Increasing the sludge energy potential of wastewater treatment plants by introducing fine mesh sieves for primary treatment

Abstract

The objective of this study was to compare some basic characteristics of sludge from fine mesh sieves (sieve sludge) with sludge from primary clarifiers (primary sludge) regarding their energy potential with a focus on anaerobic digestion and/or incineration. Nineteen samples of sludge from fine mesh sieve plants (most of them without fine screens and grit chambers as pre-treatment) and 10 samples of primary sludge were analysed for the content of dry solids (DS), volatile solids (VS), chemical oxygen demand (COD), calorific value and methane potential. The results demonstrated that the sieve sludges have significantly higher VS content and higher methane potential than primary sludges, clearly indicating an increased sludge energy potential if fine mesh sieves are used for primary treatment instead of primary clarifiers at wastewater treatment plants with anaerobic digesters. If the sludges from primary treatment are to be incinerated or used as fuel in cement kilns, there is no significant difference in energy potential (given as calorific values) for the two types of primary treatment.

Organic carbon recovery modeling for a rotating belt filter and its impact assessment on a plant-wide scale

“…It may be because of the double layer formation when a thick mat is allowed on the belt surface which leads to overall higher TSS and COD removal from primary treatment. Some papers [6,9] also indicate the same analogy as observed in scenario -3.…”

“…It is (as shown in Figure 1) predominantly used as a mechanical treatment with special focus on achieving a higher suspend solids removal, and it works based on cake filtration and sieving (more discussion on the working principle is presented in the materials and methods sec-tion). The sludge collected from the RBF is enriched in cellulose fibers (approximately 80 -90 % of the recovered organic mass [1,2]) and has significantly higher volatile solids content with excessive methane production potential compared to sludge collected from a traditional primary clarifier (PC) (cellulose fiber fraction is only 30 -40% of recovered organic mass) [1,6]. In a traditional WWTP, the PC is one of the unit operations (for primary treatment) which works based on gravity separation to remove total suspended solids (TSS) and lower the biological oxygen demand.…”

Is SCENA a good approach for side-stream integrated treatment from an environmental and economic point of view?

“…To do so, in scenario 2A sludge dynamic thickening (SDT) was considered as an effective technology to increase the total solids (TS) concentration of the mixed sludge by up to 5%; in scenario 2B, chemically assisted primary sedimentation (CAPS), consisting of adding chemicals in order to increase the coagulation, flocculation and sedimentation of raw wastewater, was simulated. The application of CAPS was chosen since it does not require any further significant structural intervention, thus saving investment costs and footprint (De Feo et al 2012); finally, in scenario 2C, the primary sedimentation tank was replaced by a rotating belt screen (RBS) system in order to improve the performance of primary treatment (removal of TS up to 70%) without use of chemicals (Paulsrud et al 2014). The CAPS system, apart from TS and chemical oxygen demand (COD), can enhance also the removal of P from wastewater.…”

Effects of naturally occurring grit on the reactor performance and microbial community structure of membrane bioreactors

“…For instance, the VSS/TSS in a wastewater treatment facility in a megacity of south China decreased to as low as 0.45 during the wet season because of the inflow of grit-carrying storm water [4]. The decreased VSS/TSS will decrease the sludge energy potential during the anaerobic digestion of excess activated sludge [5]. The accumulation of grit in biological treatment compartment is expected to change the properties of the sludge and the bacterial community, affecting the performance of the reactor.…”