Feasibility Study on Wastewater Treatment Using Chemically Enhanced Primary Treatment

A techno-economic analysis was performed to investigate wastewater treatment feasibility using chemically enhanced primary treatment (CEPT) compared to conventional primary treatment (PT). An experimental study was conducted to investigate the performance of CEPT at optimum conditions, and experimental results were used to feed the techno-economical study with required input data. The wastewater treatment was focused on reducing BOD5, COD, and TSS. The comparison between CEPT and PT was concerned with removal efficiency and process economics. CEPT process has shown better efficiency compared to PT process. The experimental work indicated that ferric chloride is the optimum coagulant agent since it is highly efficient and available at a low cost. The optimum coagulant experimental results showed that the turbidity removal efficiency was 82%, COD removal 84%, BOD removal 68.1%, and SS removal 85%. The techno-economic study was performed to investigate the feasibility of CEPT. The techno-economic evaluation indicated that CEPT is a cost-effective and technically viable process for wastewater treatment. The techno-economic evaluation indicated that CEPT is a cost-effective and technically viable process for wastewater treatment as the operating cost can be reduced by 66% compared to PT.

Combining Process Modelling and LCA to Assess the Environmental Impacts of Wastewater Treatment Innovations

Alternative wastewater treatment (WWT) technologies with lower environmental impacts seem to be the way forward in the pursuit of sustainable wastewater treatment plants (WWTPs). Process modelling of material and energy flows together with life-cycle assessment (LCA) can help to better understand these impacts and show the right direction for their development. Here, we apply this combined approach to three scenarios: conventional WWT; conventional WWT + chemically enhanced primary treatment (CEPT); conventional WWT + CEPT + side stream partial nitritation/anammox (PN/A). For each scenario, equations were developed to calculate chemical oxygen demand and nitrogen flow (solid and dissolved form) through the WWTP and to estimate the energy demands of its unit operations. LCA showed that the main environmental impact categories for all scenarios were global warming potential (GWP), eutrophication potential (EP) and marine aquatic eco-toxicity potential (MAETP). Compared with conventional WWT, CEPT and CEPT combined with PN/A resulted in a higher sum of normalized and weighed environmental indicators, by 19.5% and 16.4%, respectively (20.0% and 18.3% including biogenic carbon). Interestingly, the environmentally positive features of the alternative scenarios were often traded-off against other increased negative impacts. This suggests that further development is needed to consider these technologies a sustainable alternative.

Towards an Energy Self-Sufficient Resource Recovery Facility by Improving Energy and Economic Balance of a Municipal WWTP with Chemically Enhanced Primary Treatment

The recent trend of turning wastewater treatment plants (WWTPs) into energy self-sufficient resource recovery facilities has led to a constant search for solutions that fit into that concept. One of them is chemically enhanced primary treatment (CEPT), which provides an opportunity to increase biogas production and to significantly reduce the amount of sludge for final disposal. Laboratory, pilot, and full-scale trials were conducted for the coagulation and sedimentation of primary sludge (PS) with iron sulphate (PIX). Energy and economic balance calculations were conducted based on the obtained results. Experimental trials indicated that CEPT contributed to an increase in biogas production by 21% and to a decrease in sludge volume for final disposal by 12% weight. Furthermore, the application of CEPT may lead to a decreased energy demand for aeration by 8%. The removal of nitrogen in an autotrophic manner in the side stream leads to a further reduction in energy consumption in WWTP (up to 20%). In consequence, the modeling results showed that it would be possible to increase the energy self-sufficiency for WWTP up to 93% if CEPT is applied or even higher (up to 96%) if, additionally, nitrogen removal in the side stream is implemented. It was concluded that CEPT would reduce the operating cost by over 650,000 EUR/year for WWTP at 1,000,000 people equivalent, with a municipal wastewater input of 105,000 m3/d.