【摘要】：隨著水資源污染日益加劇,政府對(duì)水質(zhì)監(jiān)測(cè)的力度不斷增強(qiáng),一套具備快速、精確、可在線化監(jiān)測(cè)功能的水質(zhì)監(jiān)測(cè)設(shè)備是提高監(jiān)測(cè)水平和執(zhí)法效率的關(guān)鍵所在.化學(xué)需氧量(COD)是反映水體中有機(jī)還原性污染物含量的重要指標(biāo),它是各國(guó)評(píng)價(jià)水體受污染程度的綜合指標(biāo)之一,所以水質(zhì)COD監(jiān)測(cè)傳感器是一類非常重要的水質(zhì)監(jiān)測(cè)設(shè)備.目前,國(guó)內(nèi)外的水質(zhì)COD監(jiān)測(cè)傳感器種類繁多且性能各異,但檢測(cè)水體COD的主要方法可大致分為兩類:第一類是根據(jù)化學(xué)分析方法來檢測(cè)COD;第二類是通過物理方法進(jìn)行檢測(cè).化學(xué)方法主要以重鉻酸鉀法與高錳酸鹽指數(shù)法為代表,其特點(diǎn)是測(cè)量精度高、耗時(shí)較長(zhǎng)、對(duì)水樣的預(yù)處理過程復(fù)雜、所用化學(xué)試劑易產(chǎn)生二次污染.物理方法主要以紫外吸收法(簡(jiǎn)稱UV法)為代表,其特點(diǎn)是分析靈敏度高、不需要對(duì)水樣進(jìn)行預(yù)處理、無(wú)二次污染、操作簡(jiǎn)便、分析速度快.現(xiàn)如今各水體經(jīng)常有突發(fā)性水污染事件發(fā)生,而且對(duì)水質(zhì)的監(jiān)測(cè)不能間斷,所以用化學(xué)分析方法設(shè)計(jì)出的水質(zhì)COD監(jiān)測(cè)傳感器已經(jīng)不能滿足上述要求了.同時(shí),以紫外吸收法為原理所設(shè)計(jì)的水質(zhì)COD監(jiān)測(cè)傳感器也還存在很多缺陷,所以本文的研究目的是改進(jìn)以紫外吸收法為原理的光譜水質(zhì)COD監(jiān)測(cè)傳感器的算法,進(jìn)而使COD光譜監(jiān)測(cè)傳感器的測(cè)量精度提高、適用范圍拓廣,以便生產(chǎn)出準(zhǔn)確、方便、可在線化連續(xù)監(jiān)測(cè)的水質(zhì)傳感器.本文首先系統(tǒng)地介紹了紫外吸收法的基本原理,以及紫外吸收法中幾種常用方法的發(fā)展歷程和優(yōu)缺點(diǎn),并詳細(xì)介紹了偏最小二乘回歸的基本原理和相關(guān)性質(zhì).本文分析了前人的研究成果,在以前的研究中很多研究者是用待測(cè)液體在某一特定波長(zhǎng)處的紫外吸光度來預(yù)測(cè)水樣中的COD值:也有一部分研究者在此基礎(chǔ)上考慮了濁度對(duì)特定波長(zhǎng)處吸光度的影響,并對(duì)該特定波長(zhǎng)的吸光度做了濁度補(bǔ)償:還有一部分研究者是考慮用待測(cè)液體在多個(gè)指定波長(zhǎng)處的吸光度來預(yù)測(cè)水樣的COD值,但還沒有研究者考慮過用待測(cè)液體在多個(gè)指定波長(zhǎng)處的吸光度建模的同時(shí)又考慮濁度的影響.為了進(jìn)一步提高COD監(jiān)測(cè)的準(zhǔn)確性和適用范圍,本文提出了一種基于偏最小二乘回歸和濁度補(bǔ)償?shù)腃OD檢測(cè)算法.該算法是通過將全光譜吸光度檢測(cè)法與偏最小二乘回歸相結(jié)合來預(yù)測(cè)水體中的化學(xué)需氧量,同時(shí)考慮了濁度對(duì)建模所使用的吸光度(自變量)的影響,并對(duì)濁度的影響進(jìn)行了補(bǔ)償.通過實(shí)驗(yàn)分析表明:該方法對(duì)不同類型的污水均適用,檢測(cè)的平均相對(duì)誤差在5%以內(nèi),而且通過對(duì)比發(fā)現(xiàn)模型的預(yù)測(cè)精度明顯優(yōu)于未經(jīng)濁度補(bǔ)償?shù)钠钚《嘶貧w模型,這為開發(fā)出一款適應(yīng)性強(qiáng)且可在線化監(jiān)測(cè)的水質(zhì)COD傳感器提供了算法依據(jù).
