BOD與COD區別
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1、BOD（Biochemical Oxygen Demand的簡寫(xie)）：生化(hua)(hua)需氧量或(huo)生化(hua)(hua)耗氧量。(五日(ri)化(hua)(hua)學需氧量)表示(shi)水中有機物(wu)等需氧(yang)污染物(wu)質含量的一個綜合指示(shi)。
它說(shuo)明水中有(you)機(ji)物由于微生物的生化作用進行氧(yang)化分解，使之無機(ji)化或(huo)氣體化時所(suo)消耗水中溶(rong)解氧(yang)的總數(shu)量。其(qi)單位ppm成(cheng)毫克/升表(biao)示。其(qi)值越(yue)(yue)高說(shuo)明水中有(you)機(ji)污染物質(zhi)越(yue)(yue)多，污染也(ye)就越(yue)(yue)嚴重(zhong)。
為了(le)使檢測資料有(you)可(ke)比性，一(yi)(yi)(yi)般規定一(yi)(yi)(yi)個時(shi)(shi)間(jian)(jian)周期，在這段時(shi)(shi)間(jian)(jian)內，在一(yi)(yi)(yi)定溫度下用水樣培養微(wei)生物，并(bing)測定水中(zhong)(zhong)溶解氧(yang)消耗(hao)情況，一(yi)(yi)(yi)般采(cai)用五天時(shi)(shi)間(jian)(jian)，稱為五日生化需氧(yang)量，記做(zuo)BOD5。數值(zhi)越大證明(ming)水中(zhong)(zhong)含有(you)的有(you)機物越多，因此污染也越嚴(yan)重。
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2、化學(xue)需氧量COD（Chemical Oxygen Demand）是在一(yi)(yi)定(ding)(ding)(ding)的(de)(de)(de)(de)(de)(de)(de)條件下，采(cai)用(yong)(yong)一(yi)(yi)定(ding)(ding)(ding)的(de)(de)(de)(de)(de)(de)(de)強氧(yang)(yang)化(hua)(hua)劑(ji)處理水(shui)(shui)樣(yang)(yang)時(shi)，所消耗的(de)(de)(de)(de)(de)(de)(de)氧(yang)(yang)化(hua)(hua)劑(ji)量(liang)(liang)。它是表(biao)示水(shui)(shui)中(zhong)(zhong)(zhong)還(huan)(huan)(huan)原(yuan)性(xing)(xing)(xing)物(wu)(wu)(wu)質(zhi)(zhi)(zhi)多少(shao)的(de)(de)(de)(de)(de)(de)(de)一(yi)(yi)個指標(biao)。水(shui)(shui)中(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)還(huan)(huan)(huan)原(yuan)性(xing)(xing)(xing)物(wu)(wu)(wu)質(zhi)(zhi)(zhi)有(you)各種有(you)機(ji)(ji)物(wu)(wu)(wu)、亞硝(xiao)酸鹽、硫化(hua)(hua)物(wu)(wu)(wu)、亞鐵鹽等(deng)。但(dan)主要的(de)(de)(de)(de)(de)(de)(de)是有(you)機(ji)(ji)物(wu)(wu)(wu)。因此，化(hua)(hua)學(xue)需(xu)氧(yang)(yang)量(liang)(liang)（COD）又往往作為(wei)衡量(liang)(liang)水(shui)(shui)中(zhong)(zhong)(zhong)有(you)機(ji)(ji)物(wu)(wu)(wu)質(zhi)(zhi)(zhi)含量(liang)(liang)多少(shao)的(de)(de)(de)(de)(de)(de)(de)指標(biao)。化(hua)(hua)學(xue)需(xu)氧(yang)(yang)量(liang)(liang)越大(da)(da)，說(shuo)明水(shui)(shui)體受有(you)機(ji)(ji)物(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)(de)污(wu)染越嚴重。 化(hua)(hua)學(xue)需(xu)氧(yang)(yang)量(liang)(liang)（COD）的(de)(de)(de)(de)(de)(de)(de)測定(ding)(ding)(ding)，隨著測定(ding)(ding)(ding)水(shui)(shui)樣(yang)(yang)中(zhong)(zhong)(zhong)還(huan)(huan)(huan)原(yuan)性(xing)(xing)(xing)物(wu)(wu)(wu)質(zhi)(zhi)(zhi)以及測定(ding)(ding)(ding)方法(fa)(fa)(fa)的(de)(de)(de)(de)(de)(de)(de)不(bu)同，其測定(ding)(ding)(ding)值(zhi)也有(you)不(bu)同。