Enhancing phenol removal from waste water by adding powder activated carbon to the lab-scale activated sludge system

In this study, the commercial powder activated carbon (PAC) was added to a bench scale conventional activated sludge (CAS) system to enhance phenol removal. The mixed liquor suspended solid (MLSS) concentration of CAS with adding PAC was stable in all stages of operation, while MLSS concentrations in CAS without PAC addition sharply decreased as the Phenol loading reached 1.8 g phenol/L.day. Higher removal of chemical oxygen demand (COD) and Phenol achieved with the CAS by PAC addition compared with those achieved with CAS without PAC addition. The difference in COD removal efficiency was 7 - 9% in stages 3 and 4 (0.8 and 1.2 g phenol/L.day, respectively), and about 33% in stage 5 (1.8 g phenol/L.day). The advantage of CAS with PAC addition was clearly observed in the highest phenol loading (1.8 g phenol/L.day) because the MLVSS/MLSS ratio of CAS with PAC addition increased and the COD and phenol removal efficiencies kept stable in this stage, while reverse trends were found for CAS without PAC addition. The results indicated that the adaptive ability of the CAS by adding PAC was significantly higher than the CAS without AC addition. This study offers useful preliminary results for applying a hybrid system between CAS and adsorption with PAC for further research and application in future.

Treatment of Domestic Wastewater with Fixed Bed Biofilm Reactor

Fixed bed biofilm reactors were evaluated with three different arrangements of bio-balls. The performance of different arrangements was evaluated based on chemical oxygen demand (COD), total suspended solid (TSS) and mixed liquor suspended solid (MLSS). The three rectors were fabricated and operated in lab scale model with real domestic wastewater. Considering the TSS removal efficiency, arrangement one was the best followed by arrangement two and arrangement three. While for COD, arrangement one recorded the highest removal efficiency followed by arrangement two and column. The average COD concentration for arrangement one was 23 while for arrangement two and arrangement three was 25 and 36 mg/l respectively. The overall average effluent TSS concentrations for the arrangement one, two and three were 25, 32 and 45 mg/l respectively. TSS and COD removal was almost the same for arrangement one and arrangement two but arrangement one has the highest among them, and all removal is acceptable under Malaysian standards. Besides that, all the three arrangements have the differences in terms of maintenance and installation. There was no clogging occurred in all the three arrangements.

Aktivitas Mikroba Lumpur Aktif Konsentrasi Tinggi Pada Sistem Lumpur Aktif- Membran

Pengolahan air limbah dengan sistem kombinasi proses lumpur aktif dengan membrane telah banyak dimanfaatkan di beberapa negara maju. Sistem ini diketahui mampu beroperasi dengan konsentrasi lumpur aktif (MLSS, Mixed Liquor Suspended Solid) sangat tinggi sehingga menghasilkan sistem yang kompak dengan efisiensi pengolahan tinggi. Penelitian ini mengkaji aktifitas mikroba yang terlibat dalam sistem. Aktifitas yang dikaji antara lain laju pemanfaatan oksigen spesifik (SOUR, specific oxygen uptake rate), parameter kinetika, serta laju pemanfaatan nitrogen dan fosfor.Proses pengolahan berjalan pada konsentrasi MLSS jauh di atas proses lumpur aktif konvensional, yaitu berturut-turut 18.400, 22.900, 24.300, dan 25.500 mg/l. Untuk mendapatkan konsentrasi MLSS tersebut, proses pengolahan beroperasi pada waktu tinggal cairan (HRT, hydraulic retention yime) 24 jam dan waktu tinggal sel (SRT, solid retention time) 8, 16, 24, dan 32 hari. Hasil penelitian menunjukkan bahwa mikroorganisme yang terlibat pada proses ini ditandai oleh mikroorganisme yang mempunyai laju pertumbuhan sangat lambat. Parameter kinetika yang diperoleh sebagai berikut: laju pertumbuhan maksimum spesifik (μmax) 0,024 jam-1, koefisien perolehan sel (Y) 0,515 (mg sel/ mg COD), konstanta setengah jenuh (Ks) 589 mg/l, dan laju kematian spesifik (b) 0,010 jam-1. Dengan semakin tinggi konsentrasi lumpur aktif, maka aktifitas mikroba akan semakin kecil. SOUR yang diperoleh untuk SRT 8,16,2 dan 32 hari berturut-turut sebesar 0,612; 0,357; 0,279; 0,207 gO2 / (gMLSS.hari). bila ditinjau dari segi operasionalisasi unit pengolahan limbah, maka proses pengolahan lumpur aktif – membran jauh lebih menghemat kebutuhan nitrogen dan fosfor untuk nutrient.Kata kunci : aktifitas mikroba, sistem lumpur aktif-membran, SOUR

