Costs Of Wastewater Treatment Plants Research Articles

Estimating capital costs of wastewater treatment plants at the strategical level

ABSTRACTThe present paper aims at the establishment and testing of construction cost functions for wastewater treatment plants (WWTP) based on their hydraulic and physical characteristics. A five-step methodology is followed: (1) database construction and asset characterization; (2) present cost value calculation; (3) key parameters and cost functions establishment; (4) cost modelling; and (5) model testing. A large set of construction costs and infrastructure data from several Portuguese wastewater utilities is analysed including 147 WWTP. Simple linear regression analysis is carried out to obtain cost functions for five types of WWTP. The cost modelling also includes the estimation of 90% prediction bands. Each developed cost function is tested for checking their statistical significance. Results allow the estimation of capital costs of new WWTP and the assessment of the current value of existing assets at the strategical and tactical planning levels without the knowledge of the specific components of the facilities.

English

Water and Wastewater treatment plants requires huge amount of energy operation cost. As per the energy demand, water companies require cost reducing and sustainable solution to produce energy. The generated energy should reduce its dependence on fossil fuel. For this study, different types of hydropower technology have been studied. And as per suitable criteria of wastewater treatment plants, Gravitational water vortex flow power plant which is one of the best low head and low flow rate based hydropower technology have been selected. To determine optimum efficiency of power plant, a lab scale model will be prepared for selected hydropower technology. Generated electricity will be considered for co2 reduction energy and it can use in plant itself which can reduce its cost. Parameters of wastewater will be check for selection of appropriate turbine blade materials. This will be an innovative approach which can reduce the energy cost of wastewater treatment plants.

Energy Efficiency Drivers in Wastewater Treatment Plants: A Double Bootstrap DEA Analysis

The relevance of wastewater treatment service has increased in recent years, since it has a significant impact on the natural environment. A treatment plant facilitates energy generation, the recovery of products from waste, and the reuse of wastewater for industrial and irrigation purposes. An indirect environmental effect is the high energy consumption for pumping water and for tank aeration. The objective of this research is to develop a tool for measuring the energy costs of wastewater treatment plants and identifying how they can be reduced. The method adopted is double-bootstrap data envelopment analysis. The results show that the variables with a significant influence on efficiency are the chemical oxygen demand concentration; plant capacity; rate of used capacity, which positively affects efficiency; weight of industrial customers, which exerts a negative impact; and aeration system, with a negative impact for turbines. This paper suggests the adoption of an effective control tool to monitor the costs drivers and energy expenditure of water utilities.

AIR DISPERSION MODELLING AND SIMULATION IN AERATION TANKS

The necessary oxygen concentration for the biological process depends on the organic matter present in wastewater characterized by organic matter reaction rate with oxygen, k. This article highlights the impact of the reaction coefficient on oxygen dispersion in water. The first stage of the research led to the determination of the ratio between the coefficient of reaction and the coefficient of dispersion on the vertical of the tank as k/ez . [0.066 - 0.79]. Starting from this ratio, the specific oxygen flow required for the aeration process was determined to obtain a minimum oxygen concentration of 2 mg/L in the bottom zone of the tank: for k=3, specific gas flow qg=1.37 [m3/s*m], for k=0.2, qg=0.77 [m3/s*m] and for k=1.5, qg=1.03 [m3/s*m]. Value of gas flow rate has an important impact on reduction of the costs of wastewater treatment plants. This value has an important impact on the reduction of costs for wastewater treatment plants.

An evaluation of operation and maintenance costs of wastewater treatment plants: Gebze wastewater treatment plant sample

An evaluation of operation and maintenance costs of wastewater treatment plants: Gebze wastewater treatment plant sample

Sustainable operation of a biological wastewater treatment plant

The sustainable operation of a biological wastewater treatment plant is significantly linked to its removal efficiency, cost of sludge management, energy consumption and monitoring cost. The biological treatment offers high organic removal efficiency, it also entails significant sludge production, which contains active (live) and inactive (dead) microorganisms and must be treated prior to final disposal, in order to prevent adverse impact on public health and environment. The efficiency of the activated sludge treatment process is correlated to an efficient solid-liquid separation, which is strongly depended on the biomass settling properties. The most commonly encountered settling problems in a wastewater treatment plant, which are usually associated with operating conditions and specific microorganisms growth, are sludge bulking, floating sludge, pin point flocs and straggler flocs. Sustainable management of sludge and less energy consumption are the two principal aspects that determine the operational cost of wastewater treatment plants. Sludge treatment and management accumulate more than 50% of the operating cost. Aerobic wastewater treatment plants have high energy requirements for covering the needs of aeration and recirculations. In order to ensure wastewater treatment plants’ effective operation, a large number of physicochemical parameters have to be monitored, thus further increasing the operational cost. As the operational parameters are linked to microbial population, a practical way of wastewater treatment plants’ controlling is the microscopic examination of sludge, which is proved to be an important tool for evaluating plants’ performance and assessing possible problems and symptoms. This study presents a biological wastewater treatment plant with almost zero biomass production, less energy consumption and a practical way for operation control through microbial manipulation and microscopic examination.

