Sewage pre-concentration for maximum recovery and reuse at decentralized level

Abstract

Pre-concentration of municipal wastewater by chemically enhanced primary treatment (CEPT) was studied under controlled laboratory conditions. Both iron and aluminium-based coagulants were examined at gradually increasing concentrations (0.23, 0.35, 0.70 and 1.05 mmol/L). The CEPT sludge generated from different coagulation experiments was digested in batch anaerobic reactors, while the supernatant was tested in a dead-end microfiltration setup. The results of the study show that biogas yield was dramatically decreased (from 0.40 to 0.10 m(3)/kg chemical oxygen demand of influent) with increasing coagulant dose. In contrast, supernatant filterability was improved. Based on the laboratory results, a conceptual design was produced for a community of 2000 inhabitant equivalents (IE), using CEPT technology (at low coagulant dose) with anaerobic digestion of the concentrates. According to this, the capital and operational costs were 0.11 and 0.09 €/m(3), respectively. The biogas generated is used for digester heating and the overall process is energy self-sufficient. At a small-scale and in private applications, CEPT technology is preferably operated at higher coagulant dose, followed by membrane filtration for water reuse. Accordingly, sewage purification and reuse is possible without implementing aerobic biological processes.

A Stochastic Model to Predict Flow, Nutrient and Temperature Changes in a Sewer under Water Conservation Scenarios

“…The concentration of dissolved pollutants and suspended sediment at every node in the sewer network is calculated for every time step using the InfoWorks ® Network Model. The governing equation at a node is given by conservation of mass, Equation (1). Pollutant inflows arrive from incoming conduits and any external sources, in this case, wastewater events (household discharges).…”

“…Resource recovery from wastewater is more effective at high concentrations. This can be achieved through dewatering processes at treatment plants [1][2][3] but another option is to limit wastewater dilution in the collection process [4]. Limiting wastewater dilution can be achieved by reducing domestic drinking water use, separation of storm/wastewater systems and preventing groundwater inflow by repairing/replacing broken pipes.…”

Approaches to energy and resource recovery from municipal wastewater

“…Evidence suggested that the operating and maintenance costs of CEPT were higher than those of conventional primary treatment (Chagnon & Harleman, 2002), e.g. the operating costs of CEPT increased by about €0.06-0.10/m 3 wastewater treated, equivalent to €0.24-0.40/kg COD due to the use of chemicals (Diamantis et al, 2013). Moreover, the higher dosage of chemicals, especially at concentrations higher than 100 mg/L for iron or alum, might compromise the biogas productivity in the subsequent AD process.…”

Integrated A-B processes for municipal wastewater treatment

“…It has also been reported, in a WWTP in Mexico, that an annual operational cost of US$ 4 million was incurred due to CEPT with a mean treatment capacity of 4.49 × 10 5 m 3 /day, equivalent to US$ 0.024/m 3 wastewater (Harleman et al, 2002). In addition, the cost associated with CEPT was estimated to be about 0.1 €/m 3 in a wastewater treatment facility with a capacity of 500 m 3 /d where both alum and polymer were used (Diamantis et al, 2013). However, it should be noted that an increased amount of sludge is generated during CEPT, e.g.…”