Effect of recirculation ratio on the performance of modified septic tank in treating office building wastewater

Vandith Va,Ahmad Soleh Setiyawan,Dyah Wulandari Putri,Prayatni Soewondo,A Soleh Setiyawan,M Sonny Abfertiawan,D Roosmini,H Dwi Ariesyady,A Nastiti

doi:10.1051/e3sconf/202014801001

Vandith Va, Ahmad Soleh Setiyawan + Show 7 more

Open Access

https://doi.org/10.1051/e3sconf/202014801001

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Abstract

Higher concentration of nutrients has been characterized from office buildings compared to domestic wastewater. A Modified Septic Tank (MST), which consists of anoxic conditions followed by a Moving Bed Biofilm Reactor (MBBR) is proposed to treat office wastewater. This research investigated the effect of Recirculation Ratio (RR) on organic and nutrient removal in MST. The synthetic wastewater with COD: TN: TP (252:85:3), which is similar to actual office wastewater was used. The experimental data were obtained from three RR values (2, 3 and 4). The results showed COD, TN, NH4, and TP removal ranged from 88% to 90%, 64% to 78%, 68% to 86%, and 56% to 64%, respectively. The effluent concentrations of COD and NH4 ranged from 21 to 30 and 9 to 23 mg/L after applying RR and from 19 to 24 and 27 to 29 mg/L without RR, respectively. RR had the significant effect on organic and nutritional removal (p <0.05). It suggested increasing RR could improve nutrient removal in MST and the stability of NH4 in the effluent needs to be considered.

Highlights

The wastewater from office building is different from the characteristic of domestic wastewater
2.1 Location and Period of Research This research has been conducted in the water quality laboratory of the study program of environmental engineering at Institute of Technology Bandung (ITB) with a duration of 4 months from December 2018 to March 2019. 2.2 Lab-scale Reactor Setup The lab-scale of the modified septic tank consists of four compartments: anoxic 1, anoxic 2, Moving Bed Biofilm Reactor (MBBR) and sedimentation compartment while the conventional septic tank has only anaerobic compartment
The average COD removal was 90%, 89% and 88% when the system was operated with recirculation ratio of 4, 3 and 2, respectively shown in Fig 3, To investigate the effect of recirculation ratio on COD removal in Modified Septic Tank (MST), oneway analysis of variance (ANOVA) was performed, and it gave the significant difference on COD removal in MST and maximum removal of COD can be achieved 90% at Recirculation Ratio (RR) of 4 (P value = 2E-05 < 0.05)

Summary

Introduction

The wastewater from office building is different from the characteristic of domestic wastewater. Conventional Septic Tank (CST) is the most popular primary treatment method for on-site domestic wastewater treatment. The treatment of household wastewater by CST had been conducted, but the treatment performance is not sufficient in terms of organic and nutrient removal [2, 16,17,18]. Bouted and Ratanatamskul (2018) [3] conducted research on a new isolated anaerobic filter (IAF) system incorporating waste heat input for wastewater treatment for buildings, but the performance of organic and nutrient removal from this system is still low

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