Energy consumption and economic cost of typical wastewater treatment systems in Shenzhen, China

Wastewater treatment, a great potential alternative to alleviate water shortage, has been attached more and more importance in China, and has been developing very fast. The quantity of wastewater treatment plants in China has increased up to 3272 in June 2013, and has a total handling capacity of 0.14 billion t/day. However, wastewater treatment requires to consuming a lot of energy, and even energy consumption is often the main operation cost of wastewater treatment systems. Thus, it is very necessary to explore energy consumption of wastewater treatment systems and its influential factors, and seek for some possible pathways to save energy and lower cost. In this paper, we investigated the average energy consumption per unit wastewater treatment in Shenzhen, and analyzed the effect of treatment capacity and treatment technology on the energy cost per unit of wastewater treatment. The results showed that the average energy consumption of wastewater treatment plants in Shenzhen was about 0.20 ± 0.06 kWh/t, much less than those in some developed countries. This result may be related to the advanced wastewater treatment plants newly constructed and the low water quality requirements of wastewater treatment in Shenzhen. As the key to wastewater treatment, biochemical treatment sub-process consumed 50–70% of total energy cost in wastewater treatment. Secondly, the larger the treat capacity, the lower the energy cost per unit of wastewater treatment was. And the difference of treatment technologies can also significantly affect the energy consumption per unit of wastewater treatment. Finally, labor cost and electricity consumption respectively covered about 30.1% and 26.3% of total economic cost in the three typical wastewater treatment plants in original Shenzhen. Thus, upgrading treatment machines & equipment and improving management level are two effective alternatives to decrease energy consumption and lower total economic cost of wastewater treatment plants in Shenzhen and even China.

PI and Fuzzy Control for P-removal in Wastewater Treatment Plant

Due to the complex and non linear character, wastewater treatment process is difficult to be controlled. The demand for removing the pollutant, especially for nitrogen (N) and phosphorus (P), as well as reducing the cost of wastewater treatment plant is an important research theme recently. Thus, in this paper, the benchmark proposed default control strategy and 10 additional control strategies are applied on the combined biological P and N removal Benchmark Simulation Model No.1 (BSM1-P). In addition, according to the results of applying PI controllers, as usual, we also chose the group with the better performance, as well as the default control strategy, to replace the PI controllers with fuzzy controllers. In this way, it can be seen that in all cases the quality of effluent of the controlled process could be improved in some degree; and the fuzzy controllers get a better phosphorus removal.

SIMULTANEOUS CARBON AND NUTRIENT REMOVAL FROM DAIRY WASTEWATER IN SEQUENCING BATCH REACTOR (SBR)

<div> <p>Sequencing batch reactor (SBR) is a time-oriented wastewater treatment (WWT) system in a single reactor with flow and energy input according to the predetermined operational cycle time. The treatment efficiency of SBR varies with the duration of the cycle time, which affects the reactor size and hence the cost of WWT plant. This paper presents an experimental study in a bench scale SBR model with a working volume of 15 L with an onjective to determine  the optimum cycle time for simultaneous removal of carbon and nutrient from the dairy wastewater. Using the equalized dairy wastewater experiments with four cycle times of 8 h, 6 h, 4 h and 2 h were conducted and the effluent concentrations were compared to the effluent standards. In conclusion, the data suggest the SBR process with 6 h cycle time as the optimum cycle time for treating dairy wastewater for simultaneous carbon and nutrient removal.</p> </div> <p> </p>

Simulation of the Anaerobic Digestion of Microwave Pre-Treated Waste Activated Sludge with ADM1

