Introduction:- Due to rapid changes in the developmentof economy and rise of urbanization, the urban river polltion occurredcontinuously,which causes changes in the river ecosystem and criticallydisturbed the ecosystem.A very large amount of domestic and industrialwastewater spilled into the river and polluted the water system badly. Due towhichriver function as a water resource was lost and urban ecology and aquaticenvironment were declined. The causes of urban urban river polltion andecological effects of urban river polltion are becoming more hypercritical. The objective of study was to determinepollution in river water, sediment and fish to evaluate polluted andnon-polluted locations. Water quality can be improved by artificial aeration.
Surface water act as a receptor ofpollutants which come from urbanized attachments or water heads Rapidurbanization leads to degradation of water quality with eutrophication andpollution.According to the statistics, by theearly 20th century, there is no complete natural river in the world.Therefore,it is necessary to develop a cost effective techniques to reduce water pollutionand its side effects and to increase water quality.Remediation Techniques:Physical Remediation: Aeration: Aeration can re-establish and increasethegrowth and capacity for survival of micro-organisms to improve the river waterquality. The aeration method is a simple and effective method which came inexistence to be utilized since to return the early river into its originalcondition. A technology having numerous applications and factors should be taken into account,includingriver conditions, source properties, water quality rising improvementsand etc. havingthe fixedaeration, mobile aeration and water aeration methodswhich are selected to deal with the pollution control to improve water quality over a short period oftime. Since the 1960s, the mobileoxygenation method was used as well as thefixed aeration method for the urban river aeration, which was simple method andused by many countries to reduce urban urban river polltion.
Presently, the use of river aerationmethod in foreign countriesshowed that the artificial aeration can improvewater quality efficiently. The river aeration method has been used successfullyin the treatment of the Oeiras Riverin Portugal, the Emsche River in Germany,Thamas River in UK and Homewood Canal in U.S. Theaeration equipment was used inthe treatment of the Homewood Canal of U.S. in 1989, whichenhanced thedissolved oxygen in bottom water and by which the biomass of river wasincreased. Theriver aeration method was utilized to enhance the river waterquality efficiently in Germany in 1994. The riveraeration method was applied toreduce the black-odor of water in Busan South Korea.
To improve the environment, eightaeration equipmentswere placed in Qing River with eachpower of 11.025 KW duringBeijing Asian Games as early as 1990, by which the level of dissolvedoxygenrose from 0 to 6mg/L, and the removal rate of BOD5 also reached 60% by which allodors in the riverare removed. Shanghai Academy of Environmental Sciences had setsome aeration pointsin the river channel to perform the practical of wateraeration and bioremediation. By this practical,the dissolved oxygen level ofthe water body (was in anaerobic condition originally increased), theproduction of the aerobic microorganisms was enhanced greatly and theremovalrate of organic pollutants in water was up to 10.7% -23%. The concentration of BOD5 andNH4+-Nlessened by 2.492mg/L, 1.217 mg/L and 0.
322 mg/L after aeration in theGuanchengsection of the Dongguan Canal. By using BIO method, Wang Chengxin and conducteda pilot study onaeration in Shanghai Suzhou River. The results expressed thatthe pure oxygenaeration could lessen the COD of the black-odor water and theremoval rate could reach from 19.5% to56%.WaterDiversion to Flush Out Pollutants:Through water diversion,it is feasibleto control urban river polltion. The clean water can dilute pollutedriversresulting in the black and stink of water body remove quickly and theself-purification capacityof water body improved. The water diversion to flushout pollutants was applied in Fuzhou, Zhongshan andother cities in China inwhich the calculation of diversion scale was the key technology based on theeffluentwater quality. For instance, Hong Lijian examined the effect offlushing out pollutants of diversion scaleabout Fuzhou River thay was appliedto engineering design but the project was large and the cost was relativelyhigh.
Sedimentremoval:The different dredging methods canproduce different environmental effects. Usually,resuspension of sediment will becaused by the extensive operation way of grab or drag-suction dredger. Thewaterinjection dredging was a type of sediment dredging method in situ by which efficiencyincreaseand reduce cost and this approach was adopted in the sediment dredging of UKport channel and XuanWu Lake in China .
Cutter suction dredger is the latest typeof environmental dredging and such dredging boat bounded with the automaticcontrol and monitoring systems to improvedredging accuracy greatly. It was usedin the Wu Li Lake, Chao Lake in Anhui and Dianchi Lake inKunming in China todredge sediment.ChemicalRemediation:Flocculationand Sedimentation:The sedimentation and flocculationmethod can be used to the water treatment by a large numberof suspended solidsand algae that was simple to operate and easy to maintain. It was effective to treat.The infrastructure costs and pharmacy costs were high. At the same time, it wasconnected withsecondary pollution hence it cooperated with other processes as apretreatment phenomenon. Poly aluminum chloride (PAC) flocculation wasnon-polluting, that wasfor recovery and removal of algae.
The concentrationofPAC was 5mg/L, the time of rapid mixing was 3min, the concentration of caseinwas 15mg/L, and pH=7-8 for the best agent suction.Removalof Algae by Chemical Agent:Copper sulphate was used for algalremoval (also bleaching powder, alum,poly aluminum and ferrous sulfate. Effectively,it could remove the algae and reduce the smell of water to put the coppersulfate which alter PH of water.
