1.M u:

Nc l nhu cu tt yu ca mi sinh vt. Khng c nc cuc sng trn tri t khng th tn ti c. Hng ngy trung bnh mi ngi cn t 3-10 lt p ng cho nhu cu n ung v sinh hot hng ngy. Trong sinh hot nc cp dng p ng nhu cu sinh hot n ung, v sinh, cac hat ng gii tr, v cac hat ng cng cng nh cu ha, phun nc, ti ngcn trong cng nghip, nc cp c dng cho qu trnh lm lnh, sn xut thc phm nh hp, nc gii kht, ru Hu nh mi ngnh cng nghip u s dng nc cp nh l mt ngun nguyn liu khng g thay th c trong sn xut.

Ty thuc vo mc pht trin cng nghip v mc sinh hot cao thp ca mi cng ng m nhu cu v nc cp vi s lng v cht lng khc nhau.

Ngy nay vi s pht trin ca cng nghip, th v s bng n dn s ngun nc cng ngy b nhim v cn kit.

V th con ngi cn phi bit cch x l cc ngun nc cp p ng c v cht lng ln s lng cho sinh hot hng ngy v sn xut cng nghip.

2. u v nhc im khi s dng nc ngm:

2.1 u im

-Nc ngm l ti nguyn thng xuyn, t chu nh hng ca cc yu t kh hu nh hn hn.

-Cht lng nc tng i n nh, t b bin ng theo ma nh nc mt.

-Ch ng hn trong vn cp nc cho cc vng ho lnh, dn c tha, nht l trong hon cnh hin nay bi v nc ngm c th khai thc vi nhiu cng sut khc nhau.

- khai thc nc ngm c th s dng cc thit b in nh bm ly tm, my nn kh, bm nhng chm hoc cc thit b khng cn in nh cc loi bm tay. Ngoi ra nc ngm cn c khai thc tp trung ti cc nh my nuc ngm, cc x nghip, hoc khai thc phn tn ti cc h dn c. y l u im ni bt ca nc ngm trong vn cp nc nng thn.

-Gi thnh x l nc ngm nhn chung r hn so vi nc mt.

2.2 Nhc im

-Mt s ngun nc ngm tng su c hnh thnh t hng trm, hng nghn nm v ngy nay nhn c rt t s b cp t nc ma. V tng nc ny ni chung khng th ti to hoc kh nng ti to rt hn ch. Do vy trong tng lai cn phi tm ngun nc khc thay th khi cc tng nc ny b cn kit.

-Vic khai thc nc ngm vi qui m v nhp iu qu cao cng s lm cho hm lng mui trong nc tng ln t dn n vic tng chi ph cho vic x l nc trc khi a vo s dng.

-Khai thc nc ngm vi nhp iu cao s lm cho mc nc ngm h thp xung, mt mt lm cho qu trinh nhim mn tng ln, mt khc lm cho nn t b vng xung gy h hi cc cng trnh xy dng-mt trong cc nguyn nhn gy hin tng ln st t.

-Khai thc nc ngm mt cch ba bi cng d dn ti tnh trng nhim ngun nc ngm.

3.Cc phng php x l nc ngm

V nguyn tc nc cha hm lng tp cht dng no ln hn gii hn cho php th phi x l trc khi em s dng. Cho n nay ngi ta x l nc theo cc phng php sau:

X l nc ngm bng phng php c hc

Nc t ngun c bm cp 1 phun qua gin ma thnh nhng tia nh xy ca khng kh tc dng vi Fe2+ thnh Fe3+. Nc dn ma c dn i lng lc cc b lc cha cht lc (ct, , than hot tnh)

X l nc ngm bng phng php ha hc

L phng php dng ha cht, cc phn ng ha hc trong qu trnh x l nc.

Nu nc c c ln chng t cha nhiu cht hu c v sinh vt ph du th dng phn v cht to keo t ngng tp cht.

Nc cha nhiu ion kim loi ( cng ln) x l bng vi, sa hoc dng phng php trao i ion. Nc cha nhiu c t H2S x l bng phng php oxy ha, clo ha, phn.

Nc cha nhiu vi khun th phi kh trng bng cc hp cht cha clo, ozon.

Nc cha Fe th oxy ha Fe2+ bng oxy khng kh (lm thang gin ma) hoc dng cht oxy ha x l

kim ca nc nh lm cho qu trnh keo t kh khn, nc c mi v th phi kim ha bng amoniac (NH3). Sau khi cacbon ha, clo ha s b ri thm KMnO4.

