Research on the Pricing of Reclaimed Water: a Case Study of a Wastewater Reclamation and Reuse Project

. The reclaimed water produced by sewage treatment plants can be reused for many purposes, which has gradually been paid great attention. However, its pricing mechanism has not been well established especially in China, which has brought certain restrictions on the wide application of reclaimed water. Therefore, this paper attempts to analyze the current situation of domestic reclaimed water pricing, combined with the research and analysis of reclaimed water production costs and related industry profits, and gives the recommended reclaimed water pricing. Taking the reclaimed water reuse project in Ningbo, China as an example, the cost and profit are analyzed by season. The recommended price in non-winter is 0.3833 yuan/ton, and the recommended price in winter is 0.4283 yuan/ton. This study may provide some reference for the improvement of the pricing mechanism of reclaimed water, thus contributing to the wide application of reclaimed water.


Introduction
As a sustainable water resource, reclaimed water can alleviate the water shortage crisis and achieve a virtuous cycle of water ecology [1,2]. As the second water source of the city, reclaimed water produced by sewage treatment plant can be reused for many purposes, including industrial uses [3,4], scenic environment uses (ornamental and recreational purposes) [5], agricultural irrigation [6,7], municipal miscellaneous uses [8] and groundwater recharge [9,10]. However, the pricing mechanism of reclaimed water obtained by advanced treatment or water regeneration process of sewage treatment plant has not been established and perfected, which brings certain restrictions to the wide application of reclaimed water.
Wastewater reclamation and reuse market is still in its infancy in China. Many cities have not really started to use reclaimed water, and there are some difficulties in formulating and implementing the relevant national reclaimed water price policy. For example, since 2008, the price of reclaimed water in Beijing had been maintained at 1 yuan/m 3 , while the price of domestic water for residents was 4 yuan/m 3 , and industrial water was 6.21 yuan/m 3 . Until May 2014, the Beijing Municipal Water Authority set the reclaimed water price as a maximum of no more than 3.5 yuan/m 3 . In 2015, Tianjin divided the use of reclaimed water into three categories: reclaimed water for residents' living, reclaimed water for power generation enterprises and other reclaimed water, and implemented classified prices. Specifically, the water consumption per cubic meter of residential water was adjusted from 1.10 yuan to 2.20 yuan; the water consumption per cubic meter of power generation enterprises was adjusted from 1.50 yuan to 2.50 yuan; other water (including industrial, administrative, business services, car washing, temporary water, etc.) was adjusted to 4.00 yuan per cubic meter.
The determination of reclaimed water's price mainly takes encouraging consumers to use reclaimed water and increasing the price ratio of reclaimed water price to tap water price into considerations. Compared with urban tap water tap water price, reclaimed water price has a strong advantage, as shown in Table 1.

2.Calculation of water reclamation cost in case sewage treatment plant
Based on the field investigation and related data, the operation cost of wastewater reclamation in the case sewage treatment plant is calculated according to the scale of 160,000 tons/day, and the accounting details are as follows.

(1) High efficiency sedimentation tank
The cost mainly includes the cost of civil engineering and equipment, and the cost of ton water is calculated to be 0.0453 yuan/ton. Since the facility is a shared facility for conventional treatment and wastewater reclamation, it is calculated at 50% cost, and the reclaimed water treatment part is converted to 0.02265 yuan/ton.
(2) Filter cloth filter The cost also includes the cost of civil engineering and equipment, and the cost of ton water is calculated to be 0.0351 yuan/ton. Similarly, considering that the facility is a shared facility for conventional treatment and wastewater reclamation, the cost is calculated to be 0.01755 yuan/ton. (

3) Reclaimed water pump room
Similarly, the cost is calculated to be 0.0272 yuan/ton. Therefore, the total depreciation cost of the above three equipment and facilities for reclaimed water treatment is C 1 =0.02265+0.01755+0.0272=0.0674 yuan/ton.

2.2Daily operating costs and expenses
(1) Advanced treatment and reclaimed water treatment operation electricity charges ① The electricity cost required for reclaimed water to be raised to the water replenishment point According to the actual electricity cost estimation of reclaimed water lifting in the northern sewage treatment plant, the reclaimed water volume in the northern area from January to June 2020 is 3476895 tons, the power consumption of the lifting pump is 340007 kwh, and the corresponding cost is 4.09 million yuan.
② Electricity cost for advanced treatment In the No.5 substation of the sewage plant, 60 % of the electricity supply (9700 kWh/d) is required for the deep treatment of all equipment. The cost is similar to the depreciation cost of equipment and facilities, which belongs to the standard discharge and reclaimed water utility fee, so it is recommended to be approved at 50 % each. Therefore, the electricity cost for advanced treatment is 1.52 million yuan.
(2) Equipment replacement and maintenance costs of advanced treatment and reclaimed water treatment facilities ①The annual replacement cost of filter cloth The sum of the cost of filter cloth and labor cost is 3.1 million yuan. Considering that the facility is a shared facility for conventional treatment and wastewater reclamation, the cost is calculated to be 1.55 million yuan. Therefore, C 3 =155÷16÷365=0.0265 yuan/ton.

