生态技术在环境修复工程中的应用

生态技术在环境修复工程中的应用

北京正和恒基城市规划设计研究院（以下简称“正和恒基”）多年来参与了许多城市水环境管理项目，并获得了两项专业水处理技术。你有什么经验可以分享我们？。邢磊(以下简称邢):就我国目前的普遍情况来说,城市集水区往往受到较为严重的污染,并且大部分水域与城市水循环系统相脱离,导致城市水资源不平衡,城市水体调控能力弱。因此将水利、生态与景观领域相结合,提出设计方案,并将相关生态技术应用到环境修复建设中,达到改善水质、重建生境、还原一个健康自然的水生态系统的目标,并使其具备稳定性、可持续性,已成为目前设计行业的重要议题。但在目前国内城市水生态环境治理的项目中,还存在很多不成熟的现象,例如,在解决水生态环境问题上缺乏系统性,虽然某些单项的技术比较成熟,但是仅仅依靠这些单项技术难以应对城市水生态环境所面临的复杂问题。我们的设计团队通过与诸多相关领域专家的协作,依循“七水共治”(水安全、水环境、水资源、水经济、水生态、水景观、水文化)的水务一体化技术理论体系展开实践探索,即在安全保障的大前提下,协调统筹资源与环境以及对经济因素进行考量,并从生态、景观、文化三个维度,实现对水岸空间的营造。在山西孝义胜溪湖湿地、贵州威宁草海湿地、河北唐山曹妃湖湿地及石家庄环城水系人工湿地、内蒙古呼和浩特八拜湖湿地等近百个水环境治理项目的实践过程中,我们逐步积累了丰富的经验与生态技术库,拥有了如自净型表流湿地技术、沉沙前置库技术、组合式好氧生物流化床污水处理技术、木桩生态驳岸技术等30余项自有知识产权。这些技术都具有良好的生态效益。以“木桩生态驳岸技术”(图1)为例,这类驳岸的建造不仅可以就地取材,而且也有利于水陆交接带的栖息环境的创建。木桩驳岸形成的缝隙有助于腐殖质附着和植物根系生长,以吸引野生动物前来,从而成为水陆间生态流的交换通道。水陆交接带栖息环境的形成,能有效地提高水体的自净能力。此外,木桩驳岸不仅造价相对较低,施工方式也简单快捷,能有效提高施工进度及效率。而且,木桩驳岸为柔性驳岸,在我国北方的冬季环境中,能很好地解决驳岸冻胀问题。您能否结合正和恒基具体的项目实践,来谈谈如何在水环境治理项目中统筹考虑生态环境的改善与公众的活动需求?乔旭(以下简称乔):孝义胜溪湖湿地公园可以说是黄土高原上的一个奇迹。孝义市是全国著名的焦煤产区,焦煤生产给当地带来了巨大的经济效益,但也造成了严重的环境污染。胜溪湖湿地上游河流挟带来的大量煤灰、泥沙等颗粒物,造成湿地泥沙淤积、库容量急剧缩小、水质恶化、洪水安全隐患增加、生态环境严重退化等一系列问题(图2)。对此,在景观规划设计中,我们通过对生态修复与重建机制、雨洪系统管理机制、场地构建机制等进行整合,实现了生态系统的修复及人性化场所空间的营建。2014年初,这个有自然净化力量的“流动花园”展示在公众面前(图3)。有别于一般的城市公共绿地,这里有着与自然风貌更接近、季节性变化更丰富的景观,为公众提供了可以真正亲近自然的滨水体验。丰水期时,雨水收集池、跌瀑及生境岛形成连续的、流动的湿地景观。枯水期时,水泡散落在场地中(图4)。胜溪湖之所以能够将曾经饱受污染的场地变为人们喜爱的丰饶湿地是因为其拥有两个功能强大的内部系统:由沉沙池、泄洪渠、胜溪湖水库形成的水资源调控系统,以及由沉沙池、表流湿地等形成的水质净化系统。我们结合对不同洪水过程中泥沙淤积分布的分析(图5)设计了沉沙池,沉沙池的过水断面远大于上游河道的过水断面,水流通过沉沙池时流速减小,挟沙能力降低,使水流中的泥沙沉淀在特定区域,同时提升了湿地的水资源调蓄能力。在洪水来临时,湿地系统还可以通过泄洪渠来保障城市安全。经沉沙池初步沉淀后的水流以及周边村庄的降雨径流将在人工湿地得到进一步净化。人工湿地利用现有坑塘和空地设计出25个平均面积780m我们所面对的环境本身就是多维的、充满复杂性的,所以针对场地所进行的改善及恢复工作是一个涉及多专业的系统化过程。在孝义胜溪湖湿地项目中,设计团队多次与水利团队、泥沙专项研究团队、生态团队、水处理团队等专业人士进行沟通和协作,通过水动力沉沙模拟、湿地净化、栖息地恢复、雨水管理等方面的探索,达到了解决泥沙淤积和净化水质的目标。在该项目建成之后,湿地的实际运作效果如何?乔:项目建成后,我们对湿地的运行情况进行了持续监测。最近一次对湿地不同位置的水体进行检测的结果表明,胜溪湖湿地在改善水质方面效果显著(图7):污染物浓度逐级下降,水体透明度逐渐提高。其去除氨氮(NH在胜溪湖湿地公园的实施过程中,我们依据实践绩效的反馈,不断调整设计方案,稳步实现了生态系统的重建,这也基本达成了设计之初的构想。在公共政策的推动之下,全国多个城市已在陆续开展“海绵城市”的建设,您认为这将为景观设计师带来怎样的影响?邢:参与到海绵城市的建设中我们将面临诸多挑战,例如场地水文、土壤、气候等原始资料的缺失;参与其中的规划、设计、建设团队对于“海绵城市”技术的理解程度参差不齐;而且这些建设项目面临着三年之内就要初见成效的考验。但这些挑战也意味着机遇,景观设计师需要拓展生态学、水文学、气候学、城市给排水等专业的知识及技术,从而能更好地与其他专业人员进行协作,提出更加有效的解决方案。BeijingZEHOWaterfrontCityPlanningandDesignInstitutehasbeenpracticingurbanwaterecosystemimprovementforyears,andhasobtainedseveralpatenttechnologiesinwatertreatment.Couldyousharesomethoughtswithus?LeiXING(XINGhereafter):SpeakingofthesituationofChina,urbancatchmentareastendtobecomemorepolluted,andmostofthewaterbodiesaredetachedwithcity’swatercirculationsystem,resultinginanimbalanceofurbanwaterresources,andimpairedcapacityforselfadjustment.Therefore,tointegratedesignwithwatermanagement,ecologyandlandscapehasbecomeanimportantsubjectintoday