AbstractThe disposal of sludge originating from municipal waste water treatment is a major issue and represents up to 50% of the operating costs of wastewater treatment plants (WWTP). (Appels et al., 2008) This sludge, a by-product of the treatment processes, however, has the potential to be converted into an energy rich biogas, i.e. a mixture of ca. 65% CH4 and 35% CO2, which can be utilized for the sustainable production of heat and/or electricity. Various pre-treatment methods have been suggested in literature for improving the solids reduction and biogas production rate by enhancing the digestion's rate limiting step, i.e. organic matter hydrolysis. They all induce the solubilization of complex particulate matter so this is more rapidly and completely consumed during the anaerobic digestion process. Methods that have been shown to have a positive effect on anaerobic digestion include chemical, mechanical, biological and thermal processes. Microwave disintegration is one of the more recently applied pre-treatment methods. The disintegration is caused by the combination of thermal and athermal effects and may hence provide superior results compared to a heat treatment (Eskicioglu et al., 2007).The application of mathematical models for the optimization of the digestion process is widely acknowledged. Due to the complexity of the microbial process, accurate modelling of anaerobic digestion is, however, a daunting task. A major stride countering this problem was achieved by the development of the Anaerobic Digestion Model no 1 (ADM1) by the corresponding IWA task group (Batstone et al. 2002). This model is ever since, considered to be the state of the art in modelling of anaerobic digestion and has been the platform for further refinements and numerous applications (Batstone et al. 2006).The main aim of this work is to investigate the ability of ADM1 to describe anaerobic digestion of microwave pre-treated sludge. Compared to untreated sludge, the composition and structure of the sludge is changed dramatically due to the treatment. The recorded data and digester performances were compared with the results of a modelling in ADM1 (Batstone et al., 2002). Practically, the ADM1 implementation as described by Rosen & Jeppsson (Rosen and Jeppsson (2005)) is chosen as it effectively completes the mass balance for COD, carbon and nitrogen.

Effect of High-Temperature Microwave Irradiation on Municipal Thickened Waste Activated Sludge Solubilization

Sludge digestion and stabilization governs almost half of the operating cost of wastewater treatment plants, and hydrolysis is the limiting step in sludge digestion. Increasing hydrolysis by implementing pretreatment prior to digestion can increase the digestion efficiency. Among pretreatment methods, thermal pretreatment at temperatures around 160–175°C tends to produce better solubilization. Microwave (MW) pretreatment was recently studied as an alternative method to conventional thermal pretreatment. Until now, MW pretreatment above boiling point had not been studied for sludge solubilization and digestion. This paper provides preliminary results on the effect of MW pretreatment operating conditions such as high temperature (T) (110–175°C), MW intensity (I) (1.25 and 3.75°C/min), and sludge concentration (C) (6 and 11.85%) on solubilization. From experimental results and three-factor fixed-effect analysis of variance (ANOVA) determination it was found that T, I, and C main effects and T:I and T:C interactions as well as T:I:C interaction are significant at a 94% confidence interval.

Comparison of four chemical uncouplers for excess sludge reduction

A substantial part of the operating costs of wastewater treatment plants (WWTP) is associated with the management and treatment of the excess sludge generated during the treatment process. Different strategies have been applied for excess sludge reduction, such as the oxic‐settling‐anaerobic process, the high dissolved oxygen process, the uncoupler‐containing activated sludge process, the ozonation‐combined activated sludge process, control of sludge retention time and biodegradation of sludge in a membrane‐assisted reactor. Chemical uncouplers have been shown to reduce excess sludge production, disassociating the energy coupling between catabolism and anabolism. These metabolic uncouplers may be organic compounds, such as 2,4‐dinitrophenol (2,4‐DNP) or 3,3′,4′,5‐tetrachlorosalicylanilide (TCS), or heavy metals. In this paper, four different chemicals (2,4‐DNP, TCS, copper (Cu) and zinc (Zn)) were chosen for short‐term tests for studying their ability to reduce sludge yield (Yx/s ) and, consequently, their potential for reducing excess sludge production. According to the results obtained, only TCS seems to be very effective in reducing sludge production from the activated sludge process. Compared with the control test, Yx/s can be reduced by over 30% at 0.8 mg/l TCS. It was also found that the substrate removal capability was not adversely affected by the presence of TCS. Furthermore, an increase in the microbial activity of the system was observed.

Optimal design of wastewater treatment plant using adaptive simulated annealing

This paper deals with the application of Adaptive Simulated Annealing (ASA) for the optimal design of the wastewater treatment plant. The plant consists of a trickling filter, an activated sludge aeration vessel and a secondary clarifier. In this work a successful attempt has been made to use the ASA for optimal design of wastewater treatment plant. ASA based optimal design values have been compared with conventional optimization approaches and has been found to yield the lowest total construction cost of wastewater treatment plant. From this work, it has been found that artificial intelligence based optimization techniques such as adaptive simulated annealing is found to be suitable for the optimal design of wastewater treatment plant. Journal of Applied Sciences and Environmental Management Vol. 9(1) 2005: 107-113

Identifying causes for N 2O accumulation in a lab-scale sequencing batch reactor performing simultaneous nitrification, denitrification and phosphorus removal

The recently described process of simultaneous nitrification, denitrification and phosphorus removal (SNDPR) has a great potential to save capital and operating costs for wastewater treatment plants. However, the presence of glycogen-accumulating organisms (GAOs) and the accumulation of nitrous oxide (N 2O) can severely compromise the advantages of this process. In this study, these two issues were investigated using a lab-scale sequencing batch reactor performing SNDPR over a 5-month period. The reactor was highly enriched in polyphosphate-accumulating organisms (PAOs) and GAOs representing around 70% of the total microbial community. PAOs were the dominant population at all times and their abundance increased, while GAOs population decreased over the study period. Anoxic batch tests demonstrated that GAOs rather than denitrifying PAOs were responsible for denitrification. N 2O accumulated from denitrification and more than half of the nitrogen supplied in a reactor cycle was released into the atmosphere as N 2O. After mixing SNDPR sludge with other denitrifying sludge, N 2O present in the bulk liquid was reduced immediately if external carbon was added. We therefore suggest that the N 2O accumulation observed in the SNDPR reactor is an artefact of the low microbial diversity facilitated by the use of synthetic wastewater with only a single carbon source.

