Jining Chen

Operational energy performance assessment system of municipal wastewater treatment plants

Based on the statistical analysis of operational energy consumption and its influential factors from data of 599 Chinese WWTPs in 2006, it is noticed that the most influential factors include treatment technology adopted, treated sewage amount, removed pollutants amount, etc. Using the conclusion above, this paper sets up an integrated system of operational energy performance assessment for municipal wastewater treatment plants. Combining with result from on-spot research and model simulation, the calculating method of benchmark value and score of 7 energy efficiency indicators grouped into 3 levels is stated. Applying the assessment system to three plants, its applicability and objectivity are proved and suggestions to improve energy performance are provided.

Development and identification of an integrated waterworks model for trihalomethanes simulation

To evaluate the impact that new trihalomethanes (THMs) regulations will have on the performance of conventional waterworks in China, we developed an integrated waterworks model to simulate the dynamic behavior of THMs and other associated components, e.g. organic matter, ammonia, and residual chlorine, throughout the conventional water treatment process, which included pre-chlorination, coagulation-flocculation, sedimentation, filtration and post-chlorination. A comprehensive kinetic scheme that takes into account both the physical and biological mechanisms involved in the water treatment processes and the chemical reactions that result from chlorination was proposed for model conceptualization. In addition, the Petersen matrix was designed to present the model and formulate the mass balance equations for the model variables. The model was then identified using the Hornberger-Spear-Young (HSY) algorithm and tested against field data from the Qingzhou Waterworks in Macao, China. Despite gross uncertainty associated with the field data, the model could generally provide good predictions of the simulated variables and meet the management purposes. Furthermore, the identified model parameters agreed well with values that were reported in the literature and could be reasonably interpreted.

Integrated assessment of urban drainage system under the framework of uncertainty analysis

Due to a rapid urbanization as well as the presence of large number of aging urban infrastructures in China, the urban drainage system is facing a dual pressure of construction and renovation nationwide. This leads to the need for an integrated assessment when an urban drainage system is under planning or re-design. In this paper, an integrated assessment methodology is proposed based upon the approaches of analytic hierarchy process (AHP), uncertainty analysis, mathematical simulation of urban drainage system and fuzzy assessment. To illustrate this methodology, a case study in Shenzhen City of south China has been implemented to evaluate and compare two different urban drainage system renovation plans, i.e., the distributed plan and the centralized plan. By comparing their water quality impacts, ecological impacts, technological feasibility and economic costs, the integrated performance of the distributed plan is found to be both better and robust. The proposed methodology is also found to be both effective and practical.

CO2 Emission Reduction Efforts Made by China's Electricity Sector and the International Comparison

Starting from the misunderstanding that China is doing little in controlling her greenhouse gas emissions along with the rapid economic growth, this paper tried to break this myth by looking into China’s electricity sector. It is found out that from 2000 to 2007, this sector was having great improvements in energy efficiency improvements, in demand side management and in reducing transmission losses and electricity consumed by power plants, ranked by their contributions to the overall sectoral emission reductions. The cumulative emission reductions from 2000 to 2007 amounted to 553 million tons, which means the unilateral emission reduction actions from China’s electricity sector alone helped the world exempt from a one-year national emission from a country as economically-powerful as United Kingdom. Other comparisons in generating efficiency side have been made between China and US. One suggestion for future work has been given at the end of the paper.

Retrofitting conventional primary clarifiers to activated primary clarifiers to enhance nutrient removal and energy conservation in WWTPs in Beijing, China.

Biological nutrient removal requires sufficient carbon source. Meanwhile, the removal of organic matter in wastewater requires energy consumption in the aeration tank. Carbon source for nutrient removal in most wastewater treatment plants with conventional primary clarifier (CPC) is generally insufficient in China. In order to increase carbon source and to save energy, a part of the CPC may be retrofitted as an activated primary clarifier (APC). In this paper, a pilot scale experiment was conducted to examine the performance of primary sludge fermentation and its effect on nitrogen and phosphorus removal. Results show that the primary sludge fermentation in APC has produced a similar VFA/TP ratio but a higher BOD5/TN ratio compared with those in the CPC effluent, and the TN concentrations in the secondary effluent are at 8.0, 10.8, and 17.4 mg/L, while TP is at 0.45, 1.10, and 2.28 mg/L when the pilot test system was fed with (1) the APC effluent, (2) 50% from the APC effluent and 50% from the CPC effluent, and (3) the CPC effluent, respectively. Results also indicate that the BOD5/TN ratio is a more sensitive factor than the VFA/TP ratio for nutrient removal and energy conservation for the APC fermentation.This paper reports on a pilot trial of a novel MBR developed with coarse-pore membrane module by the authors. The plant was operated for 370 days with up to 7 m(3)/d raw saline sewage after 3-mm screening. The plant performed successfully without membrane fouling for 270 days except an accidental power source failure for 30 h, during which membrane was fouled under no aeration and mixing condition. EPS increases in both the reactor and the bio-cake on the membrane surface explained this fouling. The average TSS, COD and TKN removal efficiency were 92, 90, and 93%, respectively, under a high effective permeate flux of 4.8 m/d and a low air-to-water ratio of 15.Over the past decade, the concept of anaerobic processes for the treatment of low temperature domestic wastewater has been introduced. This paper uses a developed wastewater flowsheet model and experimental data from several pilot scale studies to establish the impact of integrating anaerobic process into the wastewater flowsheet. The results demonstrate that, by integrating an expanded granular sludge blanket reactor to treat settled wastewater upstream of the activated sludge process, an immediate reduction in imported electricity of 62.5% may be achieved for a treated flow of c. 10,000 m(3) d(-1). This proposed modification to the flowsheet offers potential synergies with novel unit processes including physico-chemical ammonia removal and dissolved methane recovery. Incorporating either of these unit operations can potentially further improve the flowsheet net energy balance to between +0.037 and +0.078 kWh m(-3) of produced water. The impact of these secondary unit operations is significant as it is this contribution to the net energy balance that facilitates the shift from energy negative to energy positive wastewater treatment.Pseudomonas sp. strain DY1 was newly isolated from soil with rotten wood and identified as a member of the genus Pseudomonas based on 16S rDNA and biochemical tests. Acid Black 172, a water soluble Cr-complex dye, was then selected as a model dye to investigate the decolorisation ability of the strain. It was observed that the growth of the strain was not inhibited by high dose of metal ions (10 mM), and efficient decolorisation was still observed when high concentrations of Fe(2+), Fe(3+) and Ca(2+) existed. The optimal decolorising conditions obtained from Taguchi design were as follows: temperature 37˚C, pH 7.0, Fe(3+) and proline concentrations of 7 mM and 3.0 g/L, respectively. Under the optimal conditions, 94.5% of Acid Black 172 (100 mg/L) could be decolorised by the strain in 24 h. The kinetics of the decolorisation best fitted the first order kinetic model (R(2)=0.981). Besides, the phytotoxicity study demonstrated a good detoxification by the strain. This work has a certain practical value in microbial decolorisation of textile wastewater.

Risk-Based Water Quality Management in River System

Presence of uncertainties and varieties in the model input variables and parameters is one major challenge in the river water quality management practice. A risk-based framework is developed to address the problems derived from uncertainties and varieties in the river water quality management work and assess the performance risk of waste load allocation strategies in compliance with the water quality management goal. Monte Carlo simulation technique is applied to take the different uncertainties into account. Regional sensitivity analysis using a task-based Hornberger-Spear-Young (HSY) algorithm is conducted to identify the sensitive point sources, sort them according to their sensitivities and produce available strategies of waste load allocation for the pollution sources.