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任務(wù)書
一、原始依據(jù)（包括設(shè)計(jì)或論文的工作基礎(chǔ)、研究條件、應(yīng)用環(huán)境、工作目的等。）
工作基礎(chǔ)：
本畢業(yè)設(shè)計(jì)是對某一給水處理工程的模擬，通過設(shè)計(jì)，使學(xué)生系統(tǒng)的熟悉和掌握環(huán)境工程專業(yè)圖紙?jiān)O(shè)計(jì)方面的內(nèi)容體系、操作程序、培養(yǎng)學(xué)生綜合運(yùn)用所學(xué)理論知識解決實(shí)際問題的能力，為今后從事工程實(shí)際設(shè)計(jì)或施工工作打下基礎(chǔ)。
研究條件及應(yīng)用環(huán)境
原水條件：處理量Q=12000m3/d。夏季高濁時(shí)濁度為100－150NTU，冬季最低濁度30NTU。
出水水質(zhì)：出廠水濁度<1NTU。
圖紙條件： 廠地平整，以室外地坪標(biāo)高（±0.00，）為基礎(chǔ)標(biāo)高。出水通往市政管網(wǎng)，洪水水位以-10.00m計(jì)。
氣候與地質(zhì)條件：該給水廠位于我國北方地區(qū)，冬季最低氣溫為-35℃,夏季最高氣溫34℃,常年主導(dǎo)風(fēng)向?yàn)槲鞅憋L(fēng)，地震裂度為5級。
工作目的：
通過本次畢業(yè)設(shè)計(jì)可以培養(yǎng)學(xué)生一下幾方面的能力：
（1）加深對所學(xué)的基礎(chǔ)理論、基本技術(shù)能力和專業(yè)知識的理解，培養(yǎng)學(xué)生的綜合運(yùn)用所學(xué)知識的能力；（2）培養(yǎng)學(xué)生獨(dú)立工作、獨(dú)立思考和分析解決實(shí)際問題的能力，特別是培養(yǎng)學(xué)生的創(chuàng)新能力和實(shí)踐能力；（3）培養(yǎng)學(xué)生的圖紙?jiān)O(shè)計(jì)、文件編輯、文字表達(dá)、文獻(xiàn)查閱、計(jì)算機(jī)應(yīng)用、工具使用等基本工作的實(shí)踐能力。
二、參考文獻(xiàn)
[1] 中國市政工程西南設(shè)計(jì)院主編.給水排水設(shè)計(jì)手冊第1冊（常用數(shù)據(jù)）.北京：中國建筑工業(yè)出版社，1986
[2] 上海市政工程設(shè)計(jì)院主編.給水排水設(shè)計(jì)手冊第3冊（城市給水）.北京：中國建筑工業(yè)出版社，1986
[3] 上海市政工程設(shè)計(jì)研究院主編.給水排水設(shè)計(jì)手冊第3冊（城鎮(zhèn)給水）.第2版.北京：中國建筑工業(yè)出版社，2004
[4] 中國市政工程西北設(shè)計(jì)研究院主編.給水排水設(shè)計(jì)手冊底11冊（常用設(shè)備）.第2版.北京：中國建筑工業(yè)出版社，2002
[5] 嚴(yán)煦世，范瑾初主編.給水工程.第4版.北京：中國建筑工業(yè)出版社，1999
[6] 張智，張勤等編著. 給水排水工程專業(yè)畢業(yè)設(shè)計(jì)指南.北京：中國水利水電出版，1999
[7] 張智，張勤等編著. 給水排水工程專業(yè)畢業(yè)設(shè)計(jì)指南.北京：中國水利水電出版，1999
[8] 王海山主編.給水排水常用數(shù)據(jù)手冊.第二版.北京：中國建筑工業(yè)出版社，2000
[9] 姜乃昌主編.水泵及水泵站.第四版.北京：中國建筑工業(yè)出版社，1998
[10] 韓洪軍，杜茂安主編.水處理工程設(shè)計(jì)計(jì)算.北京：中國建筑工業(yè)出版社，2006
表2 畢業(yè)設(shè)計(jì)繪制圖紙要求
圖紙內(nèi)容
數(shù)量及尺寸要求
1
給水處理廠工藝總平面圖
≥1張，2號
2
給水處理系統(tǒng)的工藝流程及高程計(jì)算
≥2張，2號
3
給水泵站工藝圖
≥1張，2號
4
沉淀池工藝圖
≥1張，2號
5
絮凝池工藝圖
≥1張，2號
指導(dǎo)教師（簽字）： 王淑靜
20xx年 02 月 24 日
審題小組組長（簽字）：
年 月 日
1
外文資料
Development and application of some renovated technologies for municipal wastewater treatment in China
QIAN Yi,WEN Xianghua, HUANG Xia Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China
Abstract
China has been experiencing fast economic development in recent decades at the cost of serious environmental deterioration. Wastewater discharge, especially municipal wastewater discharge, and non-point pollution sources are becoming the major water pollution source and research focus. Great efforts have been made on water pollution control and a number of renovated technologies and processes for municipal wastewater treatment and reclamation as well as non-point pollution control have been developed and applied in China. This paper discusses the development and application of the appropriate technologies, including natural treatment systems, anaerobic biological treatment, biofilm reactors and wastewater reclamation technologies, for water pollution control in the country.
