Assessment of the Efficiency, Environmental and Economic Effects of Compact Type On-Site Wastewater Treatment Plants—Results from Random Testing

Agnieszka Karczmarczyk,Anna Baryła,Agnieszka Bus

doi:10.3390/su13020982

Agnieszka Karczmarczyk, Anna Baryła + Show 1 more

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https://doi.org/10.3390/su13020982

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Abstract

This study presents the results of random testing of selected on-site wastewater treatment plants (WWTPs) constructed in Poland in Masovia Voivodship in the years 2011–2016. The vast majority of tested on-site WWTPs were compact (container) type treatment plants, based on low rate activated sludge (AS), sequencing batch reactors (SBR), or a hybrid (activated sludge supported with biological film, AS + BF) method. Compact type plans are becoming more and more popular in single households in Poland, due to the option of co-financing. According to certificates provided by producers and distributors, container on-site wastewater treatment plants are efficient in BOD5 removal, with the expected removal rate being over 80%. The aim of this study was (1) to analyze BOD5 in effluents sampled from randomly selected on-site WWTPs, (2) to evaluate predicted and real environmental effects of the implementation of on-site WWTPs in selected communes within Masovia Voivodship, and (3) to calculate unit environmental and economic effects of container on-site WWTPs in three different technologies. Results of this study show that in most cases, there is a gap between the declared and the real BOD5 removal efficiency. There is also a difference between the performance of different container type technologies. The lowest real environmental effect was obtained for AS technology, and the highest for the hybrid one. The predicted environmental effect has only been almost achieved in the case of hybrid systems. Based on net present value (NPV) benefits, technologies can be set up as follows: AS > SBR > AS + BF, making the AS method the most effective technology from the point of view of the economy.

Highlights

Small wastewater treatment plants (WWTPs) must treat domestic wastewater before it can be discharged into a receiver
For small WWTPs, a wide range of different cleaning methods is available for use e.g., single-stage trickling filter systems, rotary dipping body plants, plants with submerged fixed bed, systems with freely movable growth bodies, activated sludge plants in the stock-up operation, combination systems, pass-activated aeration plants, and membrane-activated aeration plants [1] which are commonly known as compact or container type on-site wastewater treatment plants
The results showed that the lowest real environmental effect was obtained for activated sludge (AS) technology, and that there is a significant statistical difference between AS and AS + biological film (BF) performance at the 95% confidence level (Figure 4)

Summary

Introduction

Small wastewater treatment plants (WWTPs) must treat domestic wastewater before it can be discharged into a receiver. For small WWTPs, a wide range of different cleaning methods is available for use e.g., single-stage trickling filter systems, rotary dipping body plants, plants with submerged fixed bed, systems with freely movable growth bodies, activated sludge plants in the stock-up operation, combination systems, pass-activated aeration plants, and membrane-activated aeration plants [1] which are commonly known as compact or container type on-site wastewater treatment plants. The most popular solutions for single households are low-rate activated sludge (AS), sequencing batch reactors (SBR), and plants with submerged fixed bed or freely movable growth bodies known as hybrid plants (AS + BF). Calculations were made for three different technologies used in compact type on-site wastewater treatment systems: AS—

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