Shuzo Nishihara, Nishihara Environmental Sanitation Research Corp., Ltd., Tokyo, Japan
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River Can Be Made to Help Itself
River’s natural capacity for self-purification helps minimize the costs of pollution control and provides unexpected opportunity for unusual recreational benefits
The most important task in cleaning up the Sumida River is to find a satisfactory way to treat a large quantity of waste. Basically, we consider it necessary to reduce substantially the concentration of pollutants in the sediments in the river, sea, and seashore, where they have been accumulating for several decades, and require factories to install reasonable primary treatment plants according to the permissible limit of their wastes. When these measures are put into practice and the settleable solids are removed from wastes, water could be kept clean by the river’s natural capacity for self-purification. Keeping these goals in mind, we designed a system of portable treatment tanks under central control. Preliminary pilot plant
Experimental plant
710 Environmental Science and Technology
The Tagara River is a small stream that flows through Itabashi Ward, Tokyo, where there is no central sewage system. The stream is considerably polluted by a large quantity of domestic sewage and a relatively small quantity of industrial wastes. The experiment at the Tagara River was a pilot plant operation preliminary to the clarification of the Sumida River. Since the Sumida River has a large volume of flow, we decided to utilize the river’s natural capacity for selfpurification so as to minimize operational costs, particularly the cost of electric power, and simplify construction and operation. Thus, we set the treatment rate at 40 to 65 % , and assembled all the unit processes in one tank.
Treatment tanks
The tank is circular, with pumps and pipe gallery in the core, mixing chamber and sludge aeration chamber in the middle, and a sedimentation chamber on its circumference. In each tank, three different types of vertical axis pumps are installed in the center gallery, and two regular air compressors and one spare are installed in the pump room, which is located between two such tanks. An automatic control apparatus for each tank is also installed in the pump room, and two tanks are controlled as a unit. Each automatic control apparatus is operated from the group control center. The intake is a wooden frame filled with gravel. At the center of the frame, perforated reinforced concrete piping is installed. Because of the intake, such facilities as grit chamber, screen, and primary settling tank can be eliminated. In the sludge aeration chamber, 168 mechanical air diffusers are installed, and in the mixing chamber 168 jet diffusers (stream water and compressed air diffuser) are installed. Sludge aeration chamber detention time is 120 minutes; mixing chamber detention time, 23 minutes: and sedimentation chamber detention time, 100 minutes. Installation
These treatment tanks would require a large surface area if they were constructed on land. F o r this reason, we
FEATURE
decided to install the treatment plants on and over the surface of the river, and to utilize the top slabs of the tanks. made of precast concrete plates, for various facilities such as parks, heliports, playgrounds, parking areas, restaurants, athletic grounds. and the like (see ES&T. February, page 173, for a Japanese hotel and amusement complex built atop a sewage plant). Three methods for installing the treatment plants on the river were contemplated: Installing the plants on the surface of the water. Fixing in the water. Floating. There are certain advantages and shortcomings in each method. Therefore, taking into consideration such factors as variation of water level of the river, depths of the river, shape and function of the treatment plant, the combination of the three methods has been adopted. Part of the weight is supported by piers, part by submerging a portion of the tank in the river. and part by floats. This method is considered to be the most reasonable way to satisfy all the conditions.
Flow diagram of the experimental plant
Mixing chamber
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Sedimentation chamber
-0.0 Excess sludge Return sludge Sludge aeration chamber
Subunits
The main structure of the tank consists of a compression arch frame and bottom membrane. Each tank-a plant unit-is manufactured in 16 subunits. A subunit consists of an arch frame, a bottom membrane, an exterior shell, an interior shell. a float, and a net-cylinder for mounting the float.
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Cross sections of the high-rate activated sedimentation tank
Pumps
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Float
Each subunit manufactured at the factory is sent to the dock, where all are assembled in one large unit and equipped with a protection net. When the assembling is completed, the unit is floated and towed to the setting point in the river and fixed on the 16 pre-installed piers. When preliminary treatment plants for wastes are installed in factories, and when the river becomes clarified, the tanks can be released from the piers and floated and towed to other polluted rivers. Sumida River
The Sumida River is a branch river of the Arakawa River, and its flow is controlled by the sluice gates at Iwabuchi. There are two more sluice gates,
712 Environmental Science and Technology
Float
one at Horikiri (11 kilometers downstream from Iwabuchi) and one at Azuma (which is 3.5 kilometers farther down the river). The flow of two flood control canals, the Arakawa Canal and the Nakagawa Canal, as well as the flow of the Sumida River, is controlled by interchanging water by these three sluice gates. The gates protect Tokyo metropolitan district from flooding. Tokyo metropolitan government has a 5-year plan to dredge the Sumida River. From the mouth of the river to the Joban Railroad (9 kilometers upstream) is scheduled to be dredged to a depth of at least 3.0 meters, and from there to the Iwabuchi sluice gate is to be dredged to a depth of at least 1.8 meters, with a grade of 0.0001 for
the distance of 12 kilometers from the starting point. The flow of the Sumida River is 85.0 cu.m./second, with 71.5 cu.m./ second back flow of sea water at high tide. The Shinkashi River flows in at the upper boundary of the river. Pollution sources
Of approximately 2000 factories along the Shinkashi River, 320 factories should be required to install complete pretreatment plants. Wastes from the Shinkashi River are responsible for 27.6% of the total pollution of the Sumida River. There are 6000 factories along the main stream of the Sumida River, of which 260 should be required to install pretreatment plants.
