China
Africa
Explore chapters and articles related to this topic
Activated Sludge Process (ASP)
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
One of the most common tests for monitoring the operation of an aeration system is the settlement test, as shown in Figure 24.4. This procedure involves determining the MLSS concentration by running a solids test. Sludge settlement is measured by observing the volume of settled sludge in a graduated cylinder filled with 1 litre of mixed liquor. The volume of settled solids after 30 minutes of settling is used to calculate the index. The sludge volume index (SVI) is the volume in millilitres occupied by one gram of settled suspended solids. Sludge density index (SDI) is the inverse of SVI expressed as percent solids. SVI=VSSLMLSSasmL/gSDI(%)=1SVI×100%
Aerobic Biotreatment of Wastewater
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
The sludge volume index (SVI) is a measure of sludge settleability. It is the volume occupied by 1 g of sludge after 30 min of sedimentation. The normal range of SVI for sludge in an aeration tank is 50–150 mL/g of biomass (MLVSS). When the concentration of biomass in an aeration tank is 3 g/L and the SVI is 70 mL/g of biomass, the volume of settled activated sludge in the settling tank is 500 ml/L = 50% of the volume of settling tank; the concentration of biomass in the bottom part of the settling tank is twice as big as in the aeration tank. When the concentration of biomass is 5 g/L and the SVI is 200 mL/g of biomass, the volume of settled activated sludge in the settling tank is 1 L/L = 100% of the volume of settling tank, which means that there is no separation of biomass and treated wastewater.
Biological Waste Treatment
Published in Syed R. Qasim, Wastewater Treatment Plants, 2017
The most accurate method of determining the return sludge is based on determination of sludge volume index (SVI), which is defined as the volume occupied in milliliters by 1 g of settled sludge. It is also defined by the ratio of percent volume occupied by settled sludge in 30 min and MLSS concentration in percent. The SVI test has been used traditionally to determine the settling behavior of MLSS. An SVI below 100 is an indication of excellent settling sludge. Poor settling is characterized by high SVI. At SVI values above 200, the sludge from a conventional aeration basin does not settle well and fills up the clarifier. The return sludge ratio is calculated from Eq. (13-29): () QrQ=[100MLSSconcentration%×SVI − 1] − 1
Tracing morphological characteristics of activated sludge flocs by using a digital microscope and their effects on sludge dewatering and settling
Published in Environmental Technology, 2023
Yuki Nakaya, Jinming Jia, Hisashi Satoh
Generally, municipal and industrial wastewater treatment plants (WWTPs) are subjected to biological treatment, in which pollutants such as chemical oxygen demand (COD), phosphorus, and nitrogen are degraded or removed by microbial activity [1]. After the completion of biological treatment, it is crucial to separate the biomass [activated sludge (AS)] from the supernatant to obtain a clear effluent. Often, the separation of AS from the liquid phase includes two steps. First, AS is separated from the liquid phase by gravity settling in a clarifier. The worse sludge settleability would cause a turbid effluent and biomass washout [2], thereby affecting treatment performance. The sludge volume index (SVI) is mainly used as an indicator for sludge settleability. If the SVI is high, the sludge settleability will worsen, and the risk of biomass washout will be high. Second, the excess AS can be further dewatered for final disposal or additional treatment. Worse dewaterability would increase the total treatment costs; excess AS treatment contributes almost half to the wastewater treatment cost [3], even though worse dewaterability may not affect the effluent water quality. To evaluate dewaterability, time to filtration (TTF), specific resistance to filtration (SRF), and capillary suction time (CST) are generally considered. Under the same measurement conditions, high values of TTF, SRF, or CST suggest the worse sludge filterability and dewaterability.
Application of real-time nitrogen measurement for intermittent aeration implementation in a biological nitrogen removal system: performances and efficiencies
Published in Environmental Technology, 2019
R. Ferrentino, M. Langone, M. Vian, G. Andreottola
In addition, sludge settling properties were also monitored considering the trend of the sludge volume index (SVI). Value higher than >150 mL g−1 indicated sludge with poor settleability [32]. In this study, scarce sedimentation and separation between sludge and supernatant in secondary sedimentation was observed during the reference period (SVI was 222 ± 58 mL g−1). According to other studies [13], the retrofitting of the WWTP with the implementation of intermittent aeration allowed to improve the sludge/water separation performance and to stably maintain throughout the intermitted aeration period (SVI of 137 ± 17 mL g−1).
Aerobic granular sludge formation in a sequencing batch reactor treating agro-industrial digestate
Published in Environmental Technology, 2021
Alessandra Carucci, Giovanna Cappai, Giovannimatteo Erby, Stefano Milia
Sludge volume index (SVI) was determined by reading the height of the settled bed after 5 and 30 min settling and calculated from the settled bed volume and the dry weight in the reactor. The ratio SVI5/SVI30 was also calculated and used as an indication of sludge bed compactness.