Maximising biogas in anaerobic digestion by using engine waste heat for thermal hydrolysis pre-treatment of sludge

Abstract

Dublin's Ringsend WWTP was designed to serve a population of approximately 1.2 million p.e. with a sludge production of 37,000 dry tonnes per year after upgrading to full secondary treatment. Several technical solutions were put forward as part of a design, build, finance and operate (DBFO) competition, with the chosen solution being a proposal by Black and Veatch for a combination of sequencing batch reactor (SBR) technology and anaerobic digestion with Cambi thermal hydrolysis pre-treatment (THP). The THP plant was built by Cambi and handed over to B&V in 2002. The plant is now operated by Celtic Anglian Water. In September 2004 a test was carried out on the mass and energy balance of the plant following 2 years of operation and is detailed in this paper. The process enables digestion at very high dry solids feed and low hydraulic retention time. The plant was built with three digesters of 4250 m3 each and is fed with hydrolysed sludge at 11% DS. There are four no. 1 MW Jenbacher engines operating mainly on biogas. Each pair of engines is fitted with a waste heat boiler with a capacity of one tonne steam per hour. These boilers have sufficient capacity to provide 80% of the steam required for the THP, which in turn provides all the heat for the subsequent digestion in the form of hydrolysed feed. There are two main biogas boilers for top up steam and other uses of the biogas including thermal oxidation of concentrated odours.

Effects of dilution ratio and Fe0dosing on biohydrogen production from dewatered sludge by hydrothermal pretreatment

“…were fitted well to Equation (2) except the result at the ratio of 4:1 (R 2 = 0.8299). The lag time was longer (3-5 days) in this study, whereas using waste rich in carbohydrate (rice powder and lettuce powder) as a substrate took only 3-11 h. [22] A longer time was needed for hydrogenproducing anaerobes to restore in sludge which included complex organics. Table 4 shows the characteristics of sludge solutions after the fermentation.…”

“…This technology could even be found in industrial application such as Dublin's Ringsend wastewater treatment plant. [22] In the process of hydrothermal pretreatment, macromolecule organics in sludge were degraded and converted into short chain matters such as VFAs causing a drop in the pH value. However, the release of amino acids provided a buffering capacity, so the pH decreased to not less Downloaded by [Eindhoven Technical University] at 16:31 02 February 2015 Table 2.…”

Pretreatment of High‐Solids Wastes/Residues to Enhance Bioenergy Recovery

“…The Naestved WWTP (Denmark) implemented the thermal hydrolysis process upstream of existing anaerobic digesters to reduce biosolids for recycling. A comparison of digestion performance between conventional and thermally treated solids at the Ringsend STW shows VSR improvements between 42 and 62% following thermal hydrolysis (Pickworth et al 2005). The installation at HIAS, Norway, has also been achieving VSR from 60 to 65% (Panter 2001).…”

Improving efficiency of transport fuels production by thermal hydrolysis of waste activated sludge

“…The most used technology nowadays is CAMBI TM (Figure 1) process (more than 30 operating facilities) [6]. Previously dewatered sludge enters the pulper, where it is mixed and heated with recycle steam from the reactors and the flash tank.…”