② Maintenance cost of advanced treatment equipment and reclaimed water lifting pump equipment
The maintenance cost is estimated to be 1300,000 yuan/ year. Since the facility is a shared facility for clean discharge standard treatment and reclaimed water reuse, it is recommended to be calculated at 50% cost, which is 650,000 yuan after approval. Therefore, C 4 =65÷16÷365=0.0111 yuan/ton ③ Water quality testing and instrument maintenance costs Cost for online instrument operation and maintenance, daily monitoring, monthly monitoring, and instrument measurement are about 704,000 yuan. Because the facility is a special facility for reclaimed water reuse, it is recommended to include the full cost into the accounting.
Facilities and equipment instrument replacement and maintenance costs total reclaimed water apportionment costs are calculated as C 5 =(155+65+70.4)÷16÷365=0.0497 yuan/ton (3) Labour cost Due to the need to add two professionals responsible for reclaimed water reuse, it is recommended to be accounted for according to the full cost. Thus, C 6 =36÷16÷365=0.0062 yuan/ton (4) Reagent fee for wastewater reclamation The reagent fee is a special agent for reclaimed water treatment and is approved at full cost. The reagent includes quartz sand, PAC and PAM, which costs 42, 2590 and 544 thousand yuan, respectively. Thus, C 7 =(4.2+259+54.4)÷16÷365=0.0544 yuan/ton (5) Cost of pipeline continuous disinfectant Since the reclaimed water is replenished into urban surface rivers, considering the limited length of reclaimed water supply pipelines, it is recommended that the dosage should not exceed 3.0 mg/L (accounted by active chlorine). The active chlorine content of sodium hypochlorite solution is 10%, and the usage is 1752 tons/year (calculated as 160,000 tons). The average market price of sodium hypochlorite is 700 yuan/ton. The cost is 1.2264 million yuan. Therefore, C 8 =122.64÷16÷365=0.021 yuan/ton.

(6) Cost of ammonia nitrogen removal agent in winter
According to the local temperature conditions of the project in the past years, only in December, January and February of each year, the monthly average temperature is less than 10 degrees Celsius, which is not conducive to biological denitrification. Therefore, the approved low temperature days are 90 days, and the average price of sodium hypochlorite is 700 yuan/ton. Approved postprocessing cost is 221.76 million yuan. Therefore, C 9 =221.76÷16÷365=0.0380 yuan/ton (The cost is incurred only in winter and 0 in summer).

3.Analysis of average profit of reclaimed water reuse
The main water treatment related business, income and profit of many water enterprises in recent years are analyzed as shown in Table 2. Sewage treatment, seawater desalination, civil water purification, wetland protection and reconstruction, river comprehensive management, etc.
In terms of operating income, sewage treatment business accounts for more than 85 % of the total.

Business characteristics
Sewage and reclaimed water treatment business accounted for 19 % of the main business, while revenue accounted for 31% of net profit.
Domestic sewage treatment leading enterprises with MBR membrane technology as the core technology.
One of the earliest enterprises engaged in industrial wastewater treatment in China mainly adopts conventional activated sludge process.

Income About HK $ 25 billion
About 12 billion yuan in total (water treatment revenue of about 8 billion yuan) About 4 billion yuan in total (water treatment revenue of about 3.8 billion yuan) Profit Gross-profit ratio is about 30%. Gross-profit ratio is about 30%. Gross-profit ratio is about 27%.
In summary, the profit of reclaimed water production is set at 20% according to the average profit rate of the industry.

4.Seasonal recommended price for the case reclaimed water reuse project
Interceptor combined flow drainage system, if set up unreasonably, often affects the operation of the entire pipe network system and reduces the water quality of sewage treatment plant influent, thus affecting the effect of water environment management. The following is a brief introduction to the more prominent common problems that exist in traditional interceptor pipes. According to the comprehensive analysis, the seasonal recommended price and cost of the case reclaimed water reuse project are shown in Table 3.
The non-winter recommended water supply price is C annual price =0.3193+0.064=0.3833 yuan/ton. The winter recommended water supply price is C winter price =0.3573+0.071=0.4283 yuan/ton

5.Conclusions
This paper analysed the current situation of pricing of reclaimed water and tap water in typical cities in China. In view of the imperfect price mechanism, a reclaimed water reuse project in Ningbo is taken as a case to analyse the cost of reclaimed water production in the case sewage treatment plant. Combined with the investigation and analysis of the profit of water treatment business of typical enterprises in the industry, the suitable recommended price is given. The recommended price in non-winter is 0.3833 yuan/ton, and the recommended price in winter is 0.4283 yuan/ton. Based on the analysis of the actual cost of the project and the relatively reasonable profit in the industry, the pricing method and the recommended price are suitable for the pricing of reclaimed water in similar projects and may also provide reference for subsequent research and engineering application.