Preparation method of composite flocculating agent for pretreating blue alga biogas slurry

The invention discloses a preparation method of a composite flocculating agent for pretreating blue alga biogas slurry, belonging to the technical field of waste water treatment. The method comprises the following steps of: adding a certain amount of PAC (Poly Aluminum Chloride) solution into a reaction kettle; heating the reaction kettle till the temperature is 60-70 DEG C; slowly adding a certain amount of CTS (Chitosan) which can be dissolved into 1 volume fraction of acetic acid under the continuously stirring condition; reacting for 0.5-1 hour and stopping heating; naturally cooling to the room temperature; and curing at the normal temperature for 24 hours to obtain a PAC-CTS composite flocculating agent. In the method, an inorganic/organic composite flocculating agent is prepared by introducing a natural organic high molecular CTS flocculating agent into an inorganic PAC flocculating agent, so that the inorganic/organic composite flocculating agent has the properties of the natural organic high molecular CTS flocculating agent and the inorganic PAC flocculating agent, the defect of short PAC molecular chain is overcome, large flocculating constituents are formed by bridging amount particles, small particles can be removed by enmeshing, and the capacity of neutralizing surface negative load of particles is enhanced simultaneously. The composite flocculating agent has the advantages of high turbidity removing and phosphorus removing efficiencies, high flocculating speed, small medicament adding amount, small sludge amount and the like.