Environmental impact of two ways of treating domestic wastewater with an example of a conventional treatment plant versus plant-pond sewage treatment

One of the important metter of environmental care is effective sewage treatment. Centralised sewage treatment with high efficiency dominates in Poland. However, highly dispersed properties often require the use of other alternative solutions. The aim of the paper is to compare the impact of two sewage treatment methods on the environment: conventional (PWWTP) and plant-pond (PPST). To assess the operation of both treatment plants and their environmental impact, emergy calculation and emergy indicators such as ELR, EYR, and ESI were used. It was found that the PPST treatment plant burdens the environment less. The current operation of the conventional treatment plant absorbs over 87% of the total emergy, while in the case of the biological treatment plant it is 0.40%. ELR for PPST was 5.58, while for PWWTP it was as much as 1809.09. The efficiency of sewage treatment in both treatment plants is similar. BOD5 reduction was 87.5% for PPST and 96.7% for PWWTP. For both treatment plants, an attempt was made to identify other environmental benefits, such as the generation and use of by-products, the possibility of using treated sewage for irrigation purposes or creating a biodiversity site. An attempt was made to quantify some of the additional benefits.