Part 1 Introduction: examples of inappropriate technology; purpose and organization; summary. Part 2 Basic considerations: general design guides for practical water treatment; water quality criteria; choice of source; choice of treatment processes; construction materials and practices - concrete, structural design consideration, alternative construction materials for small plants, valves and gates. Part 3 Pretreatment: plain sedimentation; storage; roughing filtration - vertical flow roughing filters, horizontal flow roughing filters; grit removal; control of microorganisms. Part 4 Chemicals and chemical feeding: the jar test; primary coagulants - alum salts, ferric salts; alkalies for pH control; natural coagulant aids - adsorbents-weighting agents, natural polyelectrolytes; disinfection - gaseous chlorine, hypochlorite compounds, on-site manufacture of disinfectants; chemical feeding - chlorine feeding, solution-feed chlorinators, direct-gas feed chlorinators, solution-type feeders, constant-rate feeders, proportional feeders, saturated solution feeders, dry-chemical feeders, educators. Part 5 Hydraulic rapid mixing: design criteria; rapid mixing devices - hydraulic jump mixers, Parshall flume, Palmer-Bowlus flume, weirs, baffled mixing chambers, hydraulic energy dissipators, turbulent pipe flow mixers; applications of coagulants in open channels; flow-measurement systems in open channels. Part 6 Hydraulic flocculation: design criteria; baffled-channel flocculators; hydraulic jet-action flocculators; gravel bed flocculators; surface contact flocculators. Part 7 Sedimentation: horizontal flow sedimentation - design criteria, inlet arrangement, outlet arrangement, manual sludge removal; inclined plate and tube settling; upflow sedimentation. Part 7 Sedimentation: horizontal flow sedimentation - design criteria, inlet arrangement, outlet arrangement, manual sludge removal; inclined plate and tube settling; upflow sedimentation. Part 8 Filtration: rapid filtration - dual media filters, filter bottom and underdrains, backwashing arrangements, auxiliary-scour wash systems, filter control systems, constant-rate filtration, declining-rate filtration, design and operation of interfilterwashing units, direct filtration, upflow downflow filtration; slow sand filtration - design of slow sand filters, dynamic filtration, information sources on slow sand filtration.(Part contents).