Thecalciumhypochlorite can kill the green algae, cyanobacteria and diatoms which causingthe water bloom. On the treatment of cyano-bacterial bloom based on chemicalalgicide with mainingredient of acetic acid, the research was carried out inXuanwu Lake in Nanjing in 2005 by which, after the treatment, the total algaeof theexperimental area reduced by 82.8%. Bioremediation Technologies:Indigenous or cultivated microbes andother organisms are used in bioremediation totransform the harmful and poisonouspollutants to non-toxic substances under the controllableenvironment. In order to eliminate the gasoline pipeline leak inPennsylvaniain 1972 bioremediation process was used. It played a significantrole as the main means. It was likely the firstlarge-scale application at thistime.
It was a important step in the development of bioremediation andattractedmore and more concerning.The bioremediation could be dividedinto artificial and natural bioremediation according to the degree of humanintervention, and the prioer could bedivided into in-situ bioremediation and ex-situbioremediation. The in-situbioremediation, on one hand, means to use bioremediation technologydirectly inpolluted rivers without any pollutant transported. Indigenousmicrobes whichsometimes combine with domesticated microbes are used by this method. In theEx-situ bio-remediation the polluted water was taken out from the contaminatedareas for transportation.Therefore, the bioremediation wasadvancedrapidly from 1990as engineering technology for urban river polltioncontrolling,. There are many benefits for the bioremediation technology, suchas reduced cost with low environmental influence, reducingpollutantconcentration by the maximum extent,no secondary pollution orpollutant movement, available for the sites where general pollution treatmenttechnologyis hard to be applied.
This bioremediation technology is the only mostpromisingremediation.Remediation by aquaticplants: Aquatic plants have a certain degree ofpurification for water. The plants having good absorption capacity for aquaticpollutants could be implanted in the dirty and polluted water. Similarly waterpollutants were fixed by adsorption, absorption, accumulation anddegradation bythe plants for water purification.Based on the laboratory experiments,GuoChangcheng and his group verified that thepotamogeton had good cleansingresult for the polluted river water. Tong Changhua used aquatic plants toremove eutrophication from the urban river water. The results revealed that aquaticplants had a good capacity to remove TN, TPand nitrate nitrogen. Foxtail alga andgrain leaf pondweed could efficiently remove TN (83.
84% and 77.54%), TP (91.3%)and nitrate nitrogen (95.85% and 90.65%), but had no substantialeffect oneliminating ammonia nitrogen (only 14% to 70%).Remediation method byaquatic animals:The aquatic animals were used to reducethe water of algal bloom and to modify theaquatic nutrition by changing theconfiguration and density of fish. The algal bloom formed by phytoplankton canbe removed by the use of silver carp, common carp and other filter-feedingfish.
MicrobialRemediation Method:Bio-filmformation:The bio-film method uses bio-membranewhich is fixed to the natural river bed and micro-carrier tomove thecontaminantsof the river by adsorption,degradation and filtration through theartificial aeration or dissolvedoxygen.The bio-film study showed that its structure can be affected by watercondition and by the structure of substrate.The bio-film formation method for purification of river in Japan, South Korea and other countries were gravelcontact oxidation method, artificial packing contact oxidation method, thinlayer flow method and underground stream purification method.
Japan used thegravel contact oxidation method for water purification of river and the removalrates for BOD and SS were significant. In china by using non-woven fabric aspacking substrate then removal efficiency of SS reached to 97 %, for BOD 88%.Park, Y. K.used biological activated carbon to sieve and clean the pollutedKumbo River water, and theremoval rate for ammonia was 90% and the removal rateof TOC was also significant.
Lei Jin Yong used the composite pcking of pebblesand zeolite for bio-film formation for the degradation of organic matter,ammonia and nitrogen. MicroorganismDosing method: This technology utilizes the specificand effective microorganisms for the absorption, purification and transformationof the contaminants in the river water. The production of highlyactive compoundbacteria was the significant step to determine the influence of microorganismdosing.At that time, it was studied and utilized for the purification of sewage,industrial wastewater and for the water of algal bloom. FLO-1200achieved remarkable results in the urban river polltioncontrol under theconditions of river aeration.
Conclusion:Theresearch in foreign countries started in Japan, U.S and some other Europeancountries for river control in the 50s of 20th century and afterthat urban river polltion control became an international problem. Chinastarted research work for river control in 1990s and has done much remediationwork.· To obtainecological development of the river ecosystem, the river should be treatedwithbio-eco remediation and with physico-chemical remediation.· Bioremediationmaterials should be checked and the mechanism of bio-remediation should bestudied carefully before it is directly applied to the river.· The generalconditions of many technologies such as aeration, bio-film and microbialformationand dosing for river pollution control are investigated.· The waterpollution control for Nansha River developed by using coupled model based onthe models EFDC and WASP.
For scenario analysis coupled models which lead torecommendations to improve water quality in Nansha river. Estimation of amountand distribution of waste-water from domestic and industrial waste water basedon the waste water treatment plant (WWTP) scheme developed by public authority.