Nc c nhiu oxy ha tan th phi x l bng cch dng cc cht kh lin kt oxy. l hydrazin, natrithisunfat

Nhn chung cc phng php x l ha hc thng t nng sut v c hiu qu cao.

X l nc ngm bng phng php vi sinh

Trn th gii hin nay phng php x l nc bng vi sinh ang c nghin cu v c mt s ni p dng. Trong phng php ny mt s chng loi vi sinh c bit c nui cy v c a vo trong qu trng x l nc vi liu lng rt nh nhng t hiu qu cao. Tuy nhin cho n nay nhng kt qu nghin cu ca phng php ny cha c cng b rng ri.

Ty thuc vo ngun nc lm nguyn liu cho cc lnh vc khc nhau m ngt ta s dung cac phng php khc nhau x l nc cp cho lnnh vc . Thng thng th ngi ta kt hp c 2 phng php c hc v ha hc x l nc.

4. K thut v cng ngh x l nc ngm

4.1 Cc cng trnh thu nc ngm

a. Ging khoan

Ging khoan l cng trnh thu nc ngm mch su vi cng sut trung bnh v ln, c su vi chc n vi trm mt v ng knh ging ph thuc vo lu lng cn khai thc. Ging khoan gm c: ging khoan hon chnh (khoan ti lp cch nc) v ging khoan khng hon chnh (khoan lng chng n lp t cha nc) ging khoan c p v khng p. Khi cn khai thc mt lng nc ln, ngi ta c th dng mt nhm ging khoan, tuy nhin trong trng hp ny cc ging s b nh hng ln nhau khi lm vic ng thi.

b. H thng thu nc ngm tng nng

y l loi cng trnh dng thu nc ngm mch nng nhng ni nc ngm su b nhim mn, vic o ging kh khn.

ng ng thu nc bao gm mt h thng ng thu nc t nm ngang dng c l hoc dng x rnh ng ng, t trong lp t c cha nc, c dc nc t chy v ging tp trung, t y c th dng go mc hoc my bm ly nc. ngn khng cho ct chui vo bn trong ng thu nc, ngi ta thng xp dm, cui, si xung quanh ng.

Trn ng ng a nc v ging tp trung, c khong 25-30m phi b tr mt ging thm kim tra nc, ly cn v thng hi.

c. Phng tin ly nc t ging ln

ly nc t ging ln ngi ta thng s dng gu mc nc bng tay (vi cc ging o khi) hoc cc loi bm ging khc nhau.

Mt trong nhng bm ging ph bin nht vng nng thn l ging bm tay theo m hnh ca UNICEF. bm nc t cc ging khoan qui m nh, ngi ta thng s dng cc loi bm ly tm hoc my nn kh. i vi cc ging khoan qui m cng nghip, ngi ta thng s dng bm ha tin.

Tnh ton thy lc ging ly nc ngm c th chia ra: ging n chic (khng chu nh hng ca cc ging bm khc), v nhm ging bm, vi s b tr c quan h thy lc vi nhau.

4.2 Cng trnh x l st, mangan

Cc phng php kh st, mangan trong nc ngm

a. Kh st, mangan bng phng php lm thong

St, Mangan trong nc thng tn ti dng Fe2+, Mn2+ v vy mun loi chng ra khi nc cn oxy ha chng thnh mui Fe3+, Mn4+ dng t tan ri dng phng php lng, lc d gi chng li v loi chng ra khi nc. Mun oxy ha Fe2+ thnh Fe3+, Mn2+ thnh Mn4+ ngi ta thng s dng phng php lm thong t nhin hay cng bc (cc dn ma hay qut gi). Thc cht ca phng php lm thong l lm giu oxy cho nc, to iu kin cho Fe2+ oxy ho thnh Fe3+ sau Fe3+ thc hin qu trnh thy phn to thnh hp cht t tan Fe(OH)3,Mn2+ thnh MnO2 ri dng b lc gi li.

b. Kh st,mangan bng phng php dng ha cht

Kh st,mangan bng cht oxy ha mnh

- Cc cht oxy mnh thng dng kh st l: Cl2, KMnO4, O3So snh vi phng php kh st bng lm thong ta thy, dng cht oxy ha mnh phn ng xy ra nhanh hn, pH mi trng thp hn (pH