Experimental plant for high-rate activated sedimentation process Compressed air
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Rawwater
Effluent
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Return
er
Two other branch streams contaminate the Sumida River, too. One, from Koto District, is responsible for 37.7% of the pollution of the Sumida River (its wastes are 92.0% industrial); the other is the Kanda River, which contributes 26.4% of the pollution load (its wastes are 13.0% industrial and 87.0% domestic sewage). In the Koto and Senju Districts, the main source of pollution is small-scale plating factories-almost 10,000 in number. There are also small meat factories and dye factories which discharge highly polluted wastes. As these small factories have no legal obligation to install pretreatment plants, the government must provide necessary pretreatment plants at public expense. Dumping of refuse and night-soil into rivers is another source of pollution. Strict control of these activities is also necessary. Otherwise, the Sumida River will never be cleaned up. Survey of factories
A. Sludge aeration chambe E. Mixing chamber
C Sedimentation chamber
A survey of factories, including analysis of wastes and processes of production, was conducted preliminary to designing suitable pretreatment plants for each factory. Twenty-five factories were intensively investigated by Dr. F. Nakajima. Wastes were classified as food industry, paper industry, chemical industry, metal industry, cement industry, or dye industry. Wastes from 24 of these factories-all but one-are discharged into the Shinkashi River. Separate tabulations were prepared for wastes which are discharged continuously and those which are discharged intermittently. Continuous wastes are separated into cooling water, which does not need to be treated (and in fact can be used as dilution water), and wastes which require treat-
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Flow diagram of the high-rate activated sedimentation tank
Influent
Effluent
Excess sludge
ment, and the percentage to total volume of discharged water was calculated for each. Indexes of pollution, such as COD and acidity and their percentage to preceding factors, were also classified by industry. Volume of water required for a ton of product and typical analyses of mixed wastes were recorded, too. Armed with this information, we undertook the pilot plant operation outlined at the beginning of this article. Personal experiences
During my studies of the ever-increasing industrial waste problem, I have come across a number of instances of pollution, and I would like to recount some of my personal experiences. On December 15, 1961, at the seashore of Kanazawa Hakkei, Kanagawa Prefecture, laver (seaweed) was damaged by the plating waste discharged from a nearby factory. The waste destroyed the cellular tissue and brought about decolorization of the laver by disintegrating pigments, which resulted in 30 to 40 million yen worth of annual injury. At the same time, fry of the goby fish were killed and floated up on the surface of the water.
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A n investigation revealed that the damage was caused by the waste overflowed from a plating bath of an automobile factory. The waste was being discharged without sufficient treatment. Since this had been a favorite fishing resort of mine for almost 40 years, I presented the data on laver damage to the automobile factory through the director of the local fishermen’s union on February 4, 1962. But while the negotiations dragged on, the swimming season drew near. Since the place was a summer resort as well, on June 30, 1962, I again presented a request, this time in my own name, to the factory, through the director of the union. to provide separate piping for plating wastes, store the wastes in a holding tank, and give suitable treatment before discharging it to the sea. I requested the factory to treat strong acid wastes using the same method, too. This suggestion was implemented, and there was no harm during the swimming season. Laver recovered by December 30, 1962. However. there was some reduction in yield due to the unusually low water temperatures which occurred in January 1963. At present, there seems to be no damage by sodium cyanide. The case mentioned here is evidence
that relatively simple pretreatment can prevent damage when plating bath wastes are to be discharged into the sea. A small quantity of the sodium cyanide contained in the wastes can be diluted by sea water, or aerated by the turbulance of the waves, and it will become harmless. The place, Kanazawa Hakkei, is il well known and historical place, known particularly for the Kanazawa Kunko (an old library which dates from before 1312) and its beautiful scenery, laver cultivation, and the beautifully maintained beaches-one of the best swimming resorts in Tokyo Bay during summer time. It is very fortunate for public welfare that this lovely place is n o longer injured by dangerous industrial wastes. On February 22, 1962, after the incident of the first automobile factory, another incident occurred-caused by the waste discharged from another automobile factory in the suburbs of Fujisawa City. Waste was discharged to the small stream, where there is a n intake of dilution water for Fujisawa City Night-Soil Treatment Plant nearby downstream. The digestion tank of the night-soil treatment plant was badly affected by