’sdesignindustry.Ecologicaltechniquesareusedinenvironmentalremediationandrestoration,soastoimprovewaterquality,reconstructhabitats,restoreahealthyandnaturalwaterecosystems,andachieveasustainablylong-runlandscapeperformance.However,amongmostoftherecentwaterecosystemimprovementprojectsincitiesofChina,therearestillmanyimmatureaspects,suchasthelackofsystematicconsiderationonthewaterecologicalproblems.Althoughsomeproven,individualtechniquesareapplied,itisinadequatetodealwiththecomplexityoftheoverallurbanwaterenvironment.Ourdesignteamcollaboratedwithexpertsfromrelatedprofessionsbasedonaframeworkcalled,“DealingwithSevenAspectsofWaterAltogether”(secutity,quality,resource,economy,ecology,landscapeandcultureofawaterenvironment)thatestablishesatechnicalstrategyofintegratedwatermanagement.Inthepromiseofwatersecurity,thestrategyhelpsgenerateacomprehensiveplanforcoordinatingwaterresourcesandimprovingwaterqualitywitheconomicconsiderations,andcreatinganecologically,aesthetically,andculturallysoundwaterfront.Wehavewidelyappliedthetechnologiesinnearly100waterfrontprojects,includingXiaoyiShengxiLakewetlandinShanxi,WeiningCaohaiwetlandinGuizhou,TangshanCaofeiLakewetlandandtheconstructedwetlandsystemforthewatercirculationofShijiazhuanginHebeiandHohhotBabaiLakewetlandinInnerMongolia,andgainedrichexperiences.Wehaveestablishedanecologicaltechnologyinventory,withmorethan30intellectualpropertyrights,suchasself-purificationsurfaceflowwetlandtechnology,presedimentationforebaytechnology,combinedaerobicbiologicalfluidizedbedsewagetreatmenttechnology,andecologicalstake-revetmenttechnology,etc.Thesetechnologiesallcanbringgoodecologicalbenefits.Taketheecologicalstake-revetmenttechnology(Fig.1)asanexample:first,materialsforbuildingsuchtypeofrevetmentcanbefoundlocally.Second,itisbeneficialforthecreationofhabitatsinriparianareas.Thegapsformedbystakesaregoodforhumusattachment,aswellasplantrootgrowth;italsoattractsriparianwildanimals;itbecomesanexchangechannelfortheecologicalflowsbetweenwaterandlandthateffectivelyhelpsimprovetheself-purificationcapacityofwaterbodies.Also,itrequireslessinvestmentsupportssimpleandfastconstruction,whichcanlargelyshortentheconstructionperiod.Moreover,thestake-revetmentisasoftrevetment,giventheclimateconditionsofnorthernChinainwinter,thatcansolveproblemscausedbyfrostheaving.Canyousharesomeexperienceonintegratingthedemandforpublicactivitieswithenvironmentalimprovementapproaches?XuQIAO(QIAOhereafter):TheShengxiLakeWetlandParkwhichwecompletedinXiaoyi,Shanxi,canbeseenasamiracleontheLoessPlateau.Xiaoyiisfamousforitscokingcoalproductionwhichhasbroughthugeeconomicbenefits,butalsocausedseverepollution.Alotofash,sandandotherparticulatemattersbroughtbyShengxiLakewetland’supstreamriver,hasresultedinaseriesofproblemslikeextensivesiltation,sharpreductionofstoragecapacity,waterqualitydeterioration,increasedfloodrisks,anddestroyedecologicalenvironment,etc.