1 Introduction
With the rapid development of the industry and urbanization as well as the population growth , China is facing an increasingly serious water crisis in terms of water shortage and pollution. The annual average precipitation in the country is 648 mm and the water resource available per capita is 2220m3/a, which is only 1/4 of that of the world. The low treatment rate of municipal wastewater, illegal discharge of industrial wastewater, and non-point pollution sources have resulted in severe water pollution, expressed by the deterioration of surface water, the eutrophication of lakes, the increase of nitrate in groundwater, etc. Persistence organic pollutants (POPs) have been monitored in some water bodies.
To control water pollution in the country, thousands of scientists and engineers in this field have made great efforts in developing appropriate technologies of water and wastewater treatment. Preliminary progress has been obtained.
This paper reviews the development and application of the appropriate technologies, including natural treatment systems, anaerobic biological treatment and wastewater reclamation technologies, for water pollution control in China.
2 Appropriate process and technology for wastewater treatment in China
China is a big developing country with many environmental problems. Developing and applying appropriate wastewater treatment processes and technologies characterized by high efficiency and low cost, is an urgent need for water pollution control in the country. The characteristics of appropriate process or technology for wastewater treatment in China are as follows:
High system efficiency and stability in producing high quality effluent to be reused;
Lower energy consumption and operational cost;
Easy operation and maintenance;
Accommodating to local conditions;
Lower specific footprint to reduce the occupied land area and the investment cost.
In the following paragraphs, some examples of appropriate processes and technologies for municipal wastewater treatment and non-point water pollution control developed and renovated by Chinese scientists and engineers are discussed.
3 Natural wastewater purification systems
In ancient China, people used excrement and urine to manure the fields, which can be considered as crude natural wastewater disposal schemes. Nowadays, there is an expanding worldwide interest in the application of natural purification systems as a low-cost, effective wastewater treatment process to purify wastewater and recycle valuable organics and nutrients.
The natural purification processes, including land treatment systems and stabilization ponds, had been intensively studied during the 1980s to the 1990s [1–3] in China. The major research focus was the design, performance, cost analysis and mechanisms of pollutant removal in natural treatment systems. More attention to the natural treatment system has been obtained since the late 1990s in the country when non-point source pollution control was introduced. The major processes studied and applied include: rapid infiltration [4–6], slow rate filtration [7–8], overland flow [1,9], subsurface infiltration [10,11], constructed wetland [12–32], anaerobic, facultative, aerobic (aerated), high rate pond, etc. [33–43]. Various unit processes may be arranged in sequence to create an integrated treatment system [44–51].
Since 1990, large scale natural systems have been applied in many areas in China to treat municipal wastewater [8,13,23,28,36,42,47,48] and industrial wastewater [20,30,30]. Some demonstration treatment systems [7,10,14,16,18,29,52] were also established. Table 1 summarizes the effluent quality of different natural treatment systems.