the waste, and its gas production dropped to one third of its ordinary level. At the same time. 250 roach ( a species of fish), which were grown in a pond of the treatment plant, were killed, because the pond used the water from the same river. In this case, we presented a letter of suggestion (the same as the previous one) to the automobile factory through Fujisawa City Office. Then the quality of the river water was restored to the original state. On October 12, 1962, the intake pump for dilution water stopped suddenly. We disassembled the pump and found two huge eels-about 80 cm. long and weighing about 1 kilogramand two days later we caught two more rather smaller eels. As the usual size of eels in the Hikichi River is about 20 cm. long, and the night-soil treatment plant had started its operation on February 22, 1961, and its function seemed to be well established around July 1961, it was evident that the eels had grown to that size within a period of 16 months. The reason that the waste did not damage the eels was that sodium cyanide contained in the waste was dispersed into air as a cyanic
Intake of river water
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crr"al
Perforated reinforced CanCrete pipe
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Jet diffuser River water or effluent
c.Campressed air
Shuzu Nishihara (deceased) was founder and president of Nishihara Environmental Sanitation Research Corp., Ltd., Tokyo, Japan. Mr. Nishihara was a graduate (1898) in civil engineering of Kohshu Gakko and completed (1904) an English language course at T o k y o School of Foreign Languages. Previously (1917-57), he was founder and president of Nishihara Engineering Works, renamed (1948) Nishihara Engineering Co., Ltd., to which he succeeded as chairman in (1957). From 1899-1915, he held various governmental positions in civil engineering. On several occasions Mi-. Nishihara was honored with presentations by the Japanese government f o r his contributions t o sanitation and the development of waste water disposal technology: in 1965 with the Fourth Order of Merit of the Sacred Treasure, in 1956 with the Public Health Award f r o m the Ministry o f Welfare, and in 1955 with the Yellow Ribbon Medal. H e was a member o f the Society of Heating, Air Conditioning, and Sanitary Engineering of Japan, Japan Environmental Sanitation Association, Japan Science. Foundation, and Architectural Institute of Japan.
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Air and water mixed
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Benefits. Concrete sewage tanks in river offer additional service and recreational areas
acid by the aerative action of the stream, and it did not adversely affect the fishes that live near the bottom of the river. Fish growth
I would like to explain here how the effluent from the night-soil highrate digestion process is effective for the growth of fish. The BOD of nightsoil is about 8600-10,000 p.p.m., and it becomes 2600-3000 p.p.m. as a supernatent after high-rate digestion. After being diluted by fresh water and effluent by 15 times, the supernatant receives secondary treatment with a highrate trickling filter, final settling tank, and chlorination. The BOD of the final effluent is about 30-80 p.p.m. When this effluent is supplied to a pond or a river, it makes the COD of water about 15-20 p.p.m., and has the effect of accelerating the growth of fish. Growth stimulating factors in supernatant are considered to be rich in vitamin BI2 (15-20 pg. in dry solids) and other microelements. 716 Eiivironmental Science and Technology
I should also like to explain about the condition of marine products in Tokyo Bay and how they are affected by water pollution. In 1938, when Tokyo Bay was in a favorable condition for laver cultivation, annual production of laver was 24,500,000 sheets (size 19.5 cm. X 18 cm., and its present price, 10 yen per single sheet), and its value averaged 245 million yen. Production has been reduced to 180,000 sheets annually in 1963. Fish in Tokyo Bay smell of phenol and are nothing like fish in the old days. Water pollution control is an urgent requirement in this area. Plating factories
As I mentioned before, there are many small plating factories and meat processing factories (usually for hogs or poultry), most of them on the scale of domestic industry. And it is very important to provide them with some means of treating their wastes. Otherwise, clarification of the Sumida River will never be realized.
My proposal is to request the metropolitan government to construct four kinds of holding tanks for small plating factories to store their wastes separately as chrome, copper, sulfuric acid, and nitric acid, and collect them separately, by vacuum tank trucks, periodically. When collecting chrome and copper wastes, the vacuum pump will operate in reverse so that it can be used as a compressor and will diffuse cyanic acid into air instantly by aerating the wastes; then wastes will be collected. Collected wastes are carried to treatment plants where chrome waste is treated by electrolysis, copper and zinc wastes by ion exchange, and these metals recovered from the wastes and returned to the original plating factories. Organic wastes are treated by any suitable high-rate digestion process or high-rate activated sludge process, and recovery of new resources is also considered. By these methods, I think we can really turn a misfortune into a blessing.
