Sustainable management of biological solids in small treatment plants: overview of strategies and reuse options for a solar drying facility in Poland

Abstract

The issue of sustainable management of biosolids (excess sludge) from wastewater treatment is an important issue in the entire developed world. Residual sludge disposal costs and environmental impact may be significant, and reducing such costs, as well as the energy consumption for dewatering and drying, is a key issue for safe and sustainable sludge disposal, considering the recent ban of some disposal options, such as landfilling, in many European countries. An alternative to thermal technologies is solar drying (not to be confused with bio-drying, very close to the concept of composting). Solar greenhouse drying technology is characterized by reduced land requirements compared with traditional outdoor drying beds, as well as by low-energy requirements compared with other thermal drying methods. Process operation is cost-efficient, with close to no maintenance, and observed specific evaporation rates up to threefold higher than conventional drying beds. Many applications of this technology exist in Poland, Germany and Austria: more than 10,000 t of wet sludge per year is treated in this way in Germany alone and almost as many (9000 t/year) in Poland. This paper examines current biosolids treatment technologies applicable to small wastewater treatment plants (2000-9999 population equivalents served) and opportunities for possible solids reuse in Poland in view of sustainable circular economy schemes. In particular, a purely solar-driven greenhouse facility for sewage sludge drying was investigated under different conditions (season, temperature, environmental humidity) and possible improvements for its efficiency evaluated. Sludge processed by solar drying could have different final disposal pathways, according to season, in accordance with the prescriptions of the new National Waste Management Plan of Poland.

Solar drying of granulated waste blends for dry biofuel production

“…The drying time for sewage sludge alone may also last from a few to more than 30 days. For example, Boguniewicz-Zablocka et al (2020) report solar drying of municipal sewage sludge containing 88% water and arranged in 5-mm layer under the Polish weather conditions and with outdoor temperature < 20 C takes roughly 4 weeks.…”

Environmental impacts assessment of wastewater treatment and sludge disposal systems under two sewage discharge standards: A case study in Kunshan, China

“…A possible alternative can be is solar drying of the sludge. Solar greenhouse drying technology is characterized by reduced land requirements compared with traditional outdoor drying beds, as well as by low-energy requirements compared with other thermal drying methods (Boguniewicz-Zablocka et al, 2020). But it still requires a lot of lands compared to direct incineration.…”

“…Process operation is cost-efficient, with close to no maintenance, and observed specific evaporation rates up to threefold higher than conventional drying beds. However, this approach has one major drawback: drying efficiency depends on the degree of irradiation and temperature, which vary throughout the year (Boguniewicz-Zablocka et al, 2020).A potential solution is to adopt the membrane bioreactors (MBRs) to reduce the production of sludge. However, MBRs have shortcomings of high energy consumption and high consumables (Zheng et al, 2018), and these shortcomings need to be overcome.…”

Investigating the Quality and Efficiency of Biosolid Produced in Qatar as a Fertilizer in Tomato Production

“…The necessity of developing agriculture has become a requirement in recent decades as a way to cope with population growth worldwide. The deterioration of arable lands and the excessive usage of pesticides and agrochemical fertilizer, along with the related dynamic factors such as climate changes, are the reasons behind many global catastrophes [1]. There are signs of our success in managing some of these catastrophes as well as signs of our failures in many more.…”

“…The incorporation of sewage products into agricultural practices has gained traction in many parts of the world. Scientists and researchers have influenced rules and regulations for this application by proposing new methods of sewage treatment, specifying the application rate, choosing certain types of crops to be fertilized, arranging for tests, and evaluating the potential impacts on the environment and human health as part of a holistic approach [1]. The use of biosolids as organic fertilizer has also gained popularity as a sustainable approach for enhancing soils toward increasing crop yields as well as to meet the increased demand for urban greenery programs.…”