The data in Table 1 show that all the applied natural treatment processes produced high quality effluent with low COD, BOD5, SS, TN, and TP. Moreover, the systems were very effective in removing potential and harmful recalcitrant organic compounds [20,40], heavy metals [30], chemicals and biological agents, including viruses [24]. Some kinds of selected plants, like mangrove and reed, were used for enhancing the treatment efficiency of municipal wastewater and for the plant-mediated remediation of persistent organic pollutants and heavy metals [15,27,31,53–55].
Although natural purification systems have high removal efficiency for various pollutants in wastewater, their performances are highly dependent on climate and temperature. They generally function well in warm seasons or in warm areas in south China. Operation at low temperature in winter or in cold regions in north China can be improved significantly by employing intensified measures such as adding biofilm carriers in ponds [42], artificial filtration layer [7], plant cover [16] and using integrated treatment systems.
Figure 1 shows a land treatment system applied in Shengyang City, located in the Northeast of China. Considering the low temperature in winter and the seasons for crop irrigation, a system combining a slow rate filtration process and a rapid infiltration process was designed. The slow rate filtration process runs from May 10 to November 25 and the rapid infiltration works in the rest of the year. The treated water is used to irrigate crops when needed or to inject into ground water.
Figure 2 shows a full-scale integrated treatment system including a stabilization pond and two stages of subsurface flow constructed wetland treating the mixed industrial and domestic wastewater in Shatian, Shenzhen City, Guangdong Province. The designed treatment capacity is 5000m3/d and the actual influent flow is in the range of 2000 to 10000m3/d. Under normal operational conditions, the final effluent quality meets the National Integrated Wastewater Discharge Standard (GB 8978–1996) very well. Seven species of plants were selected and grow in the wetland. It is noticed that the plants growing in the wetland are vulnerable to lower temperature in winter [23].
In the past few years, the Chinese government has paid great attention to lake eutrophication caused by non-point and point source pollution. Many investigators have been engaged in researching and developing natural systems for rural sewage treatment. There is a considerable body of literature on nitrogen and phosphorus removal efficiencies and mechanisms by natural purification systems [11, 21, 22, 56–64].
Figures 3 and 4 show two sets of natural systems in Dian Lake area, Yunnan Province, which have been successfully used for rural sewage treatment and achieved high nitrogen and phosphorus removal [65,66]. One is a subsurface infiltration system (Fig. 3). The other is a combination treatment system of two kinds of constructed wetlands with a biological pond (Fig. 4). Table 2 shows the performance data of these two full scale systems.
Nowadays, several investigators have began to pay attention to the long-term effects of various types of natural treatment systems on soils and ground water, and the possibility of bioaccumulation and migration of toxic materials to the human food chain. Proper system management, including adequate tracking monitoring, is necessary to assure ecological safety and human health [67].
Practical experiences show that the capital and operational cost of natural treatment systems is very low. Cost-effect analysis on land treatment systems and the comparison with an activated sludge system were made. The results show that the cost-effectiveness of the land treatment system is mainly dependent on the cost of land because the system occupies a large area of land. Results of cost-effect analysis show that there is a critical unit land price for the application of a land treatment system with different capacity. The critical unit land price is defined as the unit land price at which the total capital cost for the land treatment system equals to that of an activated sludge system. It implies that the application of land system is cost-effective or not depending on if the unit land price is lower or higher than the critical unit land price.
Figure 5 shows the critical unit land price for different natural application systems with different capacities based on the price of land in China in 1990.
The operational experiences also showed that land treatment systems required very simple maintenance. When a slow filtration system is used, the economic benefit can be obtained from the crop planted on the land.
Because natural treatment systems have such merits as high quality of effluent, low cost and easy operation and maintenance, they provide environmental, ecological and social benefits for the treatment of sewage in small cities, towns, and villages.
4 Anaerobic biological treatment processes
Compared with aerobic biological treatment, anaerobic biological treatment has significant advantages such as low cost, low sludge yield and energy recovery by utilizing generated biogas. It can also improve the biodegradability of refractory organics in the wastewater by acidification and hydrolysis.