Simulasi dan Pemodelan Proses Lumpur Aktif Tanpa Resirkulasi Lumpur Pada Keadaan Transien

Pemodelan dan simulasi pada keadaan transien dilakukan terhadap sistem pengolahan air limbah dengan proses lumpur aktif tanpa resirkulasi lumpur. Model matematika pada keadaan transien disusun dengan membuat neraca massa substrat dan neraca massa sel. Persamaan yang diperoleh diselesaikan secara numerik. Beberapa parameter yang digunakan untuk penyusunan modelyaitu konsentrasi COD umpan 2.000 mg/l dan waktu tinggal cairan (Hydraulic Retention Time, HRT) bervariasi dari 8, 16, 24 hingga 32 hari. Konsentrasi mikroba (Mixed Liquor Suspended Solid, MLSS) awal divariasikan dari 250, 500, 1000 hingga 2000 mg/l. substrat terlarut awal di dalam bak aerasi divariasi dari 100, 300, 500 hingga 1000 mg/l. Parameter kinetika yang digunakan diperoleh dari literature yaitu laju pertumbuhan maksimum spesifik, laju kematian specific, koefisien perolehan sel dan konstanta setengah jenuh masing-masing 0,589 hari-1, 0,248 hari-1, 0,515 (mg sel/ mg substrat) dan 589 mg/l.Hasil simulasi menunjukkan bahwa waktu yang diperlukan untuk mencapai keadaan tunak tergantung pada HRT dan MLSS awal di dalam bak aerasi. Konsentrasi COD dan MLSS di dalam bak aerasi pada keadaan transien tergantung pada MLSS dan konsentrasi COD terlarut awal di dalam bak aerasi dan SRT. Dari hasil simulasi ini bias diambil rele of thumbs bahwa waktu yang diperlukan untuk mencapai keadaan tunak adalah sebesar 1-3 kali HRT pada HRT rendah satu kali HRT pada HRT tinngi.Kata kunci : simulasi dan pemodelan, proses lumpur aktif, keadaan transien