Overinvestment When Allocating Costs of Wastewater Treatment Plant

There is a potential for overinvestment of resources into flow reduction when two cities jointly own a wastewater treatment plant. One city can shift more of the plant's total fixed cost onto the other city if it reduces its share of the wastewater flow into the sanitary system. Each city has an incentive to reduce its flow of groundwater infiltration and storm runoff into its sanitary system as long as the additional repair cost of doing so is less than the reduction in its total variable (treatment) cost plus the reduction in its fixed cost payment.

Optimal policies for activated sludge treatment systems with multi effluent stream generation

Most industrial processes generate liquid waste, which requires treatment prior to disposal. These processes are divided into sectors that generate effluents with time dependent characteristics. Each sector sends the effluent to wastewater treatment plants through pumping-stations. In general, activated sludge is the most suitable treatment and consists of equalization, aeration and settling tanks. During the treatment, there is an increase in the mass of microorganisms, which needs to be removed. Sludge removal represents the major operating costs for wastewater treatment plants. The objective of this work is to propose an optimization model to minimize sludge generation using a superstructure in which the streams from pumping-stations can be sent to the equalization tank. In addition, the aeration tank is divided into cells that can be fed in series and parallel. The model relies on mass balances, kinetic equations, and the resulting Nonlinear Programming problem generates the best operational strategy for the system feed streams with a high substrate removal. Reductions of up to 30 % can be achieved with the proposed strategy maintened BOD efficiency removal upper than 98 %.

Oxidation-Ditch Process Using Falling Water as Aerator

This paper examines the use of falling water as an aerator for the oxidation-ditch process. The study was carried out in order to clarify the characteristics of this process and compare it with other oxidation-ditch processes. The method uses pumps that lift wastewater and cause it to develop a head, creating a cascade or waterfall. Application of this concept may reduce construction costs for wastewater treatment plants. Furthermore, nitrogen removal is made easier through simple control of pump speed, on-off functions, and change in the height of the waterfall. Aeration efficiency is similar to that of aerators used in other oxidation-ditch processes. The power input of this oxidation-ditch-aeration process was the lowest of all the oxidation-ditch processes. This oxidation-ditch process also provides various other advantages for waste-treatment plants.

Estimation of wastewater treatment costs: Evaluation of the CAPDET model for Canadian conditions

CAPDET is a computer program for estimating construction and operation costs of wastewater treatment plants. A validation study of the model was carried out in order to assess its capabilities for predicting these costs for Canadian conditions. The validation was performed using data from existing full-scale facilities located in Ontario, Québec, and other provinces. The validation study identifies problems in applying the model to Canadian conditions and formulates precise recommendations to account for them. Key results of the validation study were that construction costs can be predicted by the model to within ±20% of the actual costs and operation and maintenance costs to within ±30%. Key words: wastewater treatment plants, construction costs, operation and maintenance costs, CAPDET, computer program.

Variable operating costs of wastewater treatment plants

In this paper, variable operation of the plant is studied through a model previously developed for simulating steady-states and optimising the total design cost of a treatment plant. In particular, various possible designs of a plant are considered; for each of them, a set of steady-state values for the effluent quality level, compatible with the initial design, are simulated and the total variable operating costs are optimised. In this way the dependence of the variable operating costs on both the design and operating effluent quality levels can be analysed.

Impact of Regulatory Delays on the Cost of Wastewater Treatment Plants

The Environmental Protection Agency's (EPA) Wastewater Treatment Plant Construction Grants Program has come under attack from persons involved in the administration of the program, as well as from members of municipal authorities that have received these grants. It is believed that the requirements mandated by the EPA for projects receiving grants cause so much time to elapse before construction bids can be accepted, that the increase in costs due to inflation outweighs the decrease in costs to the municipality from receiving an EPA grant. Thus, the effectiveness of this program in reducing the financial burden to a community of building a wastewater treatment plant is questioned. However, to properly assess the effect of delays, the time preference factor for money and the change in cash flow to build and operate a treatment plant need to be recognized. These will affect how the community views, i.e., values, the required outflow of funds. The objective of this study is to evaluate the effects of time lags of various lengths on the present value of the future outflow of funds to pay for and operate treatment plants.