that the reactor achieved almost complete selenate reduction with the initial hydraulic loading rate of 12 m3/m2/day (influent concentration of 1416 µg SeO42−/L). Increasing the hydraulic loading rates to 16.24 and 48 m3/m2/day led to a gradual decline in selenate removal efficiency. A sufficient external carbon source (C:N of 3.3:1) achieved an almost complete reduction of nitrate as well as selenate. The FBBR acclimated to selenate instantaneously and reduced nitrate via synergistic denitrification. An experiment with another oxyanion addition, perchlorate (459 µg ClO4−/L), revealed that perchlorate-reducing bacteria were more strongly associated with carbon limitation than selenate-reducing bacteria, which can help us to understand parallel reactions in FBBRs. This research provides a framework to further study the use of electron donor-controlled FBBRs for simultaneous reduction of selenate and other oxyanions threatening the drinking water-related environment and public health.