Operation and Control of a Full‐Scale Biogas Plant Treating Wastewater from the Cleaning of Car Tanks

Abstract

A 1200‐m3 full‐scale biogas plant treating highly polluted wastewater (WW) from the cleaning of tank cars transporting food and fodder is working stably and efficiently despite the WW is constantly varying in strength and composition, is easily acidifying, and low in alkalinity. Na2CO3 has to be added to maintain the digester alkalinity and the digester pH at defined values due to softened water used for car tank cleaning. Monitoring volatile organic acid concentration and controlling the alkalinity in the digester are essential for maintaining the digestion process stability. Biogas production is adapted to the demand by a modulated feeding regime. The drastic modulation of feeding is possible due to the moderate organic loading of the plant along with the high average hydraulic retention time.

Integration of Artificial Intelligence into Biogas Plant Operation

“…In the studies performed, it was found that pH is not an early instability detection parameter, relying on organic loads due to its instability [100,101]. In addition to the pH measurements, alkalinity measurements, which are essential for early detection of process instability, can be conducted via electrical conductivity measurements on real time basis [102,103]. Moreover, a Fourier Transform Infra-Red (FT-IR) spectrometer can be installed in the reactors to detect Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), Volatile Fatty Acids (VFA), and Partial and Total Alkalinity (PA and TA) [104].…”

Phase Separation in Anaerobic Digestion: A Potential for Easier Process Combination?

“…An accumulation of acids inside a tank does not necessarily mean an immediate decrease of the pH-value. Any drop in the pH-value exhibits severe imbalances, which cannot be rapidly counteracted and typically need several days or even weeks to recover (Pfeiffer et al, 2020). In that case, the OLR has to be decreased significantly, even the addition of anti-foam agents might be needed due to increased cell lysis rates and protein excretion (Moeller and Zehnsdorf, 2016).…”

“…For all AD applications, especially for FW-treating digesters, the amount of produced SCCAs is a proper parameter to observe the process functionality (Pfeiffer et al, 2020). An adequate amount of the effluent from the acidogenesis needs to be transferred to the second (or third) stage in order to prevent starvation in the methanogenic stage without the risk of its acidification.…”