[Abstract]:With the increasing pollution of water resources, the government is increasing the intensity of water quality monitoring. A set of water quality monitoring equipment with rapid, accurate and on-line monitoring function is the key to improve the monitoring level and law enforcement efficiency. Chemical oxygen demand (COD) is an important index to reflect the content of organic reducing pollutants in water. It is one of the comprehensive indexes to evaluate the degree of water pollution in various countries, so the water quality COD monitoring sensor is a kind of very important water quality monitoring equipment. At present, there are many kinds of water quality COD monitoring sensors at home and abroad, but the main methods of detecting water COD can be divided into two categories: the first is to detect COD; by chemical analysis method, and the second is to detect COD; by physical method. The chemical methods are mainly represented by potassium dichromate method and permanganate index method, which are characterized by high measurement accuracy, long time consuming, complex pretreatment process of water samples and easy secondary pollution of the chemical reagents used. The physical method is mainly represented by ultraviolet absorption method (UV), which is characterized by high analytical sensitivity, no pretreatment of water sample, no secondary pollution, simple operation and fast analysis speed. Nowadays, there are often sudden water pollution events in various water bodies, and the monitoring of water quality can not be interrupted. Therefore, the water quality COD monitoring sensor designed by chemical analysis method can not meet the above requirements. At the same time, the design of water quality COD monitoring sensor based on ultraviolet absorption method also has many defects, so the purpose of this paper is to improve the algorithm of spectrum water quality COD monitoring sensor based on ultraviolet absorption method. Thus, the measurement accuracy of the COD spectrum monitoring sensor is improved and the applicable range is extended to produce an accurate, convenient and on-line water quality sensor for continuous monitoring. In this paper, the basic principle of ultraviolet absorption method is introduced systematically, and the development history, advantages and disadvantages of several common methods in ultraviolet absorption method are introduced, and the basic principle and related properties of partial least square regression are introduced in detail. In this paper, the previous research results are analyzed. In previous studies, many researchers have used the UV absorbance of the liquid to be measured at a particular wavelength to predict the COD value in water samples: some researchers have also considered the effect of turbidity on absorbance at a particular wavelength. And the turbidity compensation for the absorbance of the specific wavelength is given: some researchers are considering using the absorbance of the liquid to be measured at several specified wavelengths to predict the COD value of the water sample. However, no researchers have considered the effect of turbidity on the absorbance modeling of the liquid to be tested at several specified wavelengths at the same time. In order to improve the accuracy and application range of COD monitoring, a COD detection algorithm based on partial least square regression and turbidity compensation is proposed in this paper. In this algorithm, the full spectral absorbance detection method and partial least square regression are combined to predict the chemical oxygen demand (COD) in water, and the influence of turbidity on the absorbance (independent variable) used in modeling is considered. The effect of turbidity is compensated. The experimental results show that the method is suitable for different types of sewage, and the average relative error is less than 5%, and the prediction accuracy of the model is obviously better than that of the partial least square regression model without turbidity compensation. This provides an algorithm basis for the development of an adaptive and on-line water quality COD sensor.
【學(xué)位授予單位】：四川師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TP212

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