Moderate　chemical　pre-oxidation　of　coagulation　to　remove　algae　without　breakage　of　the　algae　cells　and　release　of　algal　organic　matter　has　been　well　reported,　while　little　was　known　about　moderate　pre-photocatalysis　followed　by　coagulation　on　the　ultrafiltration　performance　and　membrane　fouling　control　during　algae-laden　water　treatment.　Herein,　three　pretreatment　methods　(photocatalysis,　coagulation　and　moderate　pre-photocatalysis-enhanced　coagulation　(PC))　were　investigated　to　reduce　membrane　fouling　during　ultrafiltration　of　algae-laden　water.　Moderate　photocatalysis　by　a　composite　of　Bi2O3-TiO2/PAC　(Bi-doped　TiO2　nano-composites　supported　by　powdered　activated　carbon)　not　only　avoided　algae　cell　breakage　and　controlled　the　release　of　intracellular　organic　matter,　but　also　halved　the　aluminum　sulphate　(AS)　coagulant　dosage,　since　Bi2O3-TiO2/PAC　acted　as　both　a　photocatalyst　and　flocculation　core.　Under　optimal　conditions　(1.2　g/L　Bi2O3-TiO2/PAC　irradiated　under　visible　light　for　20　min　and　0.1　mM　AS),　the　removal　of　OD680,　DOC　and　UV254　were　83.8　%,　60.3　%　and　77.3　%　respectively.　Moderate　photocatalysis　degraded　medium　and　high　molecular　weight　organics　(biopolymers,　humic　substances　and　building　blocks)　to　low　MW　acidic　and　neutral　organics,　resulting　in　effective　removals　of　humic　substances　and　microbial　metabolites　typically　present　in　algal-derived　pollutant.　Following　PC　pre-treatment　with　ultrafiltration,　87.5　%　increase　in　the　final　specific　flux,　96.1　%　reduction　in　irreversible　resistance,　and　a　change　in　the　fouling　mechanism　from　cake　layer　blockage　to　intermediate　blockage.　In　addition,　the　zeta　potential　was　reduced　and　the　interaction　force　between　pollutant-pollutant/membrane　became　a　repulsive　force.　This　work　demonstrates　the　potential　benefits　of　moderate　pre-photocatalysis-enhanced　coagulation　to　remove　algal　contaminants　and　mitigate　ultrafiltration　membrane　fouling.　©　2023