BOD（生物學術語）：

生(sheng)化(hua)(hua)(hua)需氧(yang)(yang)(yang)量(liang)(liang)或生(sheng)化(hua)(hua)(hua)耗氧(yang)(yang)(yang)量(liang)(liang)(一般指五日生(sheng)化(hua)(hua)(hua)需氧(yang)(yang)(yang)量(liang)(liang))，表(biao)示(shi)水(shui)中(zhong)(zhong)有機物(wu)等(deng)需氧(yang)(yang)(yang)污(wu)染物(wu)質(zhi)含量(liang)(liang)的一個綜合指標。說(shuo)明(ming)(ming)水(shui)中(zhong)(zhong)有機物(wu)由于微生(sheng)物(wu)的生(sheng)化(hua)(hua)(hua)作(zuo)用進行氧(yang)(yang)(yang)化(hua)(hua)(hua)分解，使之無機化(hua)(hua)(hua)或氣體(ti)化(hua)(hua)(hua)時所消耗水(shui)中(zhong)(zhong)溶(rong)(rong)解氧(yang)(yang)(yang)的總數量(liang)(liang)。通常情況下(xia)是指水(shui)樣充(chong)滿*密(mi)閉的溶(rong)(rong)解氧(yang)(yang)(yang)瓶中(zhong)(zhong)，在20℃的暗處培養(yang)5d，分別測定培養(yang)前后(hou)水(shui)樣中(zhong)(zhong)溶(rong)(rong)解氧(yang)(yang)(yang)的質(zhi)量(liang)(liang)濃度(du)(du)，由培養(yang)前后(hou)溶(rong)(rong)解氧(yang)(yang)(yang)的質(zhi)量(liang)(liang)濃度(du)(du)之差，計算每(mei)升樣品消耗的溶(rong)(rong)解氧(yang)(yang)(yang)量(liang)(liang)，以BOD5形式表(biao)示(shi)。其單位ppm或毫克/升表(biao)示(shi)。其值越(yue)高說(shuo)明(ming)(ming)水(shui)中(zhong)(zhong)有機污(wu)染物(wu)質(zhi)越(yue)多，污(wu)染也就越(yue)嚴重。

為了(le)使檢(jian)測(ce)資料有(you)可比性，一般規(gui)定(ding)(ding)一個時(shi)間(jian)(jian)(jian)周期(qi)，在這段時(shi)間(jian)(jian)(jian)內，在一定(ding)(ding)溫(wen)度下用(yong)水(shui)樣培養(yang)微生物，并(bing)測(ce)定(ding)(ding)水(shui)中溶解氧消(xiao)耗情況，一般采(cai)用(yong)五天時(shi)間(jian)(jian)(jian)，稱為五日生化需氧量，記(ji)做(zuo)BOD5。數值越大證明水(shui)中含有(you)的有(you)機物越多，因此污染(ran)也越嚴重(zhong)。

BOD，生化需(xu)氧(yang)(yang)量（BOD）是一種環境(jing)監測(ce)指標(biao)，主要(yao)用于監測(ce)水(shui)體(ti)中(zhong)有機物(wu)的(de)(de)污染狀況。一般有機物(wu)都可(ke)以(yi)被(bei)微生物(wu)所(suo)分解，但(dan)微生物(wu)分解水(shui)中(zhong)的(de)(de)有機化合物(wu)時(shi)需(xu)要(yao)消耗(hao)氧(yang)(yang)，如果水(shui)中(zhong)的(de)(de)溶解氧(yang)(yang)不足以(yi)供(gong)給微生物(wu)的(de)(de)需(xu)要(yao)，水(shui)體(ti)就處于污染狀態(tai)。BOD才是有關(guan)環保的(de)(de)指標(biao)。