The impact of chemically enhanced primary treatment on the downstream liquid and solid train processes

Abstract

The use of chemical coagulants and flocculants to supplement chemically enhanced primary treatment (CEPT) processes is increasing in popularity as it has been demonstrated to improve carbon redirection and suspended solids and phosphorus removal. Dosing 15 mg ferric chloride/L of wastewater and poly aluminum chloride (PACl; 0.5 mg/L) to the influent of a primary clarifier successfully achieved improved carbon redirection and suspended solids removal at a full‐scale WWTP. In this study, the impacts of PACl on the downstream liquid and solid train processes of the same WWTP were investigated. Compared to FeCl3 addition, a combined PACl and FeCl3 addition to the primary influent reduced the TSS and TP concentrations of the secondary clarifier effluent by 20% and 33%, respectively. Effluent BOD5 and ammonia‐nitrogen concentrations of the downstream activated sludge process were not affected by the addition of a combined FeCl3 and PACl in the primary clarifier. PACl addition affects the bioavailability of carbon and hence reduced the methane production efficiency of the primary sludge by 20%–30%. However, the significant amount of carbon concentrated in the CEPT sludge would enhance the amount of energy recovered through incineration. Practitioner points The chemically enhanced primary treatment process is an attractive method for carbon redirection and energy recovery. The combined FeCl3 and PACl addition in the primary clarifier improves the full scale activated sludge process effluent quality. PACl has a negative effect on methane production.

Investigating phosphorus loads removed by chemical and biological methods in municipal wastewater treatment plants in Poland

“…It should be noticed that the location of coagulant dose is also an important factor that affects the nal P bioavailability. Chemically enhanced primary treatment (CEPT), also known as pre-coagulation is increasing in popularity due to the carbon redirection opportunities and limited metal transfer to excess sewage sludge (Shewa et al 2020). In 4 of the analyzed WWTPs CEPT process was applied, and therefore in Lublin-Hajdów (600 000 PE), Elbląg (141 500 PE), Brwinów (190 000 PE) and Zamość (250 000 PE) WWTPs, where 569,47 Mg of P per year is removed P recovery with crystallization-based methods using the sludge from their secondary settling tanks, might be used, while it should have a lower content of metal-P complexes (Dong et al 2019).…”

Coagulation-Flocculation: A potential Application for Mosquito Larval Source Management (LSM) with No Insecticide Resistance

“…Pre-experiment con rmed that the appropriate dosage of PACl suspension was 60 ml/L, which means the mass concentration of PACl to water was about 0.6 mg/L. It was normal dosage in water treatment [41,42]. The complete coagulation-occulation operation includes the addition of coagulants and the mixing process, so the experiment was divided into four parallel control groups, group1 ~ 4 (Fig.…”

Multiple use of iron in an urban water system

“…CEPT is done with a combination of iron salts and polymers to further improve solids removal in WWTP (Shewa et al 2020). The enhanced settling can remove approximately 80-90% of the total suspended solids.…”

“…Enhanced sedimentation in CEPT can also lead to insufficient phosphorus in wastewater entering the biological treatment system. However, CEPT does not completely remove the phosphorus in the system (Shewa et al 2020). This can be addressed by the careful design of chemical dosing during CEPT to avoid potential phosphorus limitation in the downstream biological treatment system.…”