(Fig.2).Inourlandscapedesignplan,ecologicalrestorationandreconstruction,stormwatersystemmanagement,andplacemakingwereholisticallyintegratedtorestoretheecosystemwhilecreatinganattractiveplaceonahumanscale.Inearly2014,thisdynamic,floatinggardenwithnaturalself-purificationabilitywasshowntothepublic(Fig.3).Differentfromthetypicalurbanpublicgreenspace,herethenaturalizedlandscapecreatesrichseasonalviews,providingvisitorsauniquewaterfrontexperience.Inwetseasons,thepools,waterfalls,andhabitatislandsformacontinuousandflowingwetlandlandscape;indryseasons,rainwatercollectionpoolsbecomethescatteredwetlandpondsinthesite(Fig.4).WhenvisitorsareenjoyingthebeautyofShengxiLake,usuallytheyarenotawareoftheexistenceoftwofunctioninginternalsystems:thewaterresourceregulatorysystemconsistingofsettlingbasin,flooddrainagecanal,andShengxiLakereservoir;andwaterpurificationsystemformedbysettlingbasin,andsurfaceflowwetlands.Thesettlingbasinweredesignedbasedontheanalysisofsedimentdepositiondistributionindifferentfloodingprocesses(Fig.5).Thecrosssectionofsettlingbasinismuchlargerthanthatoftheupperstreamriver,thuswaterflowsslowerthroughthesettlingbasinwherethesedimentcarryingcapacityisreduced.Thereforethesedimentinthewaterflowwouldbesettledinspecificareas;andatthemeantimethewaterself-adjustmentcapabilityandstoragecapacityarealsoimproved.Theflooddrainagecanalwasdesignedtoprotectthecityduringheavystormevents.Thewaterthatisroughlycleanedbysettlingbasin,aswellastherunoffsfromsurroundingvillages,willgetfurtherpurificationintheconstructedwetlands.25rainwaterponds,averaging780mTheenvironmentwearefacingismulti-dimensionalandfullofcomplexity.Thereforeimprovementandrestorationworkshouldbeasystematicprocesswhichrequiresinvolvementinmulti-disciplines.IntheXiaoyiShengxiLakewetlandproject,thedesignteamcooperatedwithexpertsinhydraulicengineering,sedimentationdynamics,ecology,watertreatmentandotherprofessionsandsuccessfullysolvedthesiltationandotherenvironmentalproblemsthroughexplorationonhydrodynamicmodeledsettlingsimulation,wetlandpurificationsystem,habitatrestoration,andstormwatermanagement.Howistheactualperformanceofthewetlandsinoperation?QIAO:Afterthecompletionoftheproject,wehavecontinuouslymonitoredtheperformanceofthewetlands.Recentresultsofwetland’swaterbodiesindifferentlocationsshowthatthewetland,asanintegratedwatertreatmentsystem,hasgreatlyimproveditswaterquality(Fig.7):theconcentrationofpollutantshasprogressivelydecreasedintheprocess,andthetransparencyofthewaterbodieshasvisiblyenhancedincreased.TheabilityofNHThroughaneffectivefeedbackloopmechanism,t