目前應用(yong)(yong)普遍的(de)(de)(de)(de)(de)(de)(de)是酸性(xing)(xing)(xing)高錳酸鉀(jia)氧(yang)(yang)化(hua)(hua)法(fa)(fa)(fa)與重鉻酸鉀(jia)氧(yang)(yang)化(hua)(hua)法(fa)(fa)(fa)。高錳酸鉀(jia)（KMnO4）法(fa)(fa)(fa)，氧(yang)(yang)化(hua)(hua)率(lv)較(jiao)(jiao)低，但(dan)比較(jiao)(jiao)簡便，在測定(ding)(ding)(ding)水(shui)(shui)樣(yang)(yang)中(zhong)(zhong)(zhong)有(you)機(ji)(ji)物(wu)(wu)(wu)含量(liang)(liang)的(de)(de)(de)(de)(de)(de)(de)相(xiang)對(dui)(dui)比較(jiao)(jiao)值(zhi)及清潔地(di)表(biao)水(shui)(shui)和(he)地(di)下水(shui)(shui)水(shui)(shui)樣(yang)(yang)時(shi)，可(ke)以采(cai)用(yong)(yong)。重鉻酸鉀(jia)（K2Cr2O7）法(fa)(fa)(fa)，氧(yang)(yang)化(hua)(hua)率(lv)高，再現性(xing)(xing)(xing)好(hao)，適用(yong)(yong)于測定(ding)(ding)(ding)水(shui)(shui)樣(yang)(yang)中(zhong)(zhong)(zhong)有(you)機(ji)(ji)物(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)(de)總量(liang)(liang)。 有(you)機(ji)(ji)物(wu)(wu)(wu)對(dui)(dui)工業水(shui)(shui)系(xi)(xi)統(tong)(tong)的(de)(de)(de)(de)(de)(de)(de)危害很大(da)(da)。含有(you)大(da)(da)量(liang)(liang)的(de)(de)(de)(de)(de)(de)(de)有(you)機(ji)(ji)物(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)(de)水(shui)(shui)在通(tong)過除鹽系(xi)(xi)統(tong)(tong)時(shi)會污(wu)染離子交(jiao)換(huan)樹脂(zhi)，容易污(wu)染陰離子交(jiao)換(huan)樹脂(zhi)，使樹脂(zhi)交(jiao)換(huan)能力降(jiang)低。有(you)機(ji)(ji)物(wu)(wu)(wu)在經過預(yu)處理時(shi)（混凝(ning)、澄(cheng)清和(he)過濾），約可(ke)減少(shao)50%，但(dan)在除鹽系(xi)(xi)統(tong)(tong)中(zhong)(zhong)(zhong)無法(fa)(fa)(fa)除去，故常通(tong)過補(bu)給(gei)水(shui)(shui)帶(dai)入鍋(guo)爐，使爐水(shui)(shui)pH值(zhi)降(jiang)低。有(you)時(shi)有(you)機(ji)(ji)物(wu)(wu)(wu)還(huan)(huan)(huan)可(ke)能帶(dai)入蒸汽系(xi)(xi)統(tong)(tong)和(he)凝(ning)結水(shui)(shui)中(zhong)(zhong)(zhong)，使pH降(jiang)低，造成系(xi)(xi)統(tong)(tong)腐蝕。在循(xun)環水(shui)(shui)系(xi)(xi)統(tong)(tong)中(zhong)(zhong)(zhong)有(you)機(ji)(ji)物(wu)(wu)(wu)含量(liang)(liang)高會促進微生物(wu)(wu)(wu)繁(fan)殖。因此，不(bu)管(guan)對(dui)(dui)除鹽、爐水(shui)(shui)或(huo)循(xun)環水(shui)(shui)系(xi)(xi)統(tong)(tong)，COD都是越低越好(hao)，但(dan)并沒有(you)統(tong)(tong)一(yi)(yi)的(de)(de)(de)(de)(de)(de)(de)限制指標(biao)。在循(xun)環冷卻水(shui)(shui)系(xi)(xi)統(tong)(tong)中(zhong)(zhong)(zhong)COD（DmnO4法(fa)(fa)(fa)）>5mg/L時(shi)，水(shui)(shui)質(zhi)(zhi)(zhi)已(yi)開(kai)始變(bian)差(cha)。
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