Compact wastewater treatment process based on abiotic nitrogen management achieved high-rate and facile pollutants removal

A practical study on the near-zero discharge of rainwater and the collaborative treatment and regeneration of rainwater and sewage

Non-conventional water recovery, recycling, and reuse have been considered imperative approaches to addressing water scarcity in China. The objective of this study was to evaluate the technical and economic feasibility of Water Reclamation Plants (WRP) based on an anaerobic-anoxic-oxic membrane bioreactor (A2O-MBR) system for unconventional water resource treatment and reuse in towns (domestic sewage and rainwater). Rainwater is collected and stored in the rainwater reservoir through the rainwater pipe network, and then transported to the WRP for treatment and reuse through the rainwater reuse pumping station during the peak water demand period. During a year of operation and evaluation process, a total of 610,000 cubic meters of rainwater were reused, accounting for 10.4 % of the treated wastewater. In the A2O-MBR operation, the average effluent concentrations for COD (chemical oxygen demand), NH4+-N (ammonium), TN (total nitrogen), and TP (total phosphorus) were 14.23 ± 4.07 mg/L, 0.22 ± 0.26 mg/L, 11.97 ± 1.54 mg/L, and 0.13 ± 0.09 mg/L, respectively. The effluent quality met standards suitable for reuse in industrial cooling water or for direct discharge. The WRP demonstrates a positive financial outlook, with total capital and operating costs totaling 0.16 $/m3. A comprehensive cost-benefit analysis indicates a positive net present value for the WRP, and the estimated annualized net profit is 0.024 $/m3. This research has achieved near-zero discharge of wastewater and effective allocation of rainwater resources across time and space.

Landfill leachate treatment with a full-scale membrane bioreactor: impact of leachate characteristics on filamentous bacteria

Bulking and foaming are extreme filamentous bacterial growths that present serious challenges for the biological leachate treatment process. The current study evaluates the performance of long-term full-scale membrane bioreactor (MBR) treating landfill leachate, specifically focusing on filamentous bacteria overgrowth in the bioreactors. The influence of the variation in leachate structure and operational conditions on floc morphology and filamentous bacteria overgrowth were analyzed for 11 months of operation of the full-scale MBR system. The average chemical oxygen demand (COD) and NH4-N removal efficiencies of the system were 87.8 ± 4% and 99.5 ± 0.7%. However, incomplete denitrification was observed when the F/M ratio was low. The high C/N ratio was observed to enhance the frequency of small flocs. Furthermore, a poor to medium diversity of the microbial community was observed. Haliscomenobacter hydrossis, Microthrix parvicella, and Type 021N were found as the most numerous filamentous organisms. Paramecium spp., Euplotes spp., and Aspidisca spp. were found in small quantities. The limited concentration of PO4-P in the leachate compared to high COD and NH4-N concentrations most probably caused phosphate deprivation and increased abundance of identified filamentous microorganisms. This work is the first study in Türkiye that investigates the bulking and foaming problem in full-scale MBR that treats landfill leachate. Hence, it may provide some pioneering perspectives into landfill leachate remediation by monitoring the hybrid biological system.

Under-loaded operation of an anaerobic-anoxic-aerobic system in dry and wet weather dynamics to prevent overflow pollution: Impacts on process performance and microbial community

Effects of low hydraulic loading rate (HLR) in dry weather and high HLR in wet weather on pollutant removal, microbial community, and sludge properties of a full-scale wastewater treatment plant (WWTP) were extensively studied to explore the risk of under-loaded operation for overflow pollution control. Long-term low HLR operation had an insignificant effect on the pollutant removal performance of the full-scale WWTP, and the system could withstand high-load shocks in wet weather. Low HLR resulted in higher oxygen and nitrate uptake rate due to the storage mechanism under the alternating feast/famine condition, and lower nitrifying rate. Low HLR operation enlarged particle size, deteriorated floc aggregation and sludge settleability, and reduced sludge viscosity due to the overgrowth of filamentous bacteria and inhibition of floc-forming bacteria. The remarkable increase in Thuricola and the contract morphology of Vorticella in microfauna observation confirmed the risk of flocs disintegration in low HLR operation.

Enhanced nutrient removal from stormwater runoff by a compact on-site treatment system

Efficient and space-saving technologies for on-site treatment of stormwater runoff are required to control water pollution in the urban surface. The intermittent nature of stormwater runoff and extremely limited land available greatly hindered the application of current wastewater treatment technologies, and thus synchronous removal of multiple contaminants (especially for nutrient) efficiently was failed by current processes. In this study, a new compact CFFA treatment system, consisting of coagulation, flocculation, filtration and ammonium ion exchange units, was constructed for on-site treatment of stormwater runoff based on batch test optimization and pilot-scale test verification. The coagulation process effectively aggregated particles and precipitated phosphorus by dosing Al₂(SO₄)₃, while flocculation using anionic polyacrylamide further enlarged particle size for efficient micromesh filtration. The dynamic micromesh filtration obtained turbidity and phosphorus removal efficiencies comparable to 30 min gravity settling with greatly smaller footprint. Ion exchange by zeolite showed higher exchange capacity owing to lower initial ammonium nitrogen concentration in the stormwater runoff. The pilot-scale experiments with treatment capacity of 1 L/s showed that the CFFA treatment system achieved synchronous removal of particles (97.2%), nitrogen (79.7%), phosphorus (95.0%) and organic matters (83.3%) efficiently within short hydraulic retention time of 0.35 h, yielding effluent with chemical oxygen demand, suspended solids, total phosphorus and total nitrogen of 38.7, 7.80, 0.22 and 2.80 mg/L, respectively. The CFFA treatment system had the highest pollutant removal loads compared to reported runoff treatment processes in literatures, and was well suited to on-site treatment of stormwater runoff with high space utilization efficiency.