Experimental Application of a Laboratory SBR Plant Used for Domestic Wastewater Treatment

NARCIS BARSAN1, DANA CHITIMUS1*, FLORIN MARIAN NEDEFF1*, ION SANDU2,3, MIRELA PANAINTE LEHADUS1, ANDREI VICTOR SANDU3,4, OANA IRIMIA TARTOACA1 1Vasile Alecsandri University of Bacau, 157, Calea Marasesti Str., 600115 Bacau, Romania 2Alexandru Ioan Cuza University of Iasi, Arheoinvest Interdisciplinary Platform, Scientific Investigation Laboratory, 11 Carol I Blvd., 700506 Iasi, Romania 3Romanian Inventors Forum, 3 Sf. Petru Movila St., Bloc L11, III/3, 700089, Iasi, Romania 4Gheorghe Asachi Technical University of Iasi, Materials Science and Engineering Faculty, 53A D. Mangeron Blvd., 700050, Iasi, Romania

The water problems management is an actual issue all over the world. The developed countries involve modern strategies to perform the water and wastewater infrastructures management. The good practice strategies applied in the west of EU countries can offer some models for east European countries where the water and wastewater management still present some real problems if we consider the real investments and the how the actual infrastructure perform.
The problems of water and wastewater management in Romania, as a part of east European countries with real issue in these sector, can be divided in two major direction: new investments (considering the European strategies and founds) and national performance strategies (by introducing the regional and national monitoring plans to obtain maximum performance for the actual infrastructure and human resources involved).
To resolve the wastewater problems in the small localities the SBR (Sequencing Batch Reactor) plant can be taken into consideration.
Unlike conventional mechanical-biological systems, where the treatment process (aerobic and/or anaerobic) is divided into several tanks, in the case of an SBR plants the treatment is divided by operation times. Thus, the SBR wastewater treatment systems can be an alternative to the conventional wastewater treatment systems with the variables for inlet. This method, unlike continuous treatment systems, can be easier adapted to inlet concentration variation [15][16][17][18][19][20][21][22].
In an SBR wastewater treatment installation, the treatment takes place under automatic control, the biological reactor being the main element of the system. The SBR systems treatment process is divided by using a single basin, with sequential operation times. A complete cycle is filling, reaction (aerobic/anaerobic), settling and treated wastewater evacuation. One of the most important advantages of SBR systems include the possibility of operating cycle time modify [15][16][17][18][19][20][21][22].
This paper aims to identify the possibility of a real operation condition (by using domestic wastewater) for a small SBR treatment system, by evaluation of some physical and chemical wastewater parameters.

Experimental part Materials and methods
The research was oriented to the use of a small Sequencing Batch Reactor (SBR) treatment system utilized in a real working condition for domestic wastewater treatment. In these sense, real wastewater from Vasile Alecsandri Universisty of Bacau campus were used. For a proper SBR installation work, we use a septic tank as pretreatment method [18].
To avoid the process perturbation the installation was placed in a controlled closed location and the wastewater were pumped in the septic tank by simulating a real condition use for a 5 to 7 equivalent inhabitants (figure 1). The volume of the wastewater treated in the experimental installation was kept constant during the experiment at a level of 0.27 m 3 /operating cycle. Taking into account the five operation phases of an SBR system, an operating cycle of the experimental installation consists of: SBR compartment filling without wastewater mixer; The reaction phase, with aerobic and anaerobic conditions; The settling; Treated wastewater evacuation, the treated water is evacuated from the top of the basin without the active sludge from the bottom [18].
A specific operation time of the plant refers to the sludge recirculation phase, in the septic compartment, that occurs after each cycle. This sludge recirculation ensures inoculation for septic tank to accelerate the biological processes. The operation times for SBR cycle are presented in Table 1. To evaluate cycle times in the SBR in some wastewater parameter reduction, the experimental period of 60 days, was divided into three stages (table 1) [18].
The wastewater monitored parameters were temperature: pH, total solid suspension, BOD 5 , COD, ammonium nitrogen and total phosphorus. To perform these parameters measurements were used the equipment's: OxiTop (respirometric method to measure the BOD 5 ) (figure 2 a), inoLab Multi Level 1 (for pH) (figure 2 b) and Odyssey DR/2500 (COD, ammonium nitrogen and total phosphorus (TP) determination) (figure 2 c) [18].

Results and discussions
Considering the operation key parameters and process, the SBR plant were inoculated two weeks before experiment. At the end of each experimental period (20 days) the wastewater parameter was determined both for inlet and effluent. The parameters values variation are presented in figures 3 and 4 [18,23,24].
From the below figures it is observed that the wastewater used in the experimental study (inlet) is under NTPA 002 limit values for four quality indicators. Even though, the values presented in the graph show that the wastewater used in the study present qualitative variations over time. Also, the effluent parameters (TSS, BOD 5 and NH 4 + ) values are over NTPA 001 limit in all cases. The inlet parameter values ( figure 3) were specific for a domestic wastewater, but for a low flow, we can consider that, the measured values, are difficult to treat in small plants. Even if in the third experimental period we obtain the lower concentration for all parameter of the effluent, the excess of the NTPA 001 limits can be a result of the plant operation performances for the wastewater type. Operation times cycle modification reveal that it is very important to establish some optimum conditions in the process in special in the cases of low flow treatment.
From the table 2 it is observed that pH value is according with NTPA 001 and 002 limits and the wastewater The biological processes are directly influenced by wastewater temperature in special for low flow treatment. The Figure 5 present the analyzed parameters reduction (%).
From the below graph can be observed that the reduction is relatively in the same range for all wastewater quality indicators. The most visible increase is observed in the case of the first and the second experimental period when we obtain differences especially in the case of BOD 5 , COD and NH 4 + . Also, the data presented in the graph show that in the first subperiod, were obtained 48 to 50% reduction were obtained for four all analyzed indicators. In the second period, reduction over 60% were obtained for two quality indicators analyzed. In all three experimental period it is observed that the lowest reduction was obtained for phosphorus, below 50%.

Conclusions
The SBR plant and experimental procedures proved some real possibilities to treat low flow domestic wastewater in real conditions. Even if the SBR plant are adaptive at flow variation we obtain relative low reduction for evaluated wastewater quality analyzer parameter. This aspect can be a consequence of the inoculation period (was used only insitu inoculation) and of the low wastewater temperature (with a very important role in pre-treatment and biological processes).
Continuous monitoring of the SBR operation cycle times and how the physical and biochemical processes can be influenced, creates the possibility of identifying methods to reduce plant working time and to increase wastewater parameter reduction.