Performance of very small wastewater treatment plants with pronounced load variations

Abstract

The operation of very small biological wastewater systems is strongly influenced by the patterns of wastewater generation. The absence of people in the connected building(s) during holidays or off-season leads to a system underload, other circumstances however may lead to an overload. Experiments have been carried out to display the effects of no-feed conditions on activated sludge biomass and its microbial activity during a 24 hour period after re-feeding. The decrease of the biomass during idle periods can be modelled by a first order equation. The initial specific oxygen uptake rate (OUR) of the remaining biomass decreased with the duration of the preceding no-feed sequence. Four different laboratory-scale treatment plants were operated to demonstrate the system performance when re-started after a break period of 24 and 52 days respectively. The effluent concentration after a break of 52 days had not been sufficient as compared to the discharge requirements given by German laws. In addition a full scale trickling filter was monitored, while the connected building accommodated a maximum of 40 guests interrupted by times with no guest at all. Conclusions are drawn from the experimental results and from literature, giving some hints on how to manage the impacts of varying loads at very small wastewater treatment plants.

Evaluating the Performance of Small Wastewater Treatment Plants

“…Compared to our study, the number of measured field data used for the performance evaluation in other studies was very small (e.g., Hellström and Jonsson, 2004;Karczmarczyk et al, 2021). Other studies such as Kegebein et al (2007) aimed to monitor the treatment performance during specific loading scenario, i.e. non-loading periods.…”

“…However, they did only use literature data for the performance of the systems. Kegebein et al (2007) evaluated the performance of four technologies (i.e., trickling filter, RBC, CAS and a moving bed biofilm system) using measured data from lab-scale experiments with defined loading of the systems. Main objective of their study was to test the behaviour of the plants during and after non-loading periods.…”

Sustainable Biogas Production Potential from Urban Wastewater in Nepal

“…The dense settlements in a large city or area may need to install several DEWATS system within their region. DEWATS is widely used not only in developing countries, but it is also widely accepted in developed countries as well [10].The decentralized technology is best suited in receiving human excreta and wastes as potential resources and solving sanitation issues as close as possible to the source of generation [11].The major advantages of the DEWATS systems are as follows [12], [13]:…”

Improving and upgrading an existing activated sludge with a compact MBBR – disc filters parallel line for municipal wastewater treatment in touristic alpine areas

“…Besides fulfilling existing legal requirements, it is ecologically relevant to reduce human impacts on natural environments and water. These areas pose additional issues for wastewater treatment such as extreme seasonal load variations, low temperatures and a challenging orography (Wett et al 2002;Kegebein et al 2007). Moreover, the increased touristic activity and the impact of climate change on peak loads have already outdated several existing CAS plants (Weissenbacher et al 2008).…”