The development of the high-rate anaerobic reactor has made it possible to treat municipal wastewater since 1970, which has been proven feasible by national and international experiences. Because the treatment efficiency strongly depends on temperature, most full-scale anaerobic treatment plants for municipal wastewater treatment are in the tropical areas.
Since the late 1990s, the price of crude oil has increased dramatically and a serious energy crisis appeared again. The application and investigation on anaerobic treatment of municipal wastewater have become a hot point in China again. The practices focus on:
1) Investigation on operation of high-rate anaerobic reactors treating municipal wastewater
The high-rate anaerobic reactors include:
Upflow anaerobic sludge blanket (UASB) reactor;
Anaerobic filter (AF);
Anaerobic baffled reactor (ABR);
Internal circulation anaerobic (ICA) reactor;
Expanded granular sludge blanket (EGSB) reactor etc.
Generally, a UASB reactor with 4–10 h hydraulic retention time (HRT) can remove 44%–82% COD and 73%–87% SS from municipal wastewater. AF has similar removal rates. ABR is a reactor with 3–6 UASB reactors without threephase- separators in series. It has a simpler structure and more stable performance. To solve the problem of low SS removal of ICA reactors, researchers from Tsinghua University introduced a new ICA reactor by replacing the settling part of the reactor with a filter layer. This improvement was proven with the better SS and colloidal COD removal. An ICA reactor with HRT of 4 h and organic loading rate of 2–4.7 kg COD/ (m3 · d) was used to remove 73%–87% COD and >90% SS. Table 3 lists some applications of high-rate anaerobic reactors for municipal wastewater treatment in China. Even for the high-rate reactors, aerobic post treatments are generally needed to meet the effluent discharge standard. However,the application could significantly decrease the investment and operation cost of a municipal wastewater treatment plant.
2) Improved processes with hydrolysis/anaerobic reactor as core treatment unit
The process consists of a hydrolysis or anaerobic step and an aerobic step has been developed in China for municipal wastewater treatment, which has the following alternatives:
Hydrolysis+aerobic process;
Anaerobic+aerobic process;
Multi-stage anaerobic+aerobic process.
In full-scale application, the most widely used process is “hydrolysis+aerobic process”. Ma et al. [68] used a hybrid hydrolysis+aerobic biofilter process to treat municipal wastewater of about 30 000 m3/d in Shandong Province and the investment was only 50% of that of the activated sludge process. The effluent COD, BOD5 and SS were <60, <30 and <20 mg/L, respectively. Because hydrolysis is less affected by temperature, the process is promising in China.
However,‘hydrolysis+aerobic process’ cannot generate biogas and the energy consumption in the aerobic unit is still high because hydrolysis can only remove 30%–40% COD. The ‘Anaerobic+aerobic process’ and ‘multi-stage anaerobic+aerobic process’ can compensate for the disadvantages of the ‘hydrolysis+aerobic process’ and evoke strong interests on a large scale. Table 4 summarizes the properties of the treatment processes with the anaerobic unit as the core technique.
3) Integrative installations for treatment of sewage from a building or community.
The practice of anaerobic treatment on domestic wastewater in China not only focuses on process but also on integrative installations. Integrative installations for the treatment of sewage from a building or community are rather popular in the country because it is a practical solution for water pollution control without huge construction fees and complex maintenance. Table 5 lists some data from integrative installations for the treatment of sewage from a building or community.
The general features of the integrative installations are low cost and simple maintenance by application of multi anaerobic stages and extended HRT (to several days) in some installations. The COD, BOD5, and SS removals could reach 70%–90%, 70%–90%, and 50%–98%, respectively.
The installations can not only be distributed in buildings and communities in cities but also scattered in corners of rural areas. Biogas is used to replace traditional fuel and the effluent and sludge of the installations are utilized as fertilizers for plants or feed for aquatic animals. In late 2004, 1.54 million families have had their own treatment installations and it is estimated that 0.12 billion families in China will have it in 2020.
5 Bio-film reactor
As the earliest bio-film reactor, tricking filter has been used in wastewater treatment for a long time. Because of its high operation requirement and low organic loading, some renovated bio-filters have been developed and applied for municipal wastewater treatment in recent years, as shown in Table 6. They are also applied in the post-treatment of secondary effluent [78].
A submerged bio-film reactor called bio-contact oxidation tank has been studied and applied for industrial wastewater treatment since the 1970s and is now applied to municipal wastewater treatment in China. It is very similar to the aerated bio-filter developed in Europe except the type and size of the media. Both plastic packing media and slag have been used in bio-contact oxidation tanks. Aeration is provided under the packing media and the flow pattern can be either up flow or down flow.
However, until 2002, the bio-contact oxidation process was not widely used. It was only used in nine wastewater treatment plants in China [85]. The reason is mainly related to the packing media. It plays an important role in promoting the bio-contact reactor performance. Many different types of packing media have been developed sequentially in the country [86], from the rigid packing media firstly used to the flexible, semi-flexible, combined, suspended, to the recently created enzyme catalyzed packing media. The major targets are to provide a larger surface area, larger porosity and better affinity to bio-film. With the development of packing media, it is expected that the submerged bio-film reactor will have even better performance.
The three-phase bio-fluidized bed (TPB) is another advanced bio-film reactor that has many advantages. The reactor was developed in the Netherlands where it is called the air-lift loop reactor. Intensive study has been carried out on TPB in China and it is now applied to both industrial wastewater and municipal wastewater treatment. The reactor is comprised of four zones: riser, downcomer, gas disengagement and solid sedimentation, while the riser and downcomer zones are jointly called as the reaction zone. Due to gas injection into a section of the reactor, the hydrostatic pressure difference is produced to cause the fluid to flow with the bio-carrier circularly. Because the biomass attached on the carrier lives in a suspended state, the technology has the combined advantages of a bio-film reactor and activated sludge process. Two types of three-phase bio-fluidized bed have been distinguished in recent years. One is the innercirculation three-phase bio-fluidized bed (ITFB) and the other is the external-circulation three-phase bio-fluidized bed (ETFB). Few researches have focused on ETFB [87] because less variety and modifications around the gas disengagement zone can be acquired, which is adverse to the reactor optimization. A kind of double cylinder ITFB(DCITFB) achieves more acceptance in China.
In DCITFB, the surface area of the carrier media is in the range of 2000–3 000 m2/m3, which is about ten times of that in the bio-contact oxidation process. A high biomass concentration can be up to 20–30 g/L in the reactor depending on the influent quality, carrier concentration and operation parameters. Such high biomass concentration contributes to a high loading rate varying from 5–20 kg BOD5/(m3 · d) [88]. Table 7 is the comparison between the performances of the conventional activated sludge process and the DCITFB process in municipal wastewater treatment [89]. It can be seen that the DCITFB process shows much better performance than the activated sludge process. The COD concentration in DCITFB effluent is below 30 mg/L although the aeration time is only 1/4–1/8 of that of the activated sludge process. The oxygen transfer coefficient is about 2–20 times of that in the activated sludge process. Apart from the organic pollutant removal, NH4 +-N removal loading rate can be up to 1.8 kg/(m3 · d) [90]. These advantages prove that the DCITFB is a cost-effective wastewater treatment process. Figure 6 is a picture of the DEITFB treating wastewater mainly from domestic users in a small-town (Zhoutiezhen) wastewater treatment plant in Yixing, Jiangsu Province. The treatment capacity of one unit reaches 2 500 m3/d. The quality of the treated water meets the national discharge standard.
There are many other types of ITFB developed in China as an improvement over the DCITFB. The high efficient separation composite biological fluidized reactor (HSBCR) is one of them [91]. In the reaction zone, the traditional double cylinder is replaced by the honeycomb-type cross section, which enables not only the aerobic zone and anoxic zone to concurrently exist but also a decreased height and diameter ratio of the reactor and hence energy consumption decreases accordingly. The high-efficient dissolved air floatation is coupled in the gas disengagement zone of the reactor, which improves the removal efficiency of SS. In addition, a mazetype carrier separator is added in the reactor to avoid losing carrier particles with the effluent.
Two types of pilot scale ITFB are used to treat municipal wastewater for comparison. One is DCITFB and the other is HSBCR. The performance of the reactors is summarized in Table 8 [92]. The re