Water Quality Remediation in a Heavily Polluted Tidal River in Guangzhou
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Water quality remediation in a heavily polluted tidal river in Guangzhou, South China Yanqing Sheng,1,∗ Fanzhong Chen,2,∗ Guoying Sheng,2 and Jiamo Fu2 1Key Laboratory of Coastal Zone Environment Processes, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China 2State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China ∗Corresponding author: [email protected]; [email protected] A field-scale experiment was performed to remediate a heavily polluted river located in the urban area of Guangzhou, China using biological and chemical techniques combined with engineering processes. Before comprehensive remediation was undertaken, several small-scale experiments to test river-water remedi- ation techniques were successfully performed. After comprehensive remediation, the average reduction rates of chemical oxygen demand and biochemical oxygen demand and removal rates of other pollutants were all above 70 percent. Furthermore, the unpleasant odor emanating from the polluted river was also greatly reduced. The field-scale experiment thus indicated the feasibility and validity of the method applied to remediate this heavily polluted river; this method can therefore be applied to remediate other heavily polluted rivers in the Guangzhou urban area and elsewhere. Keywords: comprehensive remediation, bioremediation, aeration, water body Introduction and nearly 80 percent of them are directly connected to the Pearl River. Therefore, the pollution of these With the continuing development of industry, rivers directly threatens the water quality of the Pearl commerce and other fields, Guangzhou is becom- River in the Guangzhou section (Tao et al., 1999). ing the political, economic, educational, cultural, Unfortunately, the water in some local rivers cur- scientific and technological center of the entire Pearl rently resembles black ink and emits an unpleasant River Delta. However, with the rapid population odor (these watercourses are locally referred to as growth and development of urbanization and indus- black-odor rivers), and such heavily polluted rivers trialization, increasing amounts of domestic sewage can be seen almost everywhere in Guangzhou city, and wastewater are being discharged into the munic- especially in arid seasons. Therefore, the study of re- ipal rivers. Although the local government has taken mediation methods for these rivers is necessary and some steps to resolve this problem, the results have extremely urgent. In recent years, local governments not been significant. Therefore, the quality of river have implemented a number of efforts to remediate water in Guangzhou urban area has been steadily the rivers, such as washing the riverbeds with tide- deteriorating. There are 231 rivers running through water, truncating the pollutant drainage and carrying the Guangzhou area and most of them have been it to the wastewater treatment plant by pipeline, and used as drainage ditches in recent decades. The to- covering the riverbed with concrete slabs. Washing tal length of these rivers is about 913 kilometers, the riverbed with tidewater consists of opening the 219 Aquatic Ecosystem Health & Management, 15(2):219–226, 2012. Copyright C 2012 AEHMS. ISSN: 1463-4988 print / 1539-4077 online DOI: 10.1080/14634988.2012.687674 Downloaded from http://read.dukeupress.edu/aehm/article-pdf/15/2/219/895867/219sheng.pdf by guest on 29 September 2021 220 Sheng et al. / Aquatic Ecosystem Health and Management 15 (2012) 219–226 floodgate at the entrance of the Pearl River when a ate a heavily polluted river in Guangzhou urban. flood tide occurs and closing it during ebb tide. After The objective was to explore and establish some ac- the ebb tide, the floodgate is fully opened to allow tual methods or techniques for heavily polluted river the water to flow into the Pearl River at a high speed, water remediation in site. The results of this study carrying with it a great quantity of pollutants. This demonstrated that the technique employed was fea- method obviously carries with it a higher risk to the sible and inexpensive, and a long-lasting remedia- water quality of the Pearl River. Some departments tion was achieved. have also used tap water to wash riverbeds, but this is too expensive to utilize in all the rivers. Although truncation of the pollutant drainage entrance and Materials and Methods diversion to the treatment plant does achieve some short-term benefits, it also faces many serious prob- Description of treated river lems. First, there are many rivers connected to each other and each of them has a large influx of polluted The experimental river is located in the Fangcun headwater, and long-distance transportation of the District of Guangzhou. The detailed location is indi- polluted water for treatment is very difficult. More- cated in Figure 1. The total length and average width ∼ ∼ over, the task of separating the polluted water from of this river are 1,000 m and 17 