PENGARUH CO-PRECIPITATION BESI KLORIDA TERHADAP KINERJA LUMPUR AKTIF PADA PROSES PENGOLAHAN AIR LIMBAH DOMESTIK SINTETIK

The increase of population leads to an increase of the quantity of domestic wastewater. Activated sludge system is the most cost-efective to treat the domestic wastewater treatment. This study is aimed to evaluate the co-precipitation coagulant effect of FeCl3 on the growth of activated sludge, settling characteristics of the activated sludge, and effluent quality. sludge sedimentation characteristics (settling) as well as on the effluent quality. The activated sludge systems were operated in batch mode and synthetic domestic wastewaters with C:N:P ratio of 100:5:1 were used as feed wastewater. The growth of activated sludge was based on concentration of Mixed Liquor Suspended Solid (MLSS), settling characteristics of activated sludge was based on value of Sludge Volume Index (SVI), and effluent quality was based on turbidity, colour, N-ammonia concentration, and Chemical Oxygen Demand content. Results indicate that inhibition effect of FeCl3 to activated sludge activity was not significant at dosage ≤ 30 mg/L. Good settling characterisic (SVI 70-150 mg/L) was achieved at dosage of 20-30 mg/L. Finally, the best effluent quality, i.e. turbidity (9.4), colour (96), amonia removal (83.6%), and COD removal (72.97%), at dosage of 30 mg/L. Keywords: activated sludge; co-precipitation; domestic wastewater; wastewater treatment Abstrak Peningkatan jumlah penduduk mengakibatkan kenaikan jumlah air limbah domestik. Sistem lumpur aktif merupakan proses yang paling efektif untuk mengolah air limbah domestik. Penelitian ini bertujuan untuk mengevaluasi pengaruh co-precipitation koagulan FeCl3 terhadap pertumbuhan lumpur aktif, karakteristik pengendapan lumpur aktif, dan kualitas efluen. Sistem lumpur aktif dioperasikan secara curah dan umpan air limbah yang digunakan adalah air limbah domestik sintesis dengan rasio C:N:P = 100:5:1. Pertumbuhan lumpur aktif berdasarkan konsentrasi Mixed Liquor Suspended Solid (MLSS), karakteristik pengendapan lumpur berdasarkan nilai Sludge Volume Index (SVI), dan kualitas efluen berdasarkan tingkat kekeruhan, warna, kadar N-amonia dan kadar Chemical Oxygen Demand (COD). Hasil penelitian menunjukkan bahwa inhibisi FeCl3 terhadap aktivitas lumpur aktif tidak signifikan pada dosis ≤ 30 mg/L. Karakteristik pengendapan yang baik (SVI 70-150 mg/L) tercapai pada dosis 20-30 mg/L. Kualitas efluen terbaik, yaitu kekeruhan (9,4), warna (96), penyisihan amonia (83,6%) dan penyisihan COD (72,97%), pada dosis 30 mg/L. Kata kunci: lumpur aktif; co-precipitation; air limbah domestik; pengolahan air limbah

Study on Simultaneous Nitrification–Denitrification in Membrane Bioreactor

This study was conducted to evaluate the performance of membrane bioreactors (MBR) for organics and nitrogen removal. The membrane bioreactor was fed with domestic sewage and operated at different contents of dissolved oxygen (DO), different hydraulic retention time (HRT), and various mixed liquor suspended solid (MLSS) concentrations. The results showed that the distribution of DO level in MBR imposed a significant effect on simultaneous nitrification–denitrification (SND), and the optimal DO concentration should be controlled between 0.5 mg/L to1 mg/L. The denitrification was found to show the best performance for total nitrogen (TN) removal when the HRT reached 5 hours. Higher MLSS concentration led to the improvement in TN removal and the optimal MLSS concentration was 9000mg/L. In fact, more than 90% Chemical Oxygen Demand (COD) and ammonia nitrogen (NH3-N) were reduced when the MLSS concentration exceeded 3000mg/L.

Investigation of Oxytetracycline (OTC) Removal Effectiveness of Aerobic Units and it’s Measurement Optimization

In order to study the effectiveness of aerobic units in removing oxytetracycline(OTC) and explore the effective method to measure OTC in wastewater, the different level of mixed liquor suspended solid(MLSS) and aeration quantity are test in OTC degradation in aerobic unit, the measuring methods are tested and optimized. The result shows that with the condition of (1)extraction buffer solution of NaCl(1mol/L) : oxalic acid(0.5mol/L) : ethanol = 25/25/50,v/v/v; (2) water(added phosphoric acid, pH=3) and acetonitrile as flow phase (V:V=75:25); (3) wavelength at 343 nm could achieve 0.9995 correlation coefficient between the concentration of OTC in the sample and peak area measured. The degradation/removal rate was influenced by aeration intensity, detention time and the mixed liquor suspended solids(MLSS) in the treatment units, and higher removal rate was obtained under the higher concentration of oxygen, MLSS and OTC condition.