m, respectively. rainwater is also quite complicated. Second, some of This river was a typical scenic river in recent these rivers have had a history of pollution problems decades but has now become a black and odorous for over 100 years; there are black and malodorous river, and it greatly diminishes the scenic effect of sediments on the bottoms of some riverbeds ex- the beautiful buildings alongside it. The headwa- ceeding depths of one meter (Sheng et al., 2011). ters of this river consist mainly of domestic sewage To ultimately remediate the water environment, the and a small quantity of industrial wastewater. Of question of how to avoid recontamination should course, irrigation water and rainwater also feed into first be addressed. Third, after diverting the polluted this river periodically. The total influent volume headwaters, parts of these rivers run dry, exposing of domestic sewage and industrial wastewater fed 3 the black and odorous riverbeds on sunny days or from the upriver drainage is about 1,000 m per in arid seasons, with the diffusion of malodorous day. The depth of the river is about 0.1–1.2 m, and volatiles over the surrounding area (Muzeeinoglu, the thickness of the sedimentary sludge is about 2003; Sheng et al., 2008). Furthermore, this phe- 0.2–0.7 m (a length about 400 m of the bottom nomenon would obviously affect the scenic envi- of this riverbed was covered with stones in 1997). ronment of the Guangzhou urban area. Covering The height of the riverbank is about 3.6 m; it was a riverbed with concrete slabs also has its disad- built with concrete and large stones in the last few vantages, making it difficult to dredge with water decades. current when a blockage occurs and affecting the flood discharge on rainy days. Microbial culture and small-scale tests There have been only a few reports in recent Microbial culture years concerning the remediation of heavily pol- Two kinds of microbial reagents were utilized in luted rivers (Sun et al., 2009), and most of these this work. The dominant microbes in these reagents studies were focused on the analysis of polychlori- were photosynthetic bacteria (PSB) and Bacillus nated biphenyls (PCBs), organochlorine pesticides, subtilis. PSB are microorganisms that use sunshine persistent organic pollutants (POPs), polycyclic aro- as energy source and use naturally occurring or- matic hydrocarbon (PAHs) and other toxic com- ganic compounds and sulfur compounds for nutri- pounds dissolved in the river water or adsorbed tion (Chen et al., 2000). In addition to these char- in sediments (Fu et al., 2003; Zhang et al., 2004). acteristics, they also can perform photosynthesis Techniques using combined biotechnological and alone to remove the pollutants dissolved in a pol- engineering steps to remediate heavily polluted luted water body. In this study, samples containing rivers have been attracting increasing attention in PSB were collected from the sedimentary sludge the environmental-protection field. This study ad- of the Fangcun River (the treated river). After a dressed the applicability of using comprehensive series of enrichment, culture, separation and pu- bioremediation and engineering steps to remedi- rification steps, this PSB culture was identified as Downloaded from http://read.dukeupress.edu/aehm/article-pdf/15/2/219/895867/219sheng.pdf by guest on 29 September 2021 Sheng et al. / Aquatic Ecosystem Health and Management 15 (2012) 219–226 221 Figure 1. The location of the treated river (Fangcun River). belonging to the Rhodopseudomonas group. Cul- Artificial aeration ture medium mainly composed of CH3COONa, Dissolved oxygen (DO) is an important water- NH4Cl, NaCl, MgSO4,KH2PO4,K2HPO4,CaCl2 quality parameter. At a DO concentration below and yeast extract, ferment conditions were of tem- 2mgl−1, the creatures living in a water body will perature 30◦C, pH 7.5- 8.5, inoculation 20% and be endangered, even including several microorgan- 40-watt-bulb illumination. After six days, the bac- isms. Furthermore, sufficient DO in water body can terial abundance of PSB reached to 3–5 billion cells allow for the direct oxidation and rapid degradation per milliliter. This original reagent can be used di- of pollutants. Thus, increasing the DO concentration rectly through proper dilution. Another microbial in water body is one of the most important steps reagent applied in this experiment contained a great in remediating polluted water. However, the DO deal of Bacillus subtilis, and was also selected from concentration in the tested river water was almost the Fangcun River, carried on the complex clay. Its zero. Therefore, artificial aeration was applied in main function was to remediate the heavily polluted the small-scale experiments, as follows. Three clean sedimentary sludge and degrade dissolved pollu- glass boxes were prepared in an open field near the tants (Aiying et al., 2005). Several other chemicals lab, all of the same dimensions: 0.5 × 0.5 × 0.3 m used in this test were purchased